Rust species classified in Ochropsora, Aplopsora, and Cerotelium pro parte were re-examined and re-circumscribed by morphology, host preference, life cycle pattern, and geographic distribution. Macrocyclic heteroecious life cycle was proven for seven species by field observations and experimental inoculations. Partial molecular phylogenetic analyses were also included in the taxonomic decision. Anamorphic fungi and others, that were newly discovered and assumed to be related to these genera, were also examined in the same manner. Aplopsora was synonymized under Ochropsora. One fungus named under Cerotelium and two anamorphic fungi were determined as species of Ochropsora. Fifteen species were recognized in Ochropsora: O. ariae, O. asari, O. asiatica, O. corni, O. cumminsii, O. ehimensis, O. dicentrae, O. kraunhiae, O. laporteae, O. lonicerae, O. nambuana, O. nyssae, O. panacis, O. staphyleae, and O. tanakae. Most of Ochropsora species are distributed in eastern Asia. Only O. ariae is known in northwestern Europe and O. cumminsii, O. dicentrae, and O. nyssae are known in eastern North America. The disjunct distribution of Ochropsora in the Northern Hemisphere is interpretated by disjunctions of ancestral species once broadly distributed in the Northern Hemisphere and subsequent species diversification, migration, and extinction in each of the three geographic regions.

The typification, nomenclature, and phylogenetic taxonomy of the genera Ochropsora and Aplopsora have been complicated without a universally acceptable solution for classification of their species and their generic status in the Pucciniales. This complication is largely because species, that would have been classified in these genera, have been poorly explored and because biological nature of these species has been insufficiently studied. The genus Ochropsora was proposed by Dietel (1895) based on Melampsora sorbi (Oudem.) G. Winter parasitic on Sorbus aucuparia L. (Rosaceae) in northwestern Europe (Oudemans, 1872). Ramsbottom (1914) proposed, however, to replace O. sorbi (Oudem.) Dietel with O. ariae (Fuckel) Ramsb. as the correct name of the type species of the genus. The fungus parasitic on S. aria Crantz originally named as Melampsora ariae Fuckel (Fuckel, 1870, cited from Ramsbottom, 1914) was found to be conspecific with O. sorbi., and the former name predated the latter. Ochropsora ariae was characterized by sessile, one-celled, cylindrical, and laterally free teliospores and by the unique mode of basidium development from a teliospore, i.e., a teliospore turned into a four-celled basidium with little morphological change (often referred to as “internal mode of teliospore germination”) (Cummins & Hiratsuka, 2003; Soong, 1939; Winter, 1884). Close taxonomic relationships of the genus Ochropsora to the genus Aplopsora have been assumed (Dietel, 1923; Ono, 2006). The genus Aplopsora was proposed by Mains (1921) based on Uredo nyssae Ellis & Tracy parasitic on Nyssa aquatica L. (Cornaceae) in eastern North America. Aplopsora nyssae was characterized by sessile, one-celled, cylindrical, thin-walled, and laterally free teliospores, as in O. ariae. However, the mode of basidium development was different from that of O. ariae: a teliospore of A. nyssae elongated apically to become a four-celled basidium in situ (often referred to as “external mode of teliospore germination”) (Cummins & Hiratsuka, 2003; Mains, 1921). Because of the similarity in structural characteristics of uredinia and morphology of teliospores, despite the different mode of basidium development, Dietel (1923) assumed that Ochropsora and Aplopsora probably shared a most recent common ancestor.

As the number of species described for these genera increased, the generic character of “internal” basidium development for the genus Ochropsora became questioned (Ono, 2006). The exact mode of teliospore production and basidium development were not determined in most of the species. Before this study, four species were recognized for Ochropsora: O. ariae (Fuckel) Ramsb. on Amelanchier, Aruncus, Sorbus, and other rosaceous plants in northwestern Europe and eastern Asia; O. daisenensis T. Hirats. & S. Uchida on Panax (Araliaceae) in eastern Asia (including the eastern extension of the Himalayas), O. krauhniae (Dietel) Dietel on Wisteria (Fabaceae) in Japan, and O. nambuana (Henn.) Dietel on Elaeagnus (Elaeagnaceae) in eastern Asia. The characteristic “internal mode” of basidium development was not clearly documented in these species other than northwestern European O. ariae. For the genus Aplopsora, five species were recognized: A. corni Y. Ono & Y. Harada on Cornus (Cornaceae) in Japan, A. dicentrae (Trel.) Buriticá & J.F. Hennen on Laportea (Urticaceae) in eastern North America, A. lonicerae Tranzschel on Lonicera (Caprifoliaceae) in eastern Asia, A. nyssae (Ellis & Tracy) Mains on Nyssa (Cornaceae) in eastern North America, and A. tanakae (S. Ito) Buriticá & J.F. Hennen on Amphicarpaea (Fabaceae) in eastern Asia and eastern North America. External development of a basidium from a teliospore was observed or expected in all these species.

Most species in the two genera had been known only from uredinial and telial stages and, thus, had not been well circumscribed due to structural and morphological simplicity of the observed spore stages, particularly teliospores. The teliospore of species in the two genera are thin-walled, continuously develop into a basidium to produce basidiospores without dormancy and collapse quickly. Therefore, determining the exact mode of teliospore production and measuring mature, intact teliospores and basidia are often difficult (Ono, 2006). Observations and description in the literature are often simple, sometimes not accurate or even erroneous. These difficulties have made taxonomic characterization of the genera and species sometimes inevitably arbitrary. Taxonomic decision based on poor morphological characterization has also brought about the difficulty in the generic characterization and species classification of Cerotelium (Buriticá, 1999; Ono, 1995a; Ono et al., 1992). Species of Cerotelium produce thin-walled, one-celled teliospores in chain from a basal sporogenous cell on a telial hymenium. Although the teliospore chains are compacted in small sori, they are laterally free and become easily separable at the upper part of teliospore chains (Ono et al., 1992). Some rust fungi classified in Cerotelium were later found to have teliospores that were distinct from the genus in developmental morphology (Ono et al., 1992). Making a thin section parallel to a longitudinal axis of teliospores for microscopic observation is not easy, and the thin sections are often obliquely made in a small compacted sorus. This would have resulted in erroneous description on the developmental teliospore morphology: one-celled cylindrical teliospores aligned in a single layer on a telial hymenium were interpreted as if one-celled, ellipsoid to oblong-ellipsoid teliospores produced in chains in the oblique sections of the telium. Apparently, this was the reason why Cerotelium asari S. Kaneko, Katum. & Hirats. f. (Ono, 1995a) and C. dicentrae (Trel.) Mains & H.W. Anderson (Buriticá, 1998) were inappropriately named under Cerotelium. It is also possible that microscopically observed “internally developed basidia” are artefact resulting from oblique sectioning of the telium. Therefore, close re-examination and critical evaluation of morphological features of the telial and uredinial stages of currently recognized species in Ochropsora, Aplopsora, and other morphologically similar genera, like Cerotelium, were needed.

In addition, disclosing complete life cycle with specific host preference is mandatory for the accurate delimitation of the species and genera and for the meaningful molecular phylogenetic analysis to accurately position them in the Pucciniales as suggested by Ono (2006). Before this study began in 1993, complete macrocyclic, heteroecious life cycle was known only for O. ariae and O. krauhniae in Ochropsora. The former species host-alternates to Anemone (Ranunculaceae) and the latter to Corydalis (Papaveraceae). Their spermogonia are subcuticular with flat hymenium (type 7; Cummins & Hiratsuka, 2003), and aecia are cup-shaped with well-developed peridium (Aecidium-type; Cummins & Hiratsuka, 2003). In Aplopsora, complete macrocyclic, heteroecious life cycle was known only for A. dicentrae. Its spermogonial and aecial host is Dicentra cucullaria (L.) Bernh. (Papaveraceae). The spermogonial and aecial morphology are similar to those of Ochropsora species.

This study aimed at taxonomic delimitation of the genera and species previously classified in Ochropsora, Aplopsora, and Cerotelium p.p. by all available data on the complete life cycle, host preference, developmental morphology of all spore stages, and geographic distribution. Aplopsora hennenii Dianese & L.T.P. Santos and A. qualeae Buriticá & Hennen were excluded from the study because these fungi were found conspecific and classified in a new genus Cerradopsora: Cerradopsora hennenii (Dianese & Santos) Ebinghaus & Dianese (Ebinghaus et al., 2023). The greatest emphasis was placed on revealing host preference and complete life cycle of those fungi by continued field observations and experimental inoculations. Molecular phylogenetic analyses of these fungi are still underway. Only limited reliable molecular data were incorporated in the taxonomic discussion.

The genus names of rust fungi and their host plants are fully spelled out when appearing for the first time in the text and at the sentence head, otherwise shortened in the text (Table 1).

Herbarium specimens deposited in the following ten mycological herbaria/fungarium were examined: Botanischer Garten und Botanisches Museum Berlin-Dahlem, Freie Universtät, Germany (B); Conservatoire et jardin botaniques de la ville de Genève, Switzerland (G); the Hiratsuka Herbarium, Japan (HH); the Komarov Botanical Institute, Russia (LE); the College of Education, Ibaraki University, Japan (IBAR); the Department of Botany and Plant Pathology, Purdue University, U. S. A. (PUR); the Swedish Museum of Natural History, Sweden (S); the University of Hokkaido, Japan (SAPA); the University of Tsukuba, Japan (TSH); and Eidgenössische Technische Hochschule Zürich, Switzerland (ZT).

Ochropsora ariae (Fuckel) Ramsb. - Uredinial and telial stages: one on Aruncus dioicus (Walter) Fernald. from Poland; three on the same host from Switzerland; one on Pyrus communis L. from Switzerland; one on Sorbus aria (L.) Crantz from Germany (holotype of Melampsora ariae Fuckel in G); two on S. aucuparia L. from the Netherlands (holotype of Caeoma sorbi Oudemans. in G) and Switzerland; two on Sorbus torminalis (L.) Crantz from Switzerland and Germany.

Ochropsora asari (S. Kaneko, Katum. & Hirats. f.) Y. Ono (= Cerotelium asari S. Kaneko, Katum. & Hirats. f.) - Spermogonial and aecial stages: five on Corydalis lineariloba Siebold & Zucc. (Papaveraceae) from Japan. Uredinial and telial stages: ten on Asarum caulescens Maxim. (Aristolochiaceae) from Japan, including holotype (in HH) and isotype (in YAM).

Ochropsora asiatica Y. Ono - Spermogonial and aecial stages: three on Anemone nikoensis Maxim. (Ranunculaceae) from Japan; twelve on An. pseudoaltaica H. Hara from Japan. Uredinial and telial stages: ten on Aru. sylvester Kostel. ex Maxim. (= Aru. dioicus var. kamtschaticus (Maxim.) H. Hara) (Rosaceae) from Japan, including holotype (in IBAR); seven on the same host from Russia; two on Amelanchier asiatica (Siebold & Zucc.) Endl. ex Walp. (Rosaceae) from Japan; and one on Aria japonica Decne. (= S. japonica (Decne.) Hedl.) (Rosaceae) from Japan.

Ochropsora corni (Y. Ono & Y. Harada) Y. Ono (= Aplopsora corni Y. Ono & Y. Harada) - Spermogonial and aecial stages: eleven on An. raddeana Regel (Ranunculaceae) from Japan. Uredinial and telial stages: eleven on Cornus controversa Hemsl. ex Prain (Cornaceae) from Japan, including holotype (in IBAR).

Ochropsora cumminsii Y. Ono - Probable spermogonial and aecial stages: one on Dicentra cucullaria (L.) Bernh. (Papaveraceae) from U. S. A. Uredinial and telial stages: four on Amphicarpaea bracteata (L.) Fernald (Fabaceae) from U. S. A., including holotype (in IBAR).

Ochropsora dicentrae (Trel.) Y. Ono (= Cerotelium dicentrae (Trel.) Mains & H.W. Anderson) - Spermogonial and aecial stages: three on D. cucullaria (Papaveraceae) from U. S. A. Uredinial and telial stages: five on Laportea canadensis (L.) Wedd. (Urticaceae) from U. S. A.

Ochropsora ehimensis Y. Ono - Uredinial and telial stages: one (holotype in IBAR) on Amp. edgeworthii var. japonica Oliver (Fabaceae) from Japan.

Ochropsora kraunhiae (Dietel) Dietel - Spermogonial and aecial stages: nineteen on Cory. incisa (Thunb.) Pers. (Papaveraceae) from Japan. Uredinial and telial stages: four on Wisteria brachybotrys Siebold & Zucc. (Fabaceae) from Japan; and eighteen on W. floribunda (Willd.) DC. from Japan.

Ochropsora laporteae (Hirats. f.) Y. Ono (= Uredo laporteae Hirats. f.) - Spermogonial and aecial stages: eight on An. flaccida Fr. Schmidt (Ranunculaceae) from Japan. Uredinial and telial stages: thirteen on La. bulbifera (Siebold & Zucc.) Wedd. (Urticaceae) from Japan, including epitype (in IBAR).

Ochropsora lonicerae (Tranzschel) Y. Ono (= Aplopsora lonicerae Tranzschel) - Spermogonial and aecial stages: two on An. nikoensis from Japan; seven on An. pseudoaltaica from Japan. Uredinial and telial stages: eleven on Lonicera gracilipes var. glabra Miq. (Caprifoliaceae) from Japan; one on Lo. maximowiczii (Rupr.) Regel from China; and two on the same host from Russia (lectotype in LE and isolectotype in PUR).

Ochropsora nambuana (Henn.) Dietel - Spermogonial and aecial stages: nineteen on An. flaccida (Ranunculaceae) from Japan. Uredinial and telial stages: eight on Elaeagnus multiflora Thunb. (Elaeagnaceae) from Japan; and nine on E. umbellata Thunb. from Japan, including holotype (in B) and isotype (in SAPA), and holotype of Ceraceopsora elaeagni (in TSH).

Ochropsora nyssae (Ellis & Tracy) Y. Ono (= Aplopsora nyssae Mains) - Uredinial and telial stages: one on Camptotheca acuminata Decne. (Cornaceae) from U. S. A.; two on Nyssa aquatica L. (Cornaceae) from U. S. A., including isotype (in PUR); and five on N. sylvatica Marsh. from U. S. A.

Ochropsora panacis (Syd. & P. Syd.) Y. Ono (= Uredo panacis Syd. & P. Syd.; O. daisenensis T. Hirats. & S. Uchida) - Uredinial and telial stages: three on Panax pseudoginseng Wall. (Araliaceae) from India (holotype of Uredo panacis Syd. & P. Syd. in B and isotypes in S); and one on Pa. japonicus (T. Nees) C.A. Mey. from Japan (holotype of O. daisenensis T. Hirats. & S. Uchida in HH).

Ochropsora staphyleae Y. Ono, Chatasiri & E. Tanaka - Telial stage: five on Staphylea bumalda DC. (Staphyleaceae) from Japan, including holotype (in IBAR).

Ochropsora tanakae (S. Ito) Y. Ono (= A. tanakae (S. Ito) Buriticá & J.F. Hennen) - Spermogonial and aecial stages: twelve on Cory. fumariifolia subsp. azurea Lidén & Zetterl. (Papaveraceae) from Japan. Uredinial and telial stages: eight on Amp. edgeworthii var. japonica (Fabaceae) from Japan; and one on the same host from Russia.

Experimental inoculations to determine a complete life cycle and host preferences were carried out for species of Ochropsora, Aplopsora, and Cerotelium p.p. only distributed in Japan. The reason for this limited experimental inoculation was largely because of plant quarantine regulations and technical difficulties. Both living rust fungi and their potential host plants were not easily introduced from northwestern Europe and eastern North America and grown in Japan. The complete life cycle of O. ariae in northwestern Europe and A. dicentrae in eastern North America have been well confirmed and, thus, no trial was considered. However, a complete life cycle of A. nyssae (the type species of Aplopsora) has remained unknown. The inoculations were carried out from May 1993 through Jun 2020 at Ibaraki University campus, in Mito, Ibaraki, Japan. The complete life cycle of species of Ochropsora (herein inclusive of Aplopsora and Cerotelium p.p.) have been poorly explored. Successful experimental inoculations with aeciospores have proven a macrocyclic, heteroecious life cycle only for O. ariae (Fischer, 1904, 1910; Klebahn, 1907; Tranzschel, 1903, 1904), O. krauhniae (Hiratsuka & Kaneko, 1978), O. nambuana (Henn.) Dietel (Ono, 2006), and A. dicentrae (Mains, 1921). From these studies, species of Ochropsora, Aplopsora, and Cerotelium p.p. were assumed to possess a macrocyclic life cycle and host-alternate to spermogonial-aecial host plants either in the genus Anemone (Ranunculaceae) or the genus Corydalis (Papaveraceae) in Japan. From long-term empirical observations on eco-geographical association and habitat sharing between aecium-bearing ranunculaceous or papaveraceous plants and Ochropsora- or Aplopsora-infected plants in Japan, the source of inocula were focused on An. flaccida, An. nikoensis, An. pseudoaltaica and An. raddeana in Ranunculaceae and Cory. fumariifolia subsp. azurea and Cory. lineariloba in Papaveraceae (Supplementary Table S1).

The aecium-bearing plants were collected at various sites (Supplementary List S1) and planted in clay pots of 18 cm or 21 cm diam, depending on their sizes, with loam or sandy loam soil. The potted plants had been maintained at the experimental plot, Ibaraki University campus in Mito, Ibaraki, Japan. The potential uredinial and telial host plants to be inoculated with aeciospores were Ame. asiatica, Ari. japonica and Aru. silvester (Rosaceae), Amp. edgeworthii var. japonica (Fabaceae), As. caulescens (Aristolochiaceae), Corn. controversa (Cornaceae), E. glabra Thunb., E. macrophylla Thunb., E. multiflora Thunb. and E. umbellata Thunb. (Elaeagnaceae), La. bulbifera (Urticaceae), Lo. gracilipes var. glabra (Caprifoliaceae), Pa. japonicus (Araliaceae), and St. bumalda (Staphyleaceae). Prunus buergeriana Miq. and Pr. grayana Maxim. (Rosaceae) were also inoculated, because these trees had been reported as the host of Tranzschelia species, whose spermogonial-aecial stages occurred on Anemone species. These potential uredinial and telial host plants were collected and maintained in the same way as in the spermogonial and aecial host plants. Macrocyclic heteroecious life cycle of O. kraunhiae, host-alternating between Cory. incisa and W. floribunda, was proven before this study initiated (Hiratsuka & Kaneko, 1978). Thus, no additional experimental inoculation with aeciospores produced on Cory. incisa was carried out.

Experimental inoculations were undertaken exclusively by using aeciospores as inocula, and basidiospore inoculation was excluded (see the Discussion section for reasoning). The ranunculaceous or papaveraceous plants, that produce aecia and aeciospores, represent early forest-floor perennial herbs of ephemeral nature in the spring under cool-temperate deciduous and warm-temperate mixed hardwood forests. They survive by underground rhizomes, tubers or bulbs/bulblets, that remain systemically infected by the rust fungi, in the rest of seasons. An advantage of the aeciospore inoculations comes from the perennial nature of spermogonial-aecial host plants and the systemic infection of the fungal mycelia in the hosts’ underground organs. Thus, the fungi under study can persist for a long period of time, i.e., over 20 y in this research. Aecial inocula were repeatedly and readily available in the early spring from the rust-infected ranunculaceous and papaveraceous plants, that had been potted and grown at the experimental plot, Ibaraki University campus, in Mito. However, number of sporulating leaves emerging from each pot and amount of sori and spores produced on the leaves varied and, therefore, experimental aeciospore inoculations were possible only when the sporulation was copious. Inoculations were carried out by a filter-paper method described by Ono (1995a, b) and Ono and Azbukina (1997). Each aecial sample from a total of forty-five aecium-bearing Anemone and Corydalis plants was inoculated onto apparently healthy plants of a maximum of ten potential uredinial-telial host species. However, depending on availability and leaf conditions, not all plants of the ten species were always inoculated at each of separate experimental inoculations.

Methods for making slide preparations, microscopic observations, and photomicrography followed those described by Ono et al. (2020b). To examine the structure and morphology and to measure the size of spermogonia, aecia, teliospores, and basidia, dried herbarium specimens were freehand sectioned under a binocular dissecting microscope. Thin sections were mounted in a drop of lactophenol solution without stain. To examine morphology and to measure size, aeciospores, uredinial paraphyses, and urediniospores were scraped from sori on herbarium specimens and mounted as described above. For those fungi whose urediniospore germ pores were not apparent in the lactophenol-mounted slide preparations, the spores were placed in a drop of lactic acid and heated to boil, and subsequently added a drop of lactophenol solution with/without aniline blue before placing a cover slip over the treated spores. Ten arbitrarily selected spermogonia and twenty arbitrarily selected aeciospores, urediniospores, teliospores, basidia, and paraphyses were measured under either Olympus BX50 or BX51 microscope (Olympus, Tokyo, Japan) with both bright-field and differential interference contrast (DIC) devises. Photomicrographs were taken with an Olympus PM20 automatic photomicrograph unit installed on the BX50 microscope or an Olympus DP21 camera (Olympus, Tokyo, Japan) installed on the BX51 microscope.

For scanning electron microscopy, sorus-bearing pieces of herbarium specimens or spores scraped from herbarium specimens were placed on double-sided adhesive tape on a specimen holder and then coated with platinum-palladium to a 25 nm thicknesses using a Hitachi E-1030 ion sputter (Hitachi, Tokyo, Japan). These samples were observed with a Hitachi S-4200 SEM (Hitachi, Tokyo, Japan) operating at 15 kV.

Thirty-two successful results with Ochropsora sporulations and two successful results with Tranzschelia sporulations were obtained in a total of eighty-five experimental inoculations carried out between the years of 1993 and 2020 (Supplementary Table S1; the host alternation of Tranzschelia species will not be further discussed in this paper; cf. Ono, 2006). In these experimental inoculations, macrocyclic heteroecious life cycle was proven for three species of Ochropsora and four of former Aplopsora species (including a species formerly classified in Cerotelium) (Supplementary Table S1). Spermogonial-aecial stages of the Laportea fungus and the Elaeagnus fungus were produced on An. flaccida. The two aecial fungi on An. flaccida were segregated by their distinct host preference, parasitizing either Laportea or Elaeagus leaves; namely, aeciospores produced on individuals of An. flaccida, that infected and sporulated on Laportea, did not infect and sporulate on Elaeagnus, and those produced on the other individuals of An. flaccida, that infected and sporulated on Elaeagnus, did not infect and sporulate on Laportea. The spermogonial-aecial stages of the two fungi were easily distinguishable by their parasitic habit, i.e., the former species produced spermogonia only on the adaxial leaf surface, while the latter on both leaf surfaces. The same complex parasitic habit was observed in the fungus on Aruncus and other rosaceous plants and the Lonicera fungus, whose spermogonial-aecial stages occurred on An. nikoensis and An. pseudoaltaica. The two fungi were easily segregated by their distinct host preference, parasitizing either Rosaceae or Lonicera plants; namely, aeciospores produced on individuals of An. nikoensis and An. pseudoaltaica, that infected and sporulated on Amelanchier, Aruncus, and Sorbus (Rosaceae), did not infect and sporulate on Lonicera, and those produced on the other individuals of An. nikoensis and An. pseudoaltaica, that infected and sporulated on Lonicera, did not infect and sporulate on the rosaceous plants. The spermogonial-aecial stages of the two fungi were distinguishable by the sizes of aeciospores, i.e., the former species produced small aeciospores (14-22(-27) × 11-18 µm), while the latter large aeciospores (19-28 × 15-24 µm), although both species produced the spermogonia only on the adaxial leaf surface of the two Anemone species. These experimental inoculations clarified that An. flaccida, An. nikoensis and An. pseudoaltaica served as the spermogonial-aecial hosts of the two or more distinct rust species If Tranzschelia is taken into consideration, An. pseudoaltaica is the spermogonial-aecial host of three distinct species in two different genera of rust fungi (cf. Ono, 2006). By contrast, the Cornus fungus formed spermogonial-aecial stages only on An. raddeana. The spermogonial-aecial fungus on An. raddeana did not infect and sporulate on any other potential uredinial/telial hosts inoculated.

In contrast to the spermogonial-aecial fungi on Anemone species, a spermogonial-aecial fungus on Cory. lineariloba infected and sporulated only on As. caulescens. Thus, the Asarum fungus was proven to host-alternate between Cory. lineariloba and As. caulescens. Similarly, the Amphicarpaea fungus (exclusive of one from Pref. Ehime) was proven to host-alternate between Cory. fumariifolia subsp. azurea and Amp. edgeworthii var. japonica. The spermogonial-aecial fungus on Cory. fumariifolia subsp. azurea infected and sporulated on Amp. edgeworthii var. japonica, but not any other potential uredinial-telial host plants inoculated. Life cycle connection between spermogonial-aecial stages on Anemone or Corydalis and uredinial-telial stages on Pa. japonicus was not possible. The Panax fungus has been known only from the type locality, Mt. Daisen, Tottori, in Japan. Several visits to the type locality failed finding the spermogonial-aecial stages on Anemone or Corydalis growing nearby Pa. japonicus. Even Ochropsora-infected Panax plants were not found there in a few visits in different seasons and years. Ochropsora staphyleae was found for the first time in the course of this study and known only from a telial stage. Several experimental inoculations with aeciospores produced on An. nikoensis and An. pseudoaltaica, which were growing nearby the rust-infected Staphylea plants, were unsuccessful (cf. Ono et al., 2020a). After the successful life cycle connections either to Anemone or Corydalis species, it became possible to circumscribe majority of species that had been classified in Ochropsora, Aplopsora, and Cerotelium p.p. in Japan by the distinct life cycle with specific spermogonial-aecial and uredinial-telial host combinations.

Ochropsora and Aplopsora species under study were found to be distinct in combinations of infection habits on their spermogonial-aecial host plants, uredinial-telial host preference, and morphological characteristics. The species, for which a complete life cycle was confirmed, were specifically host-alternating to either ranunculaceous plants (Anemone) or papaveraceous plants (Corydalis or Dicentra), producing spermogonia and aecia on them. The spermogonial-aecial infection was systemic as mentioned above and a whole or large part of leaves arising from rust-infected underground organs became covered with spermogonia and aecia. Spermogonia were formed exclusively on the adaxial, abaxial or both leaf surfaces depending on the species. They were subcuticular, conical, dome-shaped or disc-shaped with a flat hymenium (type 7; Hiratsuka & Hiratsuka, 1980). Aecia were subepidermal in origin, Aecidium-type, and cupulate surrounded with well-developed peridium. Aeciospores were produced in basipetal succession from a basal sporogenous cell layer, thin-walled, uniformly verrucose or weakly bizonate with moderate verrucae above and minute verrucae near the base. The Cornus fungus was the only exception, however. Its aeciospores were verrucose and bizonate with lager verrucae or refractive granules of various sizes on the upper half, the characteristics reminiscent of Tranzschelia aeciospores produced on Hepatica (a close relative of Anemone, Ranunculaceae) in eastern Asia (Ono, 1994) and eastern North America (Lopez-Franco & Hennen, 1990).

Uredinia were scattered or loosely to densely aggregate on the abaxial leaf surface or on both surfaces, subepidermal in origin, and soon became erumpent. They were surrounded densely by paraphyses, which arose from basal pseudoparenchymatous mycelial masses (Malupa-type; Ono et al., 1992). Paraphyses varied from thin-walled to conspicuously thick-walled and not to strongly incurved depending on the species. Only exception was O. panacis, whose uredinia were Uredo-type without paraphyses. Urediniospores were produced singly on a pedicel, subglobose, broadly ellipsoid, obovoid or oblong-ellipsoid, and echinulate. Urediniospore germ pores were usually inconspicuous, and their number and distribution were variable among the species.

Telia were also subepidermal in origin and not paraphysate. They remained covered with the host epidermis until basidia matured to emerge through ruptured host epidermis. Teliospores were one-celled, thin-walled, and short oblong-ellipsoid to long cylindrical. They were produced from a basal sporogenous cell, which might or might not be conspicuous, and appear compact in cross section of sori. However, they were laterally free and easily separable without disrupting their morphology. Four-celled basidia developed from the teliospores by continuous apical elongation in all species, excepting northwestern European O. ariae and the Panax fungus. They developed a four-celled basidium from teliospores with little morphological change. Basidiospores were subglobose, broadly ellipsoid or obovoid, and thin-walled.

Ochropsora Dietel, Ber. Deutch. Bot. Ges. 13: 401, 1895.

MycoBank no.: 16241

= Aplopsora Mains, Am. J. Bot. 8, 442. 1921.

= Ceraceopsora Kakish., T. Sato & S. Sato, Mycologia 76, 969. 1984.

Typification: Ochropsora ariae (Fuckel) Ramsb., Trans. Br. Mycol. Soc. 4, 337. 1914.

Spermogonia subcuticular, conical, hemispherical or discoid with a more or less flat hymenium. Aecia subepidermal, Aecidium-type, and surrounded by a well- or weakly developed peridium. Aeciospores produced in basipetal succession from a basal sporogenous cell layer, uniformly verrucose, weakly bizonate with moderate verrucae above and minute verrucae near the base or conspicuously bizonate with large verrucae or refractive granules on the upper half. Uredinia subepidermal in origin, erumpent, Malupa-type, and surrounded by paraphyses, excepting one species (O. panacis: Uredo-type). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, and not to strongly incurved. Urediniospores singly produced on a short pedicel from a basal sporogenous cell, echinulate, and germ pores either distributed on equatorial zone or scattered over the wall. Telia subepidermal in origin and remaining covered by the host epidermis until germination of teliospores and production of basidia. Teliospores arising from a basal sporogenous cell, one-celled, cylindrical, thin-walled, laterally free, producing a basidium in situ by horizontal septation of a teliospore without significant morphological changes (internal germination) or by continuous apical elongation (external germination), four-celled, and producing a basidiospore from each of four basidial cells.

Note ― Winter (1884) first mentioned that a teliospore of a fungus (the host not specified) named as Melampsora sorbi (Oudem.) G. Winter developed into a basidium upon maturity by 3 or 4 septations with little morphological change. Because this basidium development was characteristic to this fungus, being only comparable to Coleosporium in the rust fungi with sessile teliospores, and because the uredinium was not Caeoma-type, Dietel (1895) proposed a new combination, O. sorbi (Oudem.) Dietel, synonymizing M. sorbi (Oudem.) G. Winter under a newly proposed genus Ochropsora Dietel. Ramsbottom (1914) briefly reviewed the nomenclature of this fungus and proposed O. ariae (Fuckel) Ramsb. to replace O. sorbi as the correct name of this fungus. The reason was that M. ariae Fuckel (1870) was published earlier than was Caeoma sorbi Oudem. (Oudemans, 1872). This proposal did not settle the typification of the genus. Ochropsora sorbi (G. Winter) Dietel was considered to be the proper citation of the type species as accepted by Cummins and Hiratsuka (2003), while O. sorbi (Oudem.) Dietel was accepted by Gäumann (1959). In a life cycle study, a fungus on Sorbus aria (L.) Crantz, originally named as Melampsora ariae Fuckel (Fuckel, 1870, cited from Ramsbottom, 1914), was found conspecific with O. sorbi. Ramsbottom’s (1914) nomenclatural proposal is, therefore, most reasonable as accepted by Wilson and Henderson (1966) and Cummins and Hiratsuka (1983).

Dietel (1923) acknowledged the similarity between Ochropsora and Aplopsora in the characteristically paraphysate uredinium and sessile, one-celled, and thin-walled teliospore and assumed the evolutionary derivation of Ochropsora and Aplopsora from a most recent common ancestor. When describing A. lonicerae Tranzschel (1938), he also pointed out the morphological resemblance of A. lonicerae and A. nyssae to Ochropsora, only differing in the mode of basidium development. The taxonomic separation between Ochropsora and Aplopsora is based only on the mode of teliospore production and basidium development in the type species of the two genera, i.e., “internal” development in O. ariae (Fuckel) Ramsb. (the type of Ochropsora) vs. “external” in A. nyssae Mains (the type species of Aplopsora) (Cummins & Hiratsuka, 1983, 2003; Ono, 2006). This taxonomic distinction was earlier questioned by Ono and Hennen (1983) and Ono (2006). In this study, the genera Ochropsora and Aplopsora were not unequivocally circumscribed and separated from each other, although their species were clearly distinguished by morphology, strict host restriction of the spermogonial and aecial stages on Anemone (Ranunculaceae) or Corydalis and Dicentra (Papaveraceae) (with five unresolved species), heteroecious life cycle (with five unresolved species), and geographic distribution.

A close phylogenetic relationship between the two genera was shown by Aime and McTaggart (2021), in which O. ariae (the type species of Ochropsora) and A. nyssae (the type species of Aplopsora) constituted a monophyletic group, which group was then referred to as a new family Ochropsoraceae. This monophyletic group was further explored by additional sampling in a molecular phylogenetic study (Ebinghaus et al., 2023). The analysis with samples of O. ariae (two samples), O. nambuana (Henn.) Dietel (two samples), O. staphyleae Y. Ono, Chatasiri & E. Tanaka (two samples), and A. nyssae (one sample) recovered a more robust monophyletic group (Ebinghaus et al., 2023). Aplopsora nyssae was nested in the clade of Ochropsora. The result of this molecular phylogenetic analysis supports the delimitation of Ochropsora that includes Aplopsora. Taking all data from the studies on morphology, host preference, life cycle, and molecular phylogeny into consideration, a taxonomic revision of Ochropsora is proposed with Aplopsora being synonymized under Ochropsora.

Keys to species of Ochropsora are supplied in Supplementary Keys.

Ochropsora ariae (Fuckel) Ramsb., Trans. Br. Mycol. Soc. 4, 337. 1914. Fig. 1

MycoBank no.: 119894.

≡ Melampsora ariae Fuckel, Jahrb. nassau. Ver. Naturk. 23-24, 45. 1870.

= Ochropsora pallida (Rostr.) Lind, Danish Fungi (Copenhagen), 286. 1913.

　≡ Melampsora pallida Rostr., Tidsskrift for Skovbrug 2, 153. 1877.

　≡ Melampsora pallida f. pyri-sylvestris Rostr., Tidsskrift for Skovbrug 2, 153. 1877.

　≡ Melampsoridium pallidum (Rostr.) Rostr. Plantepatologi, 301. 1902.

= Ochropsora sorbi (Oudem.) Dietel, Ber. Deutsch. Bot. Ges. 13, 401. 1895.

　≡ Caeoma sorbi Oudem., Fungi Europaei exsiccati Cent. 15: no. 1490. 1871.

　≡ Melampsora sorbi (Oudem.) G. Winter, Rabenh. Krypt. Fl. 2nd ed. (Leipzig). 1, 241. 1881.

　≡ Coleosporium sorbi (Oudem.) Lagerh., Ured. Herb. El. Fries, 95. 1895.

= Ochropsora anemones (Pers. ex F.J. Gmel.) Ferd. & C. A. Jørg., Skovtraeemes Sygdomme 1, 253. 1938.

　≡ Aecidium anemones Pers. ex F.J. Gmel., Syst. Nat. 13th ed. 2, 1473. 1792.

= Aecidium leucospermum DC., in Lamark & de Candolle, Fl. franç. 2, 239. 1805; 6, 90. 1815.

　≡ Caeoma leucospermum (DC.) Schltdl., Fl. Berol. 2 ed (Berlin), Cryptogamia, 116. 1824.

= Uredo ariae Schleich., Cat. Pl. Helv. 4th edn., no. 1821, 1821. nomen nudum.

Fig. 1 - Ochropsora ariae. A-C on Sorbus aria (holotype of Melampsora ariae Fuckel in B). D, E, H on S. aucuparia (Fischer 21 Sep 1903 in B). F, G on S. aucuparia (Fischer 20 Sep 1904 in B). I on Aruncus dioicus (Mayor 18 Sep 1934 in B). A: Uredinial paraphyses. B Urediniospores. C: Cross section of a telium. The teliospores are oblong-ellipsoid or cylindric, thin-walled, and appressed each other but laterally free. D: Urediniospores focused on the horizontal plane. E: Urediniospores (the same as in D) focused on the upper surface, showing scattered germ pores. F, G: Urediniospores focused on two different surfaces, showing several germ pores scattered over the spore wall. H, I: Cross section of a telium. Teliospores are one-celled, thin-walled, cylindric, and appressed each other but laterally free. Basidia are produced by horizontal septation of the teliospores without substantial morphological changes. Bars: 20 µm.

Typification: GERMANY, on Sorbus aria (L.) Crantz (Rosaceae) (Fuckel Fung. rhen, 2219, holotype of Melampsora ariae Fuckel, in G).

Spermogonia scattered on the adaxial leaf surface, subcuticular, conical or obtuse with a more or less flat hymenium, 100-125 µm wide, and 60-70 µm high. Aecia scattered on the abaxial leaf surface, subepidermal in origin, erumpent, and Aecidium-type with a well-developed peridium. Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose to broadly ellipsoid, weakly polyhedral, and 18-30 × 16-21 µm; wall ca. 1 µm thick, colorless, and verrucose. Uredinia scattered or loosely to densely grouped on the abaxial leaf surface, subepidermal in origin, Malupa-type, erumpent, and surrounded by basally united paraphyses. Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, weakly to moderately incurved, and 27-60(-80) × 9-21 µm (Fig. 1A); wall 2-6 µm thick. Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, or obovoid, and 19-30 × 16-25 µm (Fig. 1B, D); wall 1-1.5 µm thick, colorless, and completely echinulate with 6-8(-10) germ pores scattered on the wall (Fig. 1E-G). Telia loosely or densely grouped on the abaxial leaf surface, subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores produced from a basal sporogenous cell, one-celled, thin-walled, laterally free, oblong to cylindrical, and 27-56(-70) × 9-17 µm (Fig. 1C). Basidia four-celled and developed from teliospores without significant morphological change (Fig. 1H, I). Basidiospores narrowly ellipsoid and 25 × 7-8 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on An. nemorosa L. (Ranunculaceae) in Austria, Belgium, Finland, France, Germany, Latvia, Norway, Poland, Romania, Russia, Sweden, Switzerland, and UK. Uredinial and telial stages on Aru. dioicus (Walter) Fernard (= Aru. vulgaris (Maxim.) Raf., Aru. sylvestris Kostel.) in Germany, Norway, Poland, Slovenia, Sweden, and Switzerland; on Mal. pumila Mill. in Germany; on Mal. sylvestris (L.) Mill. in Denmark; on Py. canadensis (L.) Farw. (= Ame. canadensis (L.) Medik.) in Germany and Norway; on Py. communis L. (= Py. sylvestris (L.) Gray) in Denmark, Poland, Russia, and Switzerland; on S. aria (L.) Crantz in Germany, Switzerland, and UK; on S. aucuparia L. in Austria, Belgium, Denmark, Finland, Germany, the Netherlands, Norway, Poland, Russia, Sweden, Switzerland, and UK; on S. hybrida L. in Norway; and on S. torminalis (L.) Crantz in Germany and Switzerland.

Note ― Description of spermogonial, aecial and basidiospore morphology was adapted from Gäumann (1959) and Wilson and Henderson (1966). The nomenclatural history of this fungus is described in the note for the genus above.

Anemone nemorosa harbors not only O. ariae (the aecial anamorph referred to as Ae. leucospermum), but also T. pruni-spinosae (Pers.) Dietel (aecial anamorph referred to as Ae. punctatum Pers.) in northwestern Europe. The two aecial fungi can be differentiated by the aeciospore color, i.e., colorless in the former fungus vs. pale brownish in the latter. However, they can be erroneously identified without close examinations. Anemone blanda Schott & Kotschy, An. hortensis L. (= An. pavonina Lam.), An. ranumculoides L., An. rivularis Buch.-Ham. ex DC., and An. sylvestris L. were recorded as the spermogonial-aecial host plants (references in Farr DF and Rossman AY. Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Retrieved 24 Jan 2018, from https://nt.ars-grin.gov/fungaldatabases/ and specimen record in MyCoportal. Retrieved 20 Mar 2024 from http://mycoportal.org/portal/collections/list.php). However, no experimental inoculation with aeciospores from these anemones onto the potential host plants has confirmed the life cycle connection.

Tranzschel (1903, 1904) first proved the complete heteroecious life cycle of O. ariae. By artificial inoculations, he successfully connected the spermogonial-aecial stages (identified as Ae. leucospermum) on An. nemorosa to the uredinial-telial stages (O. ariae) on S. aucuparia. Subsequently, the heteroecism of the fungus on Aru. dioicus (as Aru. sylvester), Mal. pumila (= Pyr. malus L.), Py. communis, S. americana L., S. aria, S. aucuparia, S. fennica (Kalm) Fr., and S. torminalis was proven by experimentally inoculating aeciospores from An. nemorosa (Fischer, 1904, 1910; Klebahn, 1907). Sorbus latifolia (Lam.) Pers. did not support the infection and sporulation of this fungus (Klebahn, 1907). Gäumann (1959) listed Ame. asiatica, Aru. dioicus (= Aru. vulgaris), Mal. sylvestris, Padus avium Mill. (= Prunus avium (L.) L.), Pr. padus L., S. hybrida, S. latifolia, and S. intermedia (Ehrh.) Pers. as the uredinial-telial hosts.

The systemic infection and perennial nature of aecial mycelia was first proven by Fischer (1904). Tranzschel (1938) was also aware of the systemic nature of the aecial infection of O. ariae on Anemone rhizomes. Klebahn (1907) inoculated rhizome buds of apparently healthy An. nemorosa with basidiospores of O. ariae (a telial host not specified) in autumn and successfully obtained aecia and aeciospores on the Anemone leaves emerged from the infected rhizomes in the following spring. These observations and artificial inoculations proved that this fungus could persist in the spermogonial-aecial stages for a considerable period without completing its heteroecious life cycle when its uredinial-telial hosts do not co-occur at a habitat.

A uninucleate form exists in the fungus named under Ae. leucospermum (Callen, 1940; Kursanov, 1917; Ono, 2002). Its life cycle is not clear, and the nucleus is assumed to be diploid. This fungus, therefore, might be interpreted as an endocyclic derivative of O. ariae (Ono, 2002). This might explain the failure of aeciospores inoculation to potential uredinial-telial host plants (cf. Callen, 1940; Ramsbottom, 1914). However, Dodge (1929) predicted that the uninucleate aeciospores would result in uninucleate teliospores upon infection on the alternate host.

Ochropsora asari (S. Kaneko, Katum. & Hirats. f.) Y. Ono, comb. nov. Figs. 2, 3

MycoBank no.: 854136.

Fig. 2 - Ochropsora asari on Corydalis lineariloba (IBAR6697). A: Spermogonia and aecia produced on systemically infected, enlarged and distorted leaflets. Spermogonia (tiny pale orange-yellow pustules) are produced on the abaxial leaf surface, but not on the adaxial surface. Aecia are produced on the abaxial leaf surface. B: Cross section of a spermogonium. The spermogonium is subcuticular and dome-shaped or discoid with a flat hymenium. C: Cross section of an aecium (right half). The sorus is Aecidium-type, surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. D: Aeciospores. E: Surface structure of aeciospores (SEM). Wall is uniformly verrucose. Bars: B, C 50 µm; D 10 µm; E 5 µm.

Fig. 3 - Ochropsora asari on Asarum caulenscens. A: Uredinia and telia produced on the abaxial leaf surface (IBAR6359). B: Cross section of a peripherally paraphysate uredinium (Malupa-type, right half) (IBAR6706). The paraphysis is uniformly thin-walled. C: Urediniospores (IBAR6706). D: Equatorial germ pores observed in a lactic-acid-lactophenol treated urediniospore (IBAR6706). E: Cross section of a telium (IBAR7022). Teliospores are produced from a basal sporogenous cell, one-celled, thin-walled. cylindrical, and appressed each other but laterally free. Bars: B-D 10 µm; E 20 µm.

Basionym: Cerotelium asari S. Kaneko, Katum. & Hirats. f., Trans. Mycol. Soc. Japan 24, 433. 1983.

Typification: JAPAN, Shimane, Tsuwano-cho, Nayoshi, on Asarum caulescens Maxim. (Aristolochiaceae), 8 Oct 1972, K. Katumoto (holotype, HH-78461; isotype, YAM-21911).

Spermogonia scattered on the abaxial leaf surface (Fig. 2A), subcuticular, hemispherical or discoid with a flat hymenium, 158-230 µm wide, and 90-130 µm high (Fig. 2B). Aecia scattered on the abaxial leaf surface (Fig. 2A), subepidermal in origin, Aecidium-type, surrounded by well-developed peridium, becoming dome-shaped, erumpent by central aperture, and developed into cup-shaped (Fig. 2A, C). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose, broadly ellipsoid or oblong-ellipsoid, and 22-32 × 18-24 µm (Fig. 2C); wall ca. 1 µm thick, colorless, and uniformly verrucose (Fig. 2D, E). Uredinia loosely to densely grouped on the abaxial leaf surface (Fig. 3A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 3B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical or clavate, not to weakly incurved, and 32-54 × 8-14 µm; wall uniformly ca. 1 µm thick. Urediniospores produced singly on a short pedicel, subglobose, obovoid-ellipsoid or oblong-ellipsoid, and 22-32 × 14-21 µm (Fig. 3C); wall 1-1.5 µm thick, colorless, and uniformly echinulate with 4 germ pores distributed on equatorial zone (Fig. 3D). Telia densely grouped on the abaxial leaf surface (Fig. 3A), subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores produced from a basal sporogenous cell, one-celled, thin-walled, laterally free, broadly oblong, oblong or cylindrical, and 33-54 × 8-14 µm (Fig. 3E). Basidia four-celled and developed from teliospores by apical elongation. Basidiospores obovoid or broadly ellipsoid and 12-17 × 9-12 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on Cory. lineariloba in Japan. Uredinial and telial stages on As. caulescens in Japan.

Note ― This fungus was first classified in Cerotelium because one-celled teliospores appeared to be compact and produced in chains in a sorus (Kaneko et al., 1983). Ono (1995a) showed, however, that cylindrical, laterally free teliospores arose successively from a basal sporogenous cell in the sorus hymenium.

Ochropsora asiatica Y. Ono, sp. nov. Figs. 4, 5, 6

MycoBank no.: 854158.

Fig. 4 - Ochropsora asiatica on Anemone pseudoaltaica. A, B: IBAR7334. C-F: IBAR8496. A: Spermogonia and aecia produced on systemically infected, enlarged and distorted leaflets. Spermogonia are produced exclusively on the adaxial surface. B: Aecia produced on the abaxial surface of the systemically infected leaflets. No spermogonia occur on the abaxial leaf surface. C: Cross section of a spermogonium. The spermogonium is subcuticular and conical with a more or less flat hymenium. D: Cross section of an aecium (Aecidium-type, right half). The sorus is surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. E: Aeciospores. F: Surface structure of aeciospores (SEM). Bars: C, D 50 µm; E 10 µm; F 5 µm.

Fig. 5 - Ochropsora asiatica on Aruncus silvester. A: IBAR7756. B-G: IBAR9678. A: Uredinia produced on the abaxial leaf surface (experimental inoculation). B: Cross section of a uredinium. The sorus is Malupa-type and densely paraphysate at the periphery. C: Paraphyses. The paraphyses arise from basal pseudoparenchymatous mycelia and are cylindrical, weakly incurved near the apex, and basally united. D: Urediniospores focused on the horizontal plane. E: Urediniospores (the same as in D) focused on the upper surface. F, G: Lactic-acid-lactophenol treated urediniospores focused on different planes. Four germ pores are distributed on the equatorial zone. Bars: B, C 20 µm; D-G 10 µm.

Fig. 6 - Ochropsora asiatica. A-C on Aria japonica (IBAR10035). D-G on Aruncus silvester (IBAR6225). A: Uredinia (Malupa-type) produced on the abaxial leaf surface (experimental inoculation). B: Uredinial paraphyses. The paraphyses arise from basal pseudoparenchymatous mycelia and are short cylindrical, thick walled, and weakly incurved near the apex. C: Urediniospores. D: Cross section of a telium. Teliospores are oblong-ellipsoid or cylindric and appressed each other but laterally free. E: Teliospores becoming basidia by apical elongation. F: Four-celled basidia (arrows). G: Basidiospores. Bars: B, D-F 20 µm; C, G 10 µm.

Ochropsora ariae auct., non (Fuckel) Ramsb.

Typification: JAPAN, Tochigi, Nikko, on Aruncus silvester Kostel ex Maxim. (Rosaceae), 21 Sep 1992, Y. Ono (holotype, IBAR6225).

Etymology: After the name of geographic distribution range.

Diagnosis: Several equatorial germ pores in urediniospores, basidium production by apical elongation of teliospores, and distribution in eastern Asia separate this species from most similar northwestern European O. ariae with the same life cycle pattern, host-alternating between Anemone and rosaceous plants.

Spermogonia scattered on the adaxial leaf surface (Fig. 4A, B), subcuticular, conical with a flat hymenium, 104-176 µm wide, and 66-119 µm high (Fig. 4C). Aecia produced densely on the abaxial leaf surface (Fig. 4B), subepidermal in origin, erumpent, Aecidium-type, and cupulate with a well-developed peridium (Fig. 4D). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose to broadly ellipsoid, and 14-22(-27) × 11-18(-21) µm (Fig. 4E); wall uniformly ca. 1 µm thick, colorless, and uniformly verrucose (Fig. 4E, F). Uredinia loosely to densely grouped on the abaxial leaf surface (Figs. 5A, 6A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Figs. 5B, 6B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, not to weakly incurved, and 22-70 × 8-18 µm; wall up to 8 µm thick at sides and up to 15 µm thick apically (Figs. 5C, 6B). Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, oblong-ellipsoid or obovoid, and 18-26 × 13-23 µm (Figs. 5D, 6C); wall uniformly ca.1.5 µm thick, colorless, and minutely echinulate (Fig. 5D, E); germ pores (2-)4-6 germ pores, and equatorial or irregularly distributed on equatorial zone (Fig. 5F, G). Telia loosely or densely grouped on the abaxial leaf surface, subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores produced from a basal sporogenous cell, one-celled, thin-walled, laterally free, broadly oblong, oblong-ellipsoid or cylindrical, and 27-54(-65) × 9-19 µm (Fig. 6D, E). Basidia four-celled and developed from teliospores by apical elongation (Fig. 6F). Basidiospores subglobose, broadly ellipsoid or obovoid, and 11-17(-25) × 7-13 µm (Fig. 6G).

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on An. nikoensis and An. pseudoaltaica in Japan. Uredinial and telial stages on Ame. asiatica, and Ari. japonica (= S. japonica) in Japan; on Aru. sylvester (= Aru. dioicus var. tenuifolius (Nakai ex H. Hara) H. Hara, Aru. dioicus var. kamtschaticus (Maxim.) H. Hara, Aru. dioicus var. vulgaris (Maxim.) H. Hara, Aru. vulgaris var. americanus Hara) in Japan and Russia; on Pr. mume Siebold & Zucc. and Py. lindleyi Rheder in Taiwan; on Py. pyrifolia (Burm. f.) Nakai = Py. serrotina Rehder) in Taiwan and Japan; on Py. pyrifolia var. culta (Makino) Nakai (= Py. montana var. rehderi Nakai; Py. xerophila T.T. Yu) in Taiwan; and on Pyrus sp. in Thailand.

Note ― This fungus is widespread in eastern Asia and had been erroneously identified as O. ariae because of its uredinial-telial host range similar to that of northwestern European O. ariae. Ono (2006) noticed that the eastern Asian fungus formed a four-celled basidium by apical elongation (in the external mode) of a teliospore, which was different from a mode of basidium development (internal mode of development) in northwestern European O. ariae. The difference between eastern Asian and northwestern European fungi was inappropriately interpreted by comparing the former fungus to O. nambuana, O. corni (then A. corni), and O. nyssae (then A. nyssae). It was then interpreted that there would be intermediate forms between the external mode in the eastern Asian fungus and the internal mode in northwestern European fungus in the basidium development. An important point in this discussion was, however, that no definite delimitation of Ochropsora and Aplopsora was possible by the characteristics of teliospore production and basidium (Ono, 2006).

Anemone flaccida and An. nikoensis were listed as the spermogonial-aecial hosts in Japan (Hiratsuka et al., 1992). However, no experimental inoculations had been carried out, before this study, to prove the life cycle connection between the spermogonial-aecial stages on the two Anemone spp. to the uredinial-telial stages on the rosaceous plants listed above. Anemone nikoensis and An. pseudoaltaica serve as the spermogonial-aecial hosts of O. lonicerae as in O. asiatica (see subsection 3.1.). Anemone flaccida was also listed as the spermogonial-aecial host of this fungus. This Anemone species has been proven to be the spermogonial-aecial host of O. nambuana and O. laporteae, but not of O. asiatica (see subsection 3.1.). A record of this species on cultivated pear trees in Thailand (Lohsomboon et al., 1986) is likely an accidental anthropogenic introduction, not native to southeastern Asia.

Ochropsora corni (Y. Ono & Y. Harada) Y. Ono, comb. nov. Figs. 7, 8

MycoBank no.: 854159.

Fig. 7 - Ochropsora corni on Anemone raddeana. A-D: IBAR9481. E-G: IBA8669. A: Rust-infected Anemone plants. B: Spermogonia and aecia produced on systemically infected, enlarged and distorted leaflets. Spermogonia are produced exclusively on the adaxial leaf surface. Aecia are produced on the abaxial leaf surface. C: Cross section of a spermogonium. The spermogonium is subcuticular and conical with a flat hymenium. D: Cross section of an aecium. The sorus is Aecidium-type and surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. E: Aeciospores focused on the horizontal plane. F: Aeciospores (the same as in E) focused on the upper surface. G: Surface structure of aeciospores (SEM). Wall is verrucose, bizonate with lager verrucae or refractive granules of various sizes on the upper half. Bars: C, D 50 µm; E-G 10 µm.

Fig. 8 - Ochropsora corni on Cornus controversa. A, D: IBAR9601, B: IBAR9850. C, E-G: IBAR9505. H: IBAR10322. I: IBAR6686. A: Rust symptom on the adaxial leaf surface. B: Uredinia produced on the abaxial leaf surface. C: Cross section of a peripherally paraphysate uredinium (Malupa-type, right half). D: Uredinial paraphyses. E: Urediniospores focused on the horizontal plane. F: Surface view of urediniospores (the same as in E). G: Scattered germ pores observed on lactic-acid-lactophenol treated urediniospores. H: Cross section of a telium. Teliospores are one-celled, thin-walled, oblong, and appressed each other but laterally free. I: Basidia developed by continuous apical elongation of the teliospores. Bars: C, D, H 20 µm; E-G, I 10 µm.

Basionym: Aplopsora corni Y. Ono & Y. Harada, Mycoscience 35, 181. 1994.

Typification: JAPAN, Hokkaido, Hidaka, Shizunai-cho, Experimental farm of Hokkaido University, on Cornus controversa Hemsl. ex Prain (Cornaceae), 26 Sep 1991, Y. Harada (holotype, IBAR6686).

Spermogonia scattered on the adaxial leaf surface (Fig. 7A, B), subcuticular, conical with a flat hymenium, 129-168 µm wide, and 70-155 µm high (Fig. 7C). Aecia scattered on the abaxial leaf surface (Fig. 7B), subepidermal in origin, erumpent, Aecidium-type, and surrounded by a well-developed peridium (Fig. 7D). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose to broadly ellipsoid, and 20-27 × 16-21 µm (Fig. 7E); wall 1-1.5 µm thick, colorless, verrucose, bizonate with lager verrucae or refractive granules of various sizes on the upper half (Fig. 7F, G). Uredinia scattered or loosely to densely grouped on the abaxial leaf surface (Fig. 8A, B), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 8C). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, not to weakly incurved, and 42-60 × 8-16 µm; wall uniformly 2-3 µm thick (Fig. 8D). Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, oblong-ellipsoid or obovoid, and 22-33 × 18-28 µm (Fig. 8E); wall 1-1.5 µm thick, colorless, and completely echinulate (Fig. 8F) with 6-8 faint germ pores scattered on the wall (Fig. 8F, G). Telia loosely or densely grouped on the abaxial leaf surface, subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses (Fig. 8H). Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, laterally free, broadly oblong, oblong-ellipsoid or cylindrical, and 43-68 × 15-24 µm. Basidia four-celled and developed from teliospores by apical elongation (Fig. 8I). Basidiospores obovoid or obovoid-ellipsoid, and 19-24 × 16-20 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ―Spermogonial-aecial stages on An. raddeana in Japan. Uredinial-telial stages on Corn. controversa in Japan.

Note ― Aeciospores of this fungus are unique in having bizonate verrucose wall with lager verrucae or refractive granules on the upper half. This aeciospore surface structure is also observed in Tranzschelia arthurii distributed in North America (Lopez-Franco & Hennen, 1990) and T. asiatica in East Asia (Ono, 1994). Maier et al. (2003) showed that a clade of T. fusca, T. pruni-spinosae, and T. discolor was sister to a clade of O. ariae in the neighbor joining analysis of LSU rDNA (D1/D2 regions) sequences. Further detailed molecular systematic analysis is awaited to see whether O. corni, T. arthurii and T. asiatica are positioned closely in a molecular phylogenetic estimate drawn from a multigene analysis.

Ochropsora cumminsii Y. Ono, sp. nov. Figs. 9, 10

MycoBank no.: 854160.

Fig. 9 - Ochropsora cumminsii on Amphicarpaea bracteata (IBAR10763, holotype). A: A rust-infected Amphicarpaea plant. B: Uredinia and telia produced on the abaxial leaf surface. C: Cross section of a peripherally paraphysate uredinium (Malupa-type). The paraphysis is uniformly thin-walled. D: Urediniospores. E: Scattered germ pores (arrows) on the urediniospore wall (focused on the upper surface). F: Scattered germ pores on the urediniospore wall (focused on the lower surface of the same spore as in E). G: Cross section of a telium. Teliospores are one-celled, thin-walled, oblong or cylindrical, and appressed each other but laterally free. H: A basidium (thick arrow) developed by continuous apical elongation of the teliospore and basidiospores (thin arrows) on collapsed basidia. Bars: C, G 20 µm; D-F, H 10 µm.

Fig. 10 - Possible spermogonial and aecial stages of Ochropsora cumminsii on Dicentra cucullaria (IBAR10013). A: A rust-infected Dicentra plant growing nearby Amphicarpaea plants. B: Spermogonia and aecia produced on systemically infected leaflets. Spermogonia are produced on the abaxial surface, but most commonly at the leaflet edge (arrows). Aecia are produced on the abaxial leaf surface. This rusted Dicentra plant was associated with Amphicarpaea bracteata in close proximity. C: Cross section of a spermogonium. The spermogonium is discoid and subcuticular with a flat hymenium. D: Cross section of an aecium (left half). The sorus is surrounded by a peridium. Aeciospores are produced in basipetal succession. E: Surface view of the aecium. The peridium appears fragile, with individual peridial cells easily separating each other at the edge of sorus (SEM). F: Aeciospores. G: Surface structure of aeciospores (SEM). The wall is verrucose, coarsely above and minutely below. Bars: C-E 50 µm; F 10 µm; G 5 µm.

Cerotelium tanakae auct., non S. Ito (1938).

Typification: U. S. A., Tennessee, Great Smoky Mountains, Meigs Creek, on Amphicarpaea bracteata (L.) Fernald, 16 Oct 2015, Y. Ono (holotype, IBAR10763).

Etymology: In honor of George B. Cummins, the world’s great authority of the rust fungus taxonomy, who first collected this fungus at Brown County State Park, state of Indiana, U. S. A.

Diagnosis: (6-)8-10 germ pores scattered on the urediniospore wall separate this species from most similar O. tanakae on Amphicarpaea edgeworthii var. japonica, distributed in eastern Asia.

Spermogonial and aecial stages probably produced on D. cucullaria. Uredinia loosely to densely grouped on both leaf surfaces (Fig. 9A, B), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 9C). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, not to weakly incurved, and 28-59 × 6-12 µm; wall 1-2 µm thick, colorless, and smooth. Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, oblong-ellipsoid or obovoid, and 17-23 × 15-20 µm (Fig. 9D); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate with (6-)8-10 germ pores scattered on the wall (Fig. 9E, F). Telia hypophyllous, minute, loosely or densely grouped on the abaxial leaf surface, subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses (Fig. 9G). Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, laterally free, broadly oblong, oblong-ellipsoid or cylindrical, and 27-55 × 8-15 µm (Fig. 9G). Basidia four-celled and developed from teliospores by apical elongation (Fig. 9H). Basidiospores subglobose, broadly ellipsoid or obovoid, and 10-12 × 8-10 µm.

Host and geographic distribution (see Supplementary List S2 for detailed information) ― Uredinial and telial stages on Amp. bracteata in U. S. A.

Note ― This fungus was first found at Brown County State Park, Indiana, U. S. A. in 1958 by G. B. Cummins. It has since been collected repeatedly there but not elsewhere (Cummins, 1978) until it was found in Sevier County (Great Smoky Mountains, Meigs Creek Trail), Tennessee, U. S. A. in 2015. This fungus had been referred to be the same as eastern Asian O. tanakae, because of the similarity in morphology and the close host relationships between eastern Asian O. tanakae and eastern North American fungus on Amphicarpaea. However, this study clarified that this fungus is distinct from O. tanakae in urediniospore morphology, i.e., (6-)8-10 scattered germ pores in the former species vs. 6 scattered germ pores in the latter.

Spermogonial and aecial stages are not yet determined for O. cumminsii, although its heteroecious life cycle is suspected. Close associations of D. cucullaria producing spermogonia and aecia with Amp. bracteata were observed at a few sites, Brown County State Park, Indiana, in the 2008 field work (Fig. 10A). Dicentra cucullaria has been proven to be the spermogonial-aecial host for O. dicentrae; however, it could also serve as the spermogonial-aecial host for O. cumminsii. Morphological characteristics of a candidate spermogonial-aecial isolate on D. cucullaria from Brown County State Park are: spermogonia produced on the abaxial leaf surface, almost exclusively at the leaf edge (different from O. dicentrae, Figs. 10B, 11B), subcuticular, disc-shaped with a flat hymenium, 170-228 µm wide, and 46-76 µm high (smaller than O. dicentrae) (Fig. 10C). Aecia scattered on the abaxial leaf surface (Fig. 10B), subepidermal in origin, erumpent, Aecidium-type, and surrounded by a peridium (Fig. 10D, E). The peridium more or less fragile, with individual peridial cells easily separating each other at the edge of sorus (Fig. 10E). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose to broadly ellipsoid, and 13-18 × 11-15 µm (smaller than O. dicentrae) (Fig. 10F); wall uniformly ca. 1 µm thick, colorless, coarsely verrucose above, and minutely below (Fig. 10G).

Ochropsora dicentrae (Trel.) Y. Ono, comb. nov. Figs. 11, 12

MycoBank no.: 854161.

Fig. 11 - Ochropsora dicentrae on Dicentra cucullaria. A, B, E, F: IBAR10018. C, D: IBAR10022. A: An aecium-bearing D. cucullaria plant growing with Laportea canadensis plants. B: Systemically produced Aecidium-type aecia on the abaxial leaf surface. Spermogonia are also produced on the abaxial surface, but more near the leaflet edge (arrows). C: Cross section of a spermogonium. The spermogonium is subcuticular and discoid with a flat hymenium. D: Cross section of an aecium (right half). The sorus is surrounded by a peridium. Aeciospores are produced in basipetal succession. The peridium appears fragile with individual cells easily separating each other at the edge of sorus. E: Aeciospores. F: Surface structure of aeciospores (SEM). The wall is verrucose, coarsely above and minutely below. Bars: C 50 µm; D 20 µm; E 10 µm; F 5 µm.

Fig. 12 - Ochropsora dicentrae on Laportea canadensis. A, B: IBAR0363. C-F: IBAR0977. G, H: IBAR10761. A: Uredinia and telia produced on the abaxial leaf surface. B: Cross section of a peripherally paraphysate uredinium (Malupa-type, Left half). The paraphysis is uniformly thin-walled. C: Uredinial paraphyses. D: Urediniospores focused on the horizontal plane. E: Urediniospores focused on the upper surface. F: Scattered germ pores observed on a lactic-acid-lactophenol treated urediniospore. The spore wall is ruptured by applying gentle pressure to visualize the germ pores. G: Teliospores produced from a basal sporogenous cell. The teliospores are oblong-ellipsoid or cylindric, thin-walled, and laterally free. H: Cross section of a telium. Basidia (thin arrows) are produced by continuous apical elongation of the teliospores (thick arrows). Bars: B 50 µm; D, E-G 10 µm; C, H 20 µm.

Basionym: Aecidium dicentrae Trel., Trans. Wis. Acad. Sci. Art. Lett. 6, 136. 1885.

≡ Cerotelium dicentrae (Trel.) Mains & H.W. Anderson, Amer. J. Bot. 8, 445. 1921.

≡ Aplopsora dicentrae (Trel.) Buriticá & J.F. Hennen, in Buriticá, Rev. Acad. Colomb. Cienc. Exact. Fis. Nat. 22, 333. 1998.

Typification: U. S. A., Wisconsin, Madison, on Dicentra cucullaria (L.) Bernh. (Papaveraceae), May or Jun 1884, Pammel (holotype, ISC-F-0080552).

Spermogonia produced on the abaxial leaf surface, more at the leaf edge (Fig. 11A, B), subcuticular, disc-shaped with a flat hymenium, 181-240 µm wide, and 57-90 µm high (Fig. 11C). Aecia subepidermal in origin, erumpent, Aecidium-type, and surrounded by a peridium (Fig. 11D). The peridium more or less fragile with individual cells easily separating each other at the edge of sorus. Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose to broadly ellipsoid, and 16-22 × 13-18 µm (Fig. 11E); wall uniformly ca. 1 µm thick, colorless, coarsely verrucose above, and minutely below (Fig. 11F). Uredinia minute, loosely to densely grouped on the abaxial leaf surface (Fig. 12A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 12B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, thin-walled, cylindrical, not to weakly incurved, and 27-49 × 6-14 µm (Fig. 12C). Urediniospores produced singly on a short pedicel, appearing almost sessile, subglobose, broadly ellipsoid or oblong-ellipsoid, and 21-25 × 16-22 µm (Fig. 12D); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate with 8 faint germ pores scattered over the wall (Fig. 12E, F). Telia loosely or densely grouped on the abaxial leaf surface (Fig. 12A), subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, oblong-ellipsoid or cylindrical, laterally free, and 27-52 × 9-17 µm (Fig. 12G). Basidia four-celled and developed from teliospores by apical elongation (Fig. 12H). Basidiospores subglobose or obovoid, and 12-15 × 9-14 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on D. cucullaria in Canada and U. S. A. Uredinial and telial stages La. canadensis in U. S. A.

Note ― As to the specimens, on which the species was described and named, Trelease (1885) mentioned only “Madison” and “collected by Mr. Pammel in May 1884.” The specimen has been deposited in the Ada Hayden Herbarium, Iowa State University, ISC-F-0080552, with the collection date as Jun 1884. Three other specimens collected by Trelease in Wisconsin have been deposited in the New York Botanical Garden (NY61105 & 611051 with collection date as 30 May 1885 and NY611052 with no collection date).

The life cycle connection between Ae. dicentrae on D. cucullaria and the uredinial-telial stages on La. canadensis was proven by inoculating aeciospores from the former plant to the latter, resulting in uredinial production (Mains, 1921). The fungus was named as C. dicentrae because the telia appeared to be composed of one-celled, thin-walled, sessile teliospores in one- to three-layers. However, the teliospores of this fungus were found to be cylindrical, laterally free, and aligned in a single layer on a sorus hymenium and, thus, this fungus was re-classified as A. dicentrae (Buriticá, 1998). Telia composed of one-celled, cylindrical teliospores aligned in a single layer are easily misunderstood as if they are composed of one-celled teliospores produced in basipetal succession when the thin-sections for microscopic observations were made obliquely. This was the case in the original description of O. asari (= C. asari) as shown above.

Ochropsora ehimensis Y. Ono, sp. nov. Figs. 13, 14

MycoBank no.: 854162.

Fig. 13 - Ochropsora ehimensis on Amphicarpaea edgeworthii var. japonica (IBAR7768, holotype). A: Rust-infected Amphicarpaea leaves. B: Uredinia and telia produced on the abaxial leaf surface. C: Cross section of a uredinium (Malupa-type). The sorus is densely surrounded by basally united paraphyses. D: Paraphyses. E: Urediniospores focused on the horizontal plane. F: Urediniospore focused on the upper surface. G, H: Lactic-acid-lactophenol treated urediniospores focused on different planes to show scattered germ pores. Bars: C, D 20 µm; E-H 10 µm.

Fig. 14 - Ochropsora ehimensis on Amphicarpaea edgeworthii var. japonica (IBAR7768, holotype). A: Cross section of a telium. Teliospores are produced from a basal sporogenous cell. The teliospores are oblong-ellipsoid or cylindric, thin-walled and laterally free. B: A basidium developed by apical elongation of the teliospore. C: Basidiospores (thin arrows) and subtending collapsed teliospores (thick arrows). Intact teliospores are seen below the collapsed spores. Bars: A, C 20 µm; B 10 µm.

Typification: JAPAN, Ehime Pref., Kita-gun, Hijikawa-cho, on Amphicarpaea edgeworthii var. japonica Oliver (Fabaceae), 3 Oct 1996. Y. Ono (holotype, IBAR7768).

Etymology: After the prefecture name of Ehime where the fungus was discovered.

Diagnosis: Apically thick-walled uredinial paraphyses and urediniospores with 10-12 germ pores scattered on the spore wall separate this species from most closely related O. cumminsii on Amphicarpaea bracteata, distributed in eastern North America, and O. tanakae on Amphicarpaea edgeworthii var. japonica, distributed in eastern Asia.

Uredinia minute, loosely to densely grouped on both leaf surfaces, more on the abaxial surface (Fig. 13A, B), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 13C). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, not to weakly incurved, and 32-50 × 7-14 µm; wall 2-3 µm thick at sides and up to 5 µm thick apically, colorless, and smooth (Fig. 13D). Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, oblong-ellipsoid or obovoid, and 19-29 × 15-18 µm (Fig. 13E); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate with 10-12 faint germ pores scattered on the wall (Fig. 13F-H). Telia produced on the abaxial leaf surface, minute, loosely or densely grouped on the abaxial leaf surface (Fig. 13B), subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores produced from a basal sporogenous cell, one-celled, thin-walled, laterally free, broadly oblong, oblong-ellipsoid or cylindrical, and 33-50 × 8-14 µm (Fig. 14A). Basidia four-celled and developed from teliospores by apical elongation (Fig. 14B, C). Basidiospores subglobose or obovoid and 11-15 × 8-11 µm (Fig. 14C).

Host and geographic distribution ― Known only from the type host and locality.

Note ― Ochropsora ehimensis is most closely related, in morphology and the uredinial-telial host preference, to O. tanakae occurring on Amp. edgeworthii var. japonica and distributed in Hokkaido and Russian Far East. This species likely host-alternates to Corydalis plants other than Cory. fumariifolia subsp. azurea, which is not distributed in the geographic region where the Ehime sample was collected.

Ochropsora kraunhiae (Dietel) Dietel, in Engl. Bot. Jahrb. 37, 106. 1906. Figs. 15, 16

MycoBank no.: 580427.

≡ Phakopsora kraunhiae Dietel, Hedwigia 41, 178. 1902.

≡ Neophysopella kraunhiae (Dietel) Aime & McTaggart, Fungal Syst. Evol. 7, 40. 2020.

　= Aecidium corydalinum Syd. & P. Syd., Monogr. Uredin. 4, 235. 1923.

Fig. 15 - Ochropsora kraunhiae on Corydalis incisa. A, B: IBAR10039. C-E: IBAR7577. F: IBAR4796. A: Spermogonia and aecia produced on systemically infected, enlarged and distorted leaflets. B: Aecidium-type aecia densely produced on the abaxial surface of systemically infected leaflets. C: Cross section of a spermogonium. The spermogonium is subcuticular and discoid with a flat hymenium. D: Cross section of an aecium. The sorus is surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. E: Aeciospores. F: Surface structure of aeciospores (SEM). Verrucae are larger above and smaller near the base. Bars: C, D 50 µm; E 10 µm; F 5 µm.

Fig. 16 - Ochropsora kraunhiae on Wisteria floribunda. A: IBAR9901. B, D, G: IBAR10166. C: IBAR11677. E, F: IBAR7765. A: Uredinia and telia produced on the abaxial leaf surface. The sori are minute and often densely cover entire leaf surface. B: Cross section of a uredinium. The sori are Malupa-type and densely surrounded by basally united paraphyses. C: Paraphyses. D: Urediniospores. E: A lactic-acid-lactophenol treated urediniospore. Germ pores (arrows) are distributed on the equatorial zone. F: Cross section of a telium. Teliospores are oblong-ellipsoid or cylindric and appressed each other but laterally free. G: Collapsed teliospores (thick arrows) and basidiospores produced on basidia (thin arrows). Bars: B 50 µm; C-E 10 µm; F, G 20 µm.

Typification: JAPAN, Tokyo, on Wisteria floribunda (Willd.) DC. (Fabaceae), 11 Oct 1900, T. Nishida (holotype in B).

Spermogonia scattered on the abaxial leaf surface (Fig. 15A, B), subcuticular, disc-shaped with a flat hymenium, 140-211(-300) µm wide, and 37-73 µm high (Fig. 15C). Aecia densely produced on the abaxial leaf surface, subepidermal in origin, erumpent, Aecidium-type, and surrounded by a well-developed peridium (Fig. 15B, D). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose, broadly ellipsoid or oblong-ellipsoid, and (14-)16-25(-28) × 12-19(-23) µm (Fig. 15E); wall uniformly ca. 1 µm thick, colorless, coarsely verrucose above, and minutely near the base (Fig. 15F). Uredinia minute, loosely to densely grouped on the abaxial leaf surface or covering entire abaxial leaf surface (Fig. 16A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 16B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, short cylindrical, not to weakly incurved, thin-walled, and 20-35 × 6-13 µm (Fig. 16C). Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, oblong-ellipsoid or obovoid, and 15-25(-27) × 11-19(-23) µm (Fig. 16D); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate with 2 germ pores distributed on equatorial zone (Fig. 16E). Telia like uredinia, subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, laterally free, oblong or cylindrical, and 26-42 × 8-18 µm (Fig. 16F). Basidia four-celled and developed from teliospores by apical elongation (Fig. 16G). Basidiospores subglobose, broadly ellipsoid or obovoid, and 9-14 × 6-9 µm (Fig. 16G).

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on Cory. decumbens (Thunb.) Pers., Cory. fumariifolia subsp. azurea (as Cory. ambigua auct, non Cham. & Schlecht.), Cory. incisa, Cory. pallida (Thunb.) Pers. var. pallida, and Cory. pallida var. tenuis Yatabe in Japan. Uredinial and telial stages on W. brachybotrys and W. floribunda in Japan.

Note ― Corydalis decumbens, Cory. fumariifolia subsp. azurea, Cory. pallida var. pallida and Cory. pallida var. tenuis listed by Hiratsuka and Kaneko (1978) as the spermogonial-aecial host plants need to be confirmed by further experimental inoculations. Corydalis incisa is the only host species on which the spermogonial-aecial stages are proven to occur by experimental inoculations (Hiratsuka & Kaneko, 1978). Corydalis fumariifolia subsp. azurea is proven to be the spermogonial-aecial host of O. tanakae (this study). Corydalis decumbens is likely to be the spermogonial-aecial host of O. asari, for which Cory. lineariloba is proven to be the spermogonial-aecial host. Further comprehensive experimental inoculations are needed to clarify the life cycle connection of the spermogonial-aecial stages on the listed Corydalis species because two or more Ochropsora species might share the same host species.

Ochropsora laporteae (Hirats. f.) Y. Ono, comb. nov. Figs. 17, 18

MycoBank no.: 854163.

Fig. 17 - Ochropsora laporteae on Anemone flaccida. A, B: IBAR9845. C-F: IBAR10012. A: Spermogonia and aecia produced on systemically infected, enlarged and distorted leaflets. B: Aecidium-type aecia produced on the abaxial surface of a systemically infected leaf. No spermogonia are produced on the abaxial leaf surface. C: Cross section of a spermogonium. The spermogonium is produced on the abaxial leaf surface, subcuticular, and conical with a flat hymenium. D: Cross section of an aecium (right half). The sorus is surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. E Aeciospores. F: Surface structure of aeciospores (SEM). Bars: C, D 50 µm; E, F 10 µm.

Fig. 18 - Ochropsora laporteae on Laportea bulbifera. A, D-F: IBAR10034. B, C: IBAR8530. G: IBAR8567 (epitype). H: IBAR8869. A: Uredinia and telia produced on the abaxial leaf surface. B: Cross section of a uredinium. The sorus is Malupa-type and densely surrounded by basally united paraphyses. C: Cross section of a uredinium (left half). Cylindric and thin-walled paraphyses are basally united at the periphery of the sorus. D: Urediniospores. E, F: Lactic-acid-lactophenol treated urediniospores focused on different planes. Germ pores are distributed on the equatorial zone. G: Cross section of a telium. Teliospores are oblong-ellipsoid or cylindric and appressed each other but laterally free. H: Basidiospores (thin arrows) produced on collapsed basidia (thick arrows). Bars: B-G 20 µm; H 10 µm.

Basionym: Uredo laporteae Hirats. f., Journ. Jap. Bot. 27, 116. 1952.

Typification: JAPAN, Fukui, Eiheiji, on Laportea bulbifera (Siebold & Zucc.) Wedd. (Urticaceae), 24 Sep 1939, N. Hiratsuka and E. Tobinaga (holotype, HH-57841); JAPAN, Tochigi, Nikko, Yunishigawa, 28 Sep 2000, Y. Ono (epitype, MycoBank no.: 10020540; IBAR-8567).

Spermogonia scattered on the adaxial leaf surface (Fig. 17A, B), subcuticular, conical with a flat hymenium, 131-238 µm wide, and 108-199 µm high (Fig. 17C). Aecia subepidermal in origin, erumpent, Aecidium-type, and surrounded by a well-developed peridium (Fig. 17D). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, broadly ellipsoid, oblong-ellipsoid or obovoid, and 18-27 × 14-21 µm (Fig. 17E); wall uniformly ca. 1 µm thick, colorless, and uniformly verrucose (Fig. 17F). Uredinia minute, loosely to densely grouped on the abaxial leaf surface (Fig. 18A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 18B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical or weakly capitate, not to weakly incurved, and 33-67 × 8-17 µm (Fig. 18C); wall thickness variable, up to 4 µm thick dorsally and apically, and colorless or light brown. Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, oblong-ellipsoid or pyriform, and 24-36 × 14-30 µm (Fig. 18D); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate with 6-8 germ pores more or less equatorial or irregularly distributed on equatorial zone (Fig. 18E, F). Telia minute, loosely or densely grouped on the abaxial leaf surface (Fig. 18A), subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, laterally free, cylindrical, and 41-55 × 10-15 µm (Fig. 18G). Basidia four-celled and developed from teliospores by apical elongation (Fig. 18H). Basidiospores subglobose, broadly ellipsoid or obovoid, and 16-19 × 9-14 µm (Fig. 18H).

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on An. flaccida in Japan. Uredinial and telial stages on La. bulbifera in Japan.

Note ― In eastern North America, O. dicentrae occurs on La. canadensis. This fungus host-alternates to D. cucullaria (Papaveraceae). The spermogonial-aecial host relationships, however, indicate that eastern Asian O. laporteae and eastern North American O. dicentrae are not necessarily in a sister species relationship in their disjunct geographic distribution (see subsection 4.5.).

Ochropsora lonicerae (Tranzschel) Y. Ono, comb. nov. Figs. 19, 20

MycoBank no.: 854164.

Fig. 19 - Ochropsora lonicerae on Anemone nikoensis. A, B: IBAR9473. C-F: IBAR8498. A: Spermogonia and aecia produced on systemically infected and distorted leaflets. Spermogonia are produced strictly on the adaxial leaf surface. B: Aecidium-type aecia produced on the adaxial leaf surface. C: Cross section of a spermogonium. The spermogonium is subcuticular and discoid with a flat hymenium. D: Cross section of an aecium (right half). The sorus is surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. E: Aeciospores. F: Surface structure of aeciospores (SEM). Bars: C 100 µm; D 50 µm; E 20 µm; F 5 µm.

Fig. 20 - Ochropsora lonicerae on Lonicera gracilipes var. glabra. A, C-G: IBAR8297. B: IBAR9851. H, I: IBAR11078. A: Uredinia produced on the abaxial leaf surface. B: Cross section of a uredinium. The sorus is Malupa-type and densely paraphysate at the periphery. C: Paraphyses. D: Urediniospores focused on the horizontal plane. E: Urediniospores (the same as in D) focused on the upper surface. F, G: A lactic-acid-lactophenol treated urediniospore focused on two different surfaces, showing several germ pores arranged on the equatorial zone. H: Cross section of a telium. Teliospores are oblong-ellipsoid or cylindric, thin-walled, and appressed each other but laterally free. I: Cross section of a telium. A basidium (narrow arrow) is produced by apical elongation of the teliospore (collapsed, thick arrow). Bars: B 50 µm; C-E, H, I 20 µm; F, G 10 µm.

Basionym: Aplopsora lonicerae Tranzschel (as [Aplospora] lonicerae), Acta Inst. Bot. Acad. Sci. URSS Ser. II. 4, 339. 1938.

Typification: RUSSIA, Amur Oblast, by Sutar River, on Lonicera maximowiczii (Rupr.) Regel (Caprifoliaceae), 1 Aug 1895, V. Komarov (lectotype, MycoBank no.: 10020541, LE59008; isolectotype, PURF9771 = PUR17387).

Spermogonia scattered on the adaxial leaf surface (Fig. 19A, B), subcuticular, broadly conical with a flat hymenium, 168-232 µm wide, and 87-115 µm high (Fig. 19C). Aecia densely produced on the abaxial leaf surface (Fig. 19B), subepidermal in origin, erumpent, Aecidium-type, and surrounded by a well-developed peridium (Fig. 19A, D). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, broadly ellipsoid, oblong-ellipsoid or obovoid, and 19-28 × 15-24 µm (Fig. 19E); wall uniformly ca. 1 µm thick, colorless, and uniformly verrucose (Fig. 19F). Uredinia minute, loosely to densely grouped on the abaxial leaf surface (Fig. 20A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 20B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, weakly to strongly incurved, and 26-79 × 9-18 µm (Fig. 20C); wall dorsally and apically thickened up to 8 µm. Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid, oblong-ellipsoid or obovoid, and (21-)26-40 × 16-30 µm (Fig. 20D); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate with (5-)6-8(-10) germ pores more or less equatorial or irregularly distributed on equatorial zone (Fig. 20E-G). Telia minute, loosely or densely grouped on the abaxial leaf surface, subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, laterally free, broadly oblong, oblong-ellipsoid or cylindrical, and 27-49 × 11-20 µm (Fig. 20H). Basidia four-celled, developed from teliospores by apical elongation (Fig. 20I). Basidiospores broadly ellipsoid or obovoid-ellipsoid, and 16-19 × 12-16 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on An. nikoensis and An. pseudoaltaica in Japan. Uredinial and telial stages on Lo. caerulea L. in Russia and China; on Lo. edulis Turcz. ex Freyn in China; on Lo. gracilipes var. glabra in Japan; on Lo. maximowiczii in Russia and China; and on Lo. strophiophora Franch. in Japan.

Note ― When describing A. lonicerae, Tranzschel (1938) pointed out the morphological resemblance of A. lonicerae and A. nyssae to Ochropsora, only differing in the mode of basidium development, and also to C. dicentrae, noticing the presence of one-celled teliospores in the sorus. He was well aware of systemic nature of the aecial infection of O. ariae on Anemone (Ranunculaceae) and C. dicentrae on Dicentra (Papaveraceae). He also knew unconnected aecial fungi of similar infection habit distributed in the Russian Far East, i.e., Ae. semiaquilegiae Dietel on Semiaquilegia adoxoides (DC.) Makino and Ae. corydalinum Syd. & P. Syd. on Cory. incisa. Thus, he assumed that A. lonicerae would host-alternate to plants belonging to either Ranunculaceae or Papaveraceae. His assumption was proven in this study. It has also been experimentally proven that Ae. semiaquilegiae is the spermogonial-aecial stages of Leucotelium pruni-persicae (Hori) Tranzschel (Hiratsuka, 1952) and Ae. corydalinum is the spermogonial-aecial stages of O. kraunhiae (Hiratsuka & Kaneko, 1978).

Ochropsora nambuana (Henn.) Dietel, Ann. Mycol. 6, 228. 1908. Figs. 21, 22

MycoBank no.: 227184.

≡ Coleosporium nanbuanum Henn., Hedwigia 40 (Beibl.), (25). 1901.

= Ceraceopsora elaeagni Kakish., T. Sato & S. Sato, Mycologia 76, 969. 1984.

Fig. 21 - Ochropsora nambuana on Anemone flaccida. A, B: IBAR9497. C-E: IBAR6701. F: IBAR9820. A: Spermogonia and aecia produced on systemically infected, distorted, and etiolated leaflets. B: Spermogonia and Aecidium-type aecia produced on the abaxial surface of a systemically infected leaf. C: Cross section of a spermogonium. The spermogonium is subcuticular and conical or dome-shaped with a flat hymenium. D: Cross section of an aecium (left half). The sorus is surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. E: Aeciospores. F: Surface structure of aeciospores (SEM). Bars: C, D 50 µm; E 10 µm; F 5 µm.

Fig. 22 - Ochropsora nambuana on Elaeagnus multiflora. A: IBAR7684. B, D, E-G: IBAR9544. C: IBAR7340. H, I: IBAR7683. A: Uredinia produced on the abaxial leaf surface (experimental inoculation). B: Cross section of a uredinium (Left half). The sorus is Malupa-type and densely surrounded by paraphyses. C: Thin-walled, basally united paraphyses. D: Urediniospores focused on the horizontal plane. E: Urediniospores (the same as in D) focused on the upper surface. F, G: Lactic-acid-lactophenol treated urediniospores focused on different planes. Faint germ pores are distributed on the equatorial zone. H: Cross section of a telium. Teliospores are cylindric and laterally free. I: A four-celled basidium (thin arrow) produced by apical elongation of the teliospore (thick arrow). Bars: B, D, E, H , I 20 µm; C, F, G 10 µm.

Typification: JAPAN, Tokyo, Nishigahara, on Elaeagnus umbellata Thunb. (Elaeagnaceae), 14 Oct 1899, N. Nambu 118 (holotype in G, isotype in SAPA).

Spermogonia scattered on both leaf surfaces (Fig. 21A, B), subcuticular, conical with a flat hymenium, 124-200 µm wide, and 70-156 µm high (Fig. 21C). Aecia densely scattered mostly on the abaxial leaf surface (Fig. 21B), subepidermal in origin, erumpent, Aecidium-type, and surrounded by a well-developed peridium (Fig. 21B, D). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose to broadly ellipsoid, and 13-24 × 12-20 µm (Fig. 21E); wall uniformly ca. 1 µm thick, colorless, and uniformly verrucose (Fig. 21F). Uredinia minute, loosely to densely grouped on the abaxial leaf surface, or covering the entire abaxial leaf surface (Fig. 22A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 22B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, thin-walled, cylindrical, not to weakly incurved, and 27-66 × 5-13 µm; wall thin, colorless, and smooth (Fig. 22C). Urediniospores produced singly on a short pedicel, ellipsoid or obovoid, and 20-31 × 16-22 µm (Fig. 22D); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate (Fig. 22E) with 3 or 4 germ pores more or less equatorial or irregularly distributed on equatorial zone (Fig. 22F, G). Telia like uredinia, but not surrounded by paraphyses. Teliospores one-celled, thin-walled, laterally free, oblong or cylindrical, and 46-73 × 11-19 µm (Fig. 22H). Basidia four-celled and developed from teliospores by apical elongation (Fig. 22I). Basidiospores subglobose, broadly ellipsoid or obovoid, and 14-19 × 11-15 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on An. flaccida in Japan. Uredinial and telial stages on E. macrophylla, E. multiflora and E. umbellata in Japan.

Note ― Hennings (1901) first classified this species in Coleosporium even though he noticed a filiform basidium (up to 70 µm long) arising from a teliospore (30-60 µm long). He did not examine the mode of teliospore development. Dietel (1908) reclassified this species in Ochropsora because, unlike Coleosporium species, the urediniospores of this species were formed individually on a pedicel but did not mention the mode of teliospore and basidium development. Microscopic examination of the type specimens of O. nambuana (N. Nambu 118 in B and SAPA) revealed that several teliospores arose from a laterally free sporogenous cell in the sorus hymenium and that the basidium developed from a teliospore by apical elongation (Ono, 2006: Figs. 15, 16).

A fungus host-alternating between An. flaccida and E. umbellata was proposed as a new species in a new genus Ceraceopsora, Ce. elaeagni (Kakishima et al., 1984; Kakishima & Sato, 1984). Host relationships and developmental morphology of teliospores and basidia in the type specimens of Ce. elaeagni completely agreed with those of O. nambuana and, thus, the former species was concluded to be conspecific with the latter (Ono, 2006).

Ochropsora nyssae (Ellis & Tracy) Y. Ono, comb. nov. Fig. 23

MycoBank no.: 854165.

Fig. 23 - Ochropsora nyssae on Nyssa aquatica. A, B, E: PUR3200 (isotype); on Nyssa sp. C, D: IBAR9926; F: PUR66441. A: Uredinia and telia produced on the abaxial leaf surface. B: Cross section of a uredinium. The sorus is Malupa-type and densely paraphysate at the periphery. The paraphyses are basally united. C: Urediniospores focused on the horizontal plane. D: Urediniospores (the same as in C) focused on the upper surface. Germ pores are not apparent. E: Cross section of a telium. The teliospores are oblong-ellipsoid or cylindric, thin-walled, and appressed each other but laterally free. F: Basidia (thin arrows) produced by apical elongation of teliospores (thick arrows). Bars: 20 µm.

Basionym: Uredo nyssae Ellis & Tracy [as ‘nysseae’], J. Mycol. 6, 77. 1890.

≡ Aplopsora nyssae Mains, Amer. J. Bot. 8, 442. 1921.

≡ Physopella nyssae (Ellis & Tracy) Buriticá & J.F. Hennen, Rev. Acad. Colom. Cienc 19, 57. 1994.

Typification: U. S. A., Mississippi, Jackson, on Nyssa aquatica L. (originally reported as N. capitata; corrected by E. B. Mains) (Cornaceae), 12 Nov 1888, S. M. Tracy 1200 (holotype in NY, isotype in PUR).

Spermogonial and aecial stages unknown. Uredinia scattered or loosely to densely grouped on the abaxial leaf surface (Fig. 23A), subepidermal in origin, erumpent, Malupa-type, and surrounded by basally united paraphyses (Fig. 23B). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, weakly to strongly incurved, and (16-)19-38 × 5-13 µm; wall dorsally and apically thickened up to 8 µm (Fig. 23B). Urediniospores produced singly on a short pedicel, broadly ellipsoid, oblong-ellipsoid or obovoid, and 16-29 × 12-19 µm (Fig. 23C); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate; no germ pore observable (Fig. 23C, D). Telia minute, loosely or densely grouped on the abaxial leaf surface (Fig. 23A), subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, laterally free, oblong-ellipsoid or cylindrical, and 19-40 × 7-17 µm (Fig. 23E). Basidia four-celled and developed from teliospores by apical elongation (Fig. 23F). Basidiospores subglobose or obovoid, and 9-17 × 8-13 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Uredinial and telial stages on Ca. acuminata, U. S. A. and on Nyssa aquatica and N. sylvatica in U. S. A.

Note ― Mains (1921) considered that this fungus was heteroecious in the life cycle because the teliospores produced basidiospores without a resting period and because no spermogonial and aecia stages were found on the uredinial-telial host plant. He compared this fungus with Melampsora, Melampsoridium and Chnoopsora (now synonymized under Melampsora), whose species produced one-celled, cylindrical teliospores in a single layer in the sorus, and considered that the fungus was most closely related to Chnoopsora. Thus, he assumed that this fungus would have subcuticular spermogonia and Caeoma-type aecia on some conifer. Ochropsora nyssae occurs on Cornaceae trees in North America and could be comparable to O. corni also on a Cornaceae tree in eastern Asia. Although dimensions are different, uredinial and telial characteristics are similar between the two species. It is unknown whether these two species are a vacariant species pair, being disjunct between eastern Asia and eastern North America as are Tertiary relict floras (see subsection 4.5.). It is, however, likely that these two species are closely related and that O. nyssae would have spermogonial-aecial host(s) either in Papaveraceae or Ranunculaceae. Considering overlapped geographic distribution with Nyssa spp. in eastern North America (e.g., Perry et al., 2022; Spira, 2011; Steyermark, 1963; Wunderlin & Hansen, 2011), An. caroliniana Walter (Ranunculaceae) or its close allies would likely be the spermogonial-aecial host.

Ochropsora panacis (Syd. & P. Syd.) Y. Ono, comb. nov. Figs. 24, 25

MycoBank no.: 854166.

Fig. 24 - Ochropsora panacis on Panax pseudogingseng. A-D, G, H: holotype of Uredo panacis in B. E, F: isotype of Uredo panacis in S. A: Uredinia and telia produced on the abaxial leaf surface. B-D: A urediniospore focused on three different planes. The spore is echinulate with a side smooth portion (arrows). E, F: Urediniospores focused on two different plane. The spore is echinulate with a side smooth portion (arrows). G: Teliospores (asterisks) produced in a uredinium. H: Teliospores arising from a common basal sporogenous cell. Each teliospore is subtended by a sterile cell. Bars: B-F, H 10 µm; G 20 µm.

Fig. 25 - Ochropsora panacis on Panax japonicus (HH51654, holotype of Ochropsora daisenensis). A: A rust-infected leaf. B: Urediniospores focused on the horizontal plane. C: Urediniospores (the same as in B) focused on the upper surface. The wall is echinulate with a smooth portion at side or near the base (arrows). D: Immature teliospores. Each teliospores is subtended by a sterile cell. E: Internally septate mature teliospores (arrows). Bars: 20 µm.

Basionym: Uredo panacis Syd. & P. Syd., Ann. Mycol. 1, 22. 1903.

= Ochropsora daisenensis T. Hirats. & S. Uchida, in Hiratsuka, Scientific Bull. Agric. Home Econ. & Eng. Div., Univ. Ryukyus 7, 216, 1960.

Typification: INDIA, Sikkim, on Panax pseudoginseng Wall. (Araliaceae), probably collected in 1849, J. D. Hooker, f. and T. Thomson (holotype in B designated here; F32650 and F32651 in S, isotypes designated here).

Spermogonial and aecial stages unknown. Uredinia loosely to densely grouped on both leaf surfaces, but more on the abaxial surface (Figs. 24A, 25A), subepidermal in origin, erumpent, Uredo-type, and non-paraphysate. Urediniospores produced singly on a short pedicel, globose to broadly ellipsoid, oblong-ellipsoid or broadly obovoid, and 18-32(-35) × 15-27(-30) µm (Figs. 24B-F, 25B, C); wall uniformly ca.1.5 µm thick, colorless, and echinulate at upper 2/3 and becoming smooth toward pedicel scar, and no germ pore observed (Figs. 24B-F, 25B, C). Telia mixed in uredinial clusters (Fig. 24A). Teliospores one-celled subtended by a sterile cell, a few arising from a basal sporogenous cell, thin-walled, laterally free, broadly oblong-ellipsoid or broadly pyriform, and 38-70(-80) × 18-29 µm (Figs. 24G, 25D). Sterile subtending cells up to 50 µm long (Figs. 24H, 25D, E). Basidia four-celled and developed from teliospores with little morphological change (Fig. 25E). Basidiospores not observed.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Uredinial and telial stages on Pa. pseudoginseng in India and China; on Pa. japonicus C.A. Mey in Japan and China; and on Pa. quinquefolius L. in China.

Note ― Generic placement of this fungus is not conclusive. The non-paraphysate, Uredo-type uredinia, the teliospores subtended by an elongated sterile cell, and replacement of the teliospores by four-celled basidia suggest the taxonomic affinity of this fungus to the genus Achrotelium (Cummins & Hiratsuka, 2003; Ono, 1978). Currently five species (Ono, 1978) or seven species (Cummins & Hiratsuka, 2003) are recognized in Achrotelium. Neither critical biological study nor molecular phylogenetic analyses has been carried out on Achrotelium species since Ono’s (1978) revision. Therefore, this fungus is retained in Ochropsora until its enigmatic biology and precise developmental morphology are elucidated.

The ginseng rust fungus was first described based on a specimen on Pa. pseudoginseng from Sikkim-Himalaya (Sydow & Sydow, 1903). The specimen was collected by J. D. Hooker and T. Thomson during the three-year-long expedition to the Himalayas. No date was recorded on the specimen, but it must have been collected in 1849, only when they were admitted to the region of the Kingdom of Sikkim at that time (O'Brien, 2017). The specimen was divided and each of two parts has been deposited in Berlin (B) and Stockholm (S). As Sydow and Sydow (1903) mentioned, the specimen was old and sori were almost collapsed. However, urediniospores and teliospores intermixed in the sori were recovered by microscopic observations in this study. The observed morphology of urediniospores and teliospores agreed with those described by Hiratsuka (1960) and later by Zhuang and Wei (1990), except for the presence of smooth part in urediniospores and of a sterile cell subtending the teliospore. Exact mode of teliospore development was not determined in this study. However, the sterile cell subtending the teliospore might better be interpretated as equivalent to what first observed in Coleosporium (Kaneko, 1977, 1981). These morphological characteristics were confirmed also in the type of O. daisenensis.

This fungus causes severe leaf rust disease of Pa. pseudoginseng grown as a medicinal herb in Guangxi and Yunnan Provinces, China. It also infects and sporulates on Pa. japonica and Pa. quinquifolius (native of North America) (Zhuang & Wei, 1990). It is likely that this fungus would cause severe leaf rust to all Panax species, including Pa. ginseng, one of the most valuable medicinal herbs.

Ochropsora staphyleae Y. Ono, Chatasiri & E. Tanaka, Mycoscience 61, 63. 2020. Fig. 26

MycoBank no.: 838282.

Fig. 26 - Ochropsora staphyleae on Staphylea bumalda. A: IBAR9910. B, C: IBAR7936. D: IBAR7323. A: Rust-infected leaves. Minute telia often cover the entire adaxial surface. B: Cross section of a telium. Teliospores are cylindric and laterally free. C: A four-celled basidium (thin arrow) produced by apical elongation of the teliospore (collapsed). D: Basidiospores. Bars: B, C 20 µm; D 10 µm.

Typification: JAPAN, Tochigi Pref., Nikko, Yunishigawa, along the Yasugamori-rindo forest path, on Staphylea bumalda DC. (Staphyleaceae), 28 Sep 2000. Y. Ono (holotype, IBAR8587).

Spermogonia and aecia unknown. Uredinia probably not produced. Telia minute, densely produced on the abaxial leaf surface, causing pale green to whitish lesions of various sizes, sometimes covering the entire abaxial leaf surface (Fig. 26A), subepidermal in origin, slightly raised or cushion-shaped, and pale amber, becoming whitish and fluffy due to production of basidia and basidiospores. Teliospores arising from a basal sporogenous cell, one-celled, oblong-ellipsoid or cylindrical, sessile, laterally free, and 28-50 × 10-16 µm (Fig. 26B); wall thin, colorless, and smooth. Basidia produced by continuous apical elongation of teliospores, emerging by rupturing the host epidermis, and four-celled (Fig. 26C). Basidiospores obovoid, broadly ellipsoid or subglobose, and 13-18 × 10-14 µm; wall thin, colorless, and smooth (Fig. 26D).

Host and geographic distribution (see Supplementary List S2 for detailed information) ― on St. bumalda in Japan.

Note ― Five experimental inoculations with aeciospores produced on An. nikoensis and three on An. pseudoaltaica were undertaken during a period between 1996 and 2020 (cf. Ono et al., 2020a). No aeciospore inoculation was successful, and, thus, the complete life cycle of this species remains unknown. However, because the host tree is deciduous and because the fungus teliospores germinate in situ, a heteroecious life cycle is not ruled out.

Ochropsora tanakae (S. Ito) Y. Ono, comb. nov. Figs. 27, 28

MycoBank no.: 854167.

Fig. 27 - Ochropsora tanakae on Corydalis fumariifolia subsp. azurea. A: IBAR10382. B-F: IBAR9829. A: Spermogonia and aecia produced on systemically infected, enlarged and distorted leaflets. B: Spermogonia (reddish brown dots) and Aecidium-type aecia (bright orange pustules) produced strictly on the abaxial surface. C: Cross section of a spermogonium. The spermogonium is discoid and subcuticular with a flat hymenium. D: Cross section of an aecium. The sorus is surrounded by a well-developed peridium. Aeciospores are produced in basipetal succession. E: Aeciospores. F: Surface structure of aeciospores (SEM). Bars: C, D 100 µm; E 10 µm; F 5 µm.

Fig. 28 - Ochropsora tanakae on Amphicarpaea edgeworthii var. japonica. A-G: IBAR9857. H, I: IBAR9750. A: A rust-infected plant. B: Uredinia and telia produced on the abaxial leaf surface. C: Cross section of a uredinium. The sorus is Malupa-type and densely paraphysate at the periphery. D: Paraphyses. E: Urediniospores. F, G: A lactic-acid-lactophenol treated urediniospore focused on two different surfaces, showing several germ pores scattered over the spore wall. H: Cross section of a telium. Teliospores are one-celled, thin-walled, cylindric, and appressed each other but laterally free. I: Basidia (thin arrows) produced by apical elongation of teliospores (thick arrows). Bars: C 50 µm; D-I 10 µm.

Basionym: Cerotelium tanakae S. Ito, in Ito and Homma, Trans. Sapporo Nat. Hist. Soc. 15, 118. 1938.

≡ Aplopsora tanakae (S. Ito) Buriticá & J.F. Hennen, in Buriticá, Rev. Acad. Colomb. Cienc. Exact. Fis. Nat. 22, 332. 1998.

Typification: JAPAN, Hokkaido, Sapporo, Maruyama, on Amphicarpaea edgeworthii var. japonica Oliver (as Falcata commosa var. japonica Makino in the original description) (Fabaceae), 29 Aug 1927, I. Tanaka (holotype in SAPA; isotype HH40631).

Spermogonia scattered on the abaxial leaf surface (Fig. 27A, B), subcuticular, disc-shaped with a flat hymenium, 284-364 µm wide, and 68-92 µm high (Fig. 27C). Aecia densely or loosely scattered on the abaxial leaf surface, subepidermal in origin, erumpent, Aecidium-type, surrounded by a well-developed peridium (Fig. 27B, D). Aeciospores produced in basipetal succession from a basal sporogenous cell layer, subglobose to broadly ellipsoid, and 13-18 × 11-15 µm (Fig. 27D, E); wall uniformly ca. 1 µm thick, colorless, coarsely verrucose above, and minutely near the base (Fig. 27F). Uredinia minute, loosely to densely grouped on the abaxial leaf surface or occasionally on both leaf surfaces (Fig. 28A, B), subepidermal in origin, erumpent, Malupa-type, becoming erumpent, and surrounded by basally united paraphyses (Fig. 28C). Paraphyses arising from a basal pseudoparenchymatous mycelial layer, cylindrical, and not to weakly incurved, and 33-53 × 6-10 µm (Fig. 28D); wall uniformly 1-2 µm thick. Urediniospores produced singly on a short pedicel, subglobose, broadly ellipsoid or obovoid, and 17-27 × 15-21 µm (Fig. 28E); wall uniformly ca.1.5 µm thick, colorless, and completely echinulate; germ pores faint and 6 scattered on the wall (Fig. 28F, G). Telia loosely or densely grouped on the abaxial leaf surface, subepidermal in origin, remaining covered by host epidermis until basidium development, and not surrounded by paraphyses. Teliospores arising from a basal sporogenous cell, one-celled, thin-walled, laterally free, cylindrical, and 23-54 × 7-14 µm (Fig. 28H). Basidia four-celled, developed from teliospores by apical elongation (Fig. 28I). Basidiospores subglobose, broadly ellipsoid or obovoid, and 10-15 × 6-11 µm.

Hosts and geographic distribution (see Supplementary List S2 for detailed information) ― Spermogonial and aecial stages on Cory. fumariifolia subsp. azurea in Japan. Uredinial and telial stages on Amp. edgeworthii var. japonica in Japan and Russia.

Note ― This fungus is widespread in eastern Asia on Amp. edgeworthii var. japonica. Eastern North American O. cumminsii occurs on Amp. bracteata and is similar in uredinial and telial morphology, except for the number of urediniospore germ pores. Considering diversification and migration of Corydalis and Dicentra in the past geological history (see subsection 4.5.), these two species might have diverged by independent host-jump from a hypothetical common ancestor followed by separate speciation in disjunct geological regions.

It has not been a common practice to explicitly express our views of organismic species in individual empirical taxonomic papers of rust (and/or other) fungi. Almost insurmountable disagreements between different species concepts and recognition criteria come from different views or philosophy as to how the separately evolving lineages arise and how they can be appropriately delimited and recognized (e.g., Agapow et al., 2004; de Queiroz, 1998; Harrison, 1998; Hull, 1999; Mayden, 1997). Organisms exhibit a great diversity of biological properties, that we have not yet well understood and accurately evaluated. Different biological properties evolve neither in regular sequence nor tempo among different organisms (de Queiroz, 1998, 2007). Therefore, no single concept and criterion can suffice to recognize species. Nonetheless, explicit, even simple and brief, statement or interpretation as to how species is recognized in each empirical study would be beneficial to make proper evaluation of the species recognition and their classification by different authors, who might have distinct philosophy about species. My view of rust species and methods to delimit them follow the theoretical and practical considerations of the species concept and species recognition by Avise and Wollenberg (1997), de Queiroz (1998, 1999, 2007), Freudenstein et al. (2017), Mayr (1982, 1988), Ono (2000, 2008), and Ono et al. (2020b). Theoretically, species exist as a separately evolving metapopulation lineage (de Queiroz, 1998, 1999, 2007). In practice, species are viewed as the key units in natural biotic diversity, and their phenotypic distinguishability is of fundamental importance (Freudenstein et al., 2017; Mayr, 1982; Ono, 2008). The determination of distinct life cycle with unique host preference in each of individual rust fungi (metapopulations) is considered to fulfil very basis of rust species recognition and permits further comparative morphological, meaningful molecular phylogenetic, and biogeographic analyses of the rust fungi.

In this study, unique macrocyclic heteroecious life cycle was determined for O. asari, O. asiatica, O. corni, O. laporteae, O. lonicerae, O. nambuana, and O. tanakae. The complete life cycle was published for O. ariae (Fischer, 1904, 1910; Klebahn, 1907; Tranzschel,1903, 1904), O. asari (Ono,1995a), O. dicentrae (Mains, 1921), O. kraunhiae (Hiratsuka & Kaneko, 1978), and O. nambuana (Ono, 2006) either prior to or during this long-term study. A complete life cycle is not known in O. cumminsii, O. ehimensis, O. nyssae, O. panacis, and O. staphyleae. Intimate association between the spermogonial-aecial fungus on D. cucullaria, and the uredinial-telial fungus on Amp. bracteata at habitats in state of Indiana, U. S. A., suggests that O. cumminsii likely has a macrocyclic, heteroecious life cycle, its spermogonial and aecial stages occurring on D. cucullaria as in O. dicentrae. Ochropsora staphyleae is inferred to be microcyclic in the life cycle from field observations and experimental inoculations, but its complete life cycle remains inconclusive.

Fifteen species are recognized as distinct by integrating information on morphological characteristics, unique host preference, distinct life cycle pattern, and geographic distribution. All these species are now classified in the genus Ochropsora. Their taxonomic unity is primarily based on the phylogenetic inference from the shared spermogonial-aecial hosts (Ranunculaceae and Papaveraceae) (see subsection 4.4.; Figs. 29, 30) and the similarity in uredinial characteristics and teliospore morphology (see subsection 3.5.). Their generic assignment is also a consequence of the nomenclatural procedure. As mentioned in the note for the delimitation of the genus, recent molecular phylogenetic analyses provided us with important insight into probable close evolutionary unity between Ochropsora and Aplopsora. Aplopsora nyssae, the type species of the genus, was nested in the clade of Ochropsora, in which O. ariae, the type species of the genus was included, in a phylogenetic tree generated from an analysis of nuclear 28S rDNA and 18S rDNA, and mitochondrial cytochrome c oxidase subunit 3 gene markers (Ebinghaus et al., 2023). This molecular phylogenetic study supports the taxonomic view that Aplopsora is congeneric with Ochropsora and the classification of the fifteen species, that were separately classified in Ochropsora, Aplopsora, and Cerotelium p.p., in the newly circumscribed Ochropsora.

Fig. 29 - Life cycle and geographic distribution of Ochropsora species host-alternating to Anemone (Ranunculaceae). Anemone (Ranunculaceae), encircled by purple line, is the spermogonial-aecial host. Reddish orange, bidirectional arrows show host-alternation in each species.

Fig. 30 - Life cycle and geographic distribution of Ochropsora species host-alternating to Corydalis or Dicentra (Papaveraceae). Corydalis or Dicentra (Papaveraceae), encircled by purple line, is the spermogonial-aecial host. Reddish orange, bidirectional arrows show host-alternation in each species. A heteroecious life cycle of O. cumminsii is speculative (see the text).

Ochropsora (previously Ochropsora, Aplopsora, and Cerotelium p.p.) was once classified in a new family Chaconiaceae (Cummins & Hiratsuka, 1983). Cummins and Hiratsuka (1983) included in Chaconiaceae those genera that form one-celled, thin-walled, sessile teliospores, i.e., Chaconia Juel (7 species), Goplana Racib. (10 species), Hemileia Berk. & Broome (50+ species), Olivea Arthur (8 species), Ochropsora (4 species), Aplopsora (6 species), and Ceraceopsora (1 species), together with those that form one-celled, thin-walled, pedicellate teliospores, i.e., Achrotelium Syd. (5 species), Botryorhiza Whetzel & Olive (1 species), and Maravalia Arthur (31 species). Ono and Hennen (1983) and Ono (1984) accepted Chaconiaceae, but did not include Achrotelium, Aplopsora, Botryorhiza, Hemileia, Maravalia, and Ochropsora in this family. The genus Chrysocelis Lagerh. & Dietel (7 species) was included in Chaconiaceae by Ono and Hennen (1983) and Ono (1984). However, it was classified in another new family Mikronegeliaceae by Cummins and Hiratsuka (1983). Achrotelium and Hemileia are now differently classified in Mikronegeliaceae, together with Blastospora Dietel, Elateraecium Thirum., F. Kern & B.V. Patil (= Hiratsukamyces Thirum., F. Kern & B.V. Patil), Mikronegeria Dietel, and Zaghouania Pat. (= Cystopsora E.J. Butler) (Aime & McTaggart, 2021) or in Zaghouaniaceae (Wood & Aime, 2024).

An early molecular phylogenetic analysis with a suprageneric taxonomic perspective based on SSU and LSU ribosomal DNA sequences has shown that the rust species classified in Chaconiaceae, i.e., H. vastatrix Berk. & Broome, Mar. cryptostegiae (Vestergr.) Y. Ono, and Ol. scitula Syd., did not form a monophyletic group (Aime, 2006). Subsequent molecular phylogenetic studies with additional species from chaconiaceous genera, i.e., O. ariae (Maier et al., 2003); Ch. lupini Y. Ono and O. ariae (Wood et al., 2014); Ac. ichnocarpi Syd., H. vastatrix, Hemileia sp., and Mar. cryptostegiae (McTaggart et al., 2016), showed that species formerly classified in Chaconiaceae were diffused in different families. Molecular information to infer the phylogenetic status of Ochropsora was only available for O. ariae, which indicated that Ochropsora was closely related to Tranzschelia and belonged to Uropyxidaceae or more inclusively to Pileolariaceae. However, current knowledge on biological properties and genomic information of Ochropsora and Aplopsora are largely lacking and, therefore, it is difficult to determine their phylogenetic and taxonomic identity as indicated by Ono (2006).

Ono and Hennen (1983) and Ono (1984, 2006) assumed that chaconiaceous rust fungi position near basal to the rust fungus phylogeny. It was also suggested that life cycle studies of species in the chaconiaceous genera would elucidate the process of early life cycle evolution in the Pucciniales (Ono, 2002). These assumptions were not supported by a molecular phylogenetic study (Aime, 2006). Contrarily to the assumptions by Ono and Hennen (1983) and Ono (1984, 2006), Aime and McTaggart (2021) showed that A. nyssae (the type species of Aplopsora) and O. ariae (the type species of Ochropsora) comprise a group, that was referred to as a new family Ochropsoraceae, supporting a claim for the redundancy of polyphyletic Chaconiaceae (Aime, 2006). They provided us with a phylogenetic inference with higher resolution at deeper nodes in the Pucciniales and a currently available most comprehensive higher-rank classification of the order, which could be a good framework for further elaboration of the rust fungus classification at all taxonomic ranks. Because of the broad coverage of the representative genera in the formerly accepted families in the Pucciniales and because of the necessity to sample the type species, wherever possible, their phylogenetic inference on Ochropsoraceae, as in other genera, is based only on the type species with a single sample in each of Aplopsora and Ochropsora. The framework for Ochropsoraceae in the new suborder Raveneliineae provides us with a basis for a more comprehensive taxonomic study of the species in the two genera. More critical analyses and integration of currently available data on their biological properties, i.e., morphology, host preference, life cycle, and geographic distribution, together with broader sampling of Ochropsora for molecular phylogenetic analyses, would bring about a clearer view of biological nature, evolution, and taxonomy of Ochropsora species. Additionally, rigorous exploration for new rust fungi that would have been classified in Ochropsora and its phylogenetic allies would broaden the scope of biological and evolutionary studies of the rust fungi.

In this study, a large proportion (ca. 60%) of experimental inoculations with aeciospores did not result in successful infection and urediniospore production on the potential uredinial-telial host plants. This failure in the experimental inoculations is due to several reasons. The inoculations were possible only when aeciospores were abundantly produced on the Anemone and Corydalis plants, either field-collected from various sites or grown under cultural managements at Ibaraki University campus in Mito. Potential uredinial-telial host plants might not be under a physically and physiologically susceptible phase when the aeciospores were available for the inoculations. Unexpanded juvenile or fully expanded, over-matured leaves were not suitable to aeciospore infection and urediniospore production on the inoculated plants. These phenomena have been empirically observed by repeated inoculations in the same aecial inoculum and uredinial-telial host plant combinations at different time of seasons. The other reason might be that aecial fungi on Anemone and Corydalis plants, that were used in the study, were spermogonial-aecial states of unconnected uredinial-telial fungi of genera other than those under study. Spermogonial-aecial stages produced on An. pseudoaltaica has been connected to uredinial-telial stages of Tranzschelia species on Prunus buergeriana Miq. (Rosaceae) (Supplementary Table S1; Ono, 2006). It is likely that there are some other unconnected uredinial-telial rust fungi, whose spermogonial-aecial stages occur on Anemone and Corydalis plants, in Japan. Despite this unavoidable failure, the life cycle and host preference study brought a clear view on the biological nature of Ochropsora species, which in turn would help pursuing the study on their past evolutionary history and geographical distribution in the Northern Hemisphere.

The geographic distribution of fifteen Ochropsora species herein recognized shows high diversity in eastern Asia while strikingly low diversity in eastern North America and northwestern Europe (Figs. 29, 30). Caution must be taken, however, in considering an uneven distribution pattern of Ochropsora species currently observed in the Northern Hemisphere. It might have resulted from uneven field survey both in geographic ranges and intensity. Ochropsora species produces minute uredinial-telial sori and simple thin-walled teliospores that are cryptic, not typical of rust fungi; namely, no sharp morphological distinction exists between teliospores of rust fungi (Pucciniales) and probasidia of Platygloea (Platygloeales) (Aime et al., 2006; Swann et al., 2001). They might have been easily overlooked or mistaken as non-rust in the field survey. Ochropsora staphyleae represents a typical example (Fig. 26). Even in eastern Asia, exploration of Ochropsora and its allies might not be sufficient enough to fully analyze their diversity, biological nature, evolutionary history, and geographic distribution.

Ochropsora species show strict host preference to either Anemone (Ranunculaceae) or Corydalis and Dicentra (Papaveraceae) in the spermogonial and aecial stages, with a broad taxonomic range of the uredinial and telial host selections, in their heteroecious life cycle (with five unresolved species). Five species (O. asiatica, O. corni, O. laporteae, O. lonicerae, and O. nambuana), host-alternating to Anemone (Ranunculaceae), occur in eastern Asia, one (O. ariae) in northwestern Europe, and none in eastern North America. Three species (O. asari, O. kraunhiae, and O. tanakae), host-alternating to Corydalis (Papaveraceae), occur only in Japan, while one species (O. dicentrae), host-alternating to D. cucullaria (Papaveraceae), and another (O. cumminsii), speculated to host-alternate on the same spermogonial-aecial host species, occur only in eastern North America. All these ranunculaceous or papaveraceous plants represent forest floor perennial herbs with a short foliar growing and flowering period in the spring (“spring ephemerals”). They clonally reproduce (in addition to sexual reproduction) in the spring and persist by rhizomes (Anemone) or by bulbs/bulblets or tubers (Corydalis and Dicentra), excepting primarily biennial Cory. incisa, during the rest of seasons under the closed canopy of cool-temperate deciduous or warm-temperate mixed hardwood forests. All Ochropsora species, for which a complete heteroecious life cycle is clarified, systemically infect rhizomes, tubers or bulbs/bulblets of the spermogonial-aecial hosts and persist in the hosts’ underground organs for a considerable period (see the note for O. ariae). It is unknown how easily and how often the basidiospore infection to the perennial underground organs of the spermogonial-aecial host can be successful in Ochropsora species. It is, however, certain that the heteroecious Ochropsora species could survive for a considerably long period of time only by the spermogonial-aecial stages, even if their uredinial-telial hosts are absent or under unfavorable conditions for the aeciospore infection in some years. This unique trait enables the heteroecious Ochropsora species to safely migrate and effectively expand their distribution range together with their hosts. For them, successful dispersal by short-lived aeciospores and basidiospores is a fortuitous ecological event in completing their life cycle by the host-alternation. The survival of perennial mycelia in the spermogonial-aecial hosts’ underground organs and production of abundant aeciospores in each spring in a considerably long period will certainly increase the probability of successful completion of the heteroecious life cycle. Thus, it in turn secures simultaneous migrations of the Ochropsora fungi together with their spermogonial-aecial and uredinial-telial hosts to new geographic regions even in a long geological time scale.

The successful simultaneous migrations of the heteroecious Ochropsora fungi with their hosts to new geographic regions can be facilitated only if the spermogonial-aecial hosts and the uredinial-telial hosts are in close eco-physiological relationships in each habitat of the distribution range. Plant taxa that serve as the uredinial and telial hosts of Ochropsora species span a broad range of phylogenetic relationships; however, they are either broad-leaved deciduous trees, lianas or forest floor perennial herbs (with rhizomes, tubers or bulbs/bulblets) in cool-temperate deciduous and warm-temperate hardwood forests under mesic conditions (Numata, 1974; Ohwi, 1965; Okitsu, 2003; Spira, 2011; Steyermark, 1963; Wunderlin & Hansen, 2011). Thus, plant taxa that serve as the host of all life cycle stages of Ochropsora in Japan are the member of mixed deciduous forests under mesic temperate climates. The same is true for the eco-geographic associations between D. cucullaria, La. canadensis, and Amp. bracteata in eastern North America (e. g., Perry et al., 2022; Spira, 2011; Steyermark, 1963; Wunderlin & Hansen, 2011).

The rust fungi are biotrophs and ecologically obligate parasites of vascular plants. Their phylogenetic diversity is considered to have been shaped by the co-related speciation between the rust fungi and their host plants (Aime et al., 2018; McTaggart et al., 2016; Roy, 2001; Thines, 2019) through host-jump and host-shift (in sense of Roy, 2001; cf. Giraud et al., 2010; Thines, 2019). Leppik (1953) hypothesized that individual rust lineages with the heteroecious life cycle have diversified and speciated by stepwise switching of their alternate hosts, from ancestral to recently derived taxa (a hologenetic ladder hypothesis). Alternations of two antagonistic evolutionary processes are involved in this hologenetic ladder hypothesis, i.e., biological specialization (Leppik, 1965) and biogenic radiation (Leppik, 1967). In biogenic specialization, a rust fungus jumps to a new host taxon and specializes to explore it, theoretically based on the gene-for-gene type of interactions (Flor, 1956; Leppik, 1965; Thines, 2019). This new host taxon would have served as the primary (spermogonial-aecial) host (in sense of Leppik, 1967). Biological specialization is firmly fixed in the alternation of generation as a regular switching between the two different host taxa (Leppik, 1965). Biogenic radiation is an adaptive dispersion of individual rust fungi from the primary (spermogonial-aecial) host to many different (uredinial-telial) host taxa, which are not phylogenetically closely related to the primary host (Leppik, 1967). These opposite evolutionary tendencies have resulted phylogenetically closely related rust species in a genus to have a high degree of taxonomic variability for the uredinial and telial hosts, while maintaining a close taxonomic proximity in the spermogonial and aecial hosts. These evolutionary scenarios were strongly supported by a rust/host phylogeny reconciliation analysis with a large number of reciprocal rust fungus and host datasets (Aime et al., 2018). Aime et al. (2018) hypothesized that the aecial host is under the strongest selective pressure for conserving host associations, which was interpreted as a function of biological specialization, i.e., the aecial stage is shaping the co-diversification between the rust fungi and their hosts. The spermogonial stage is the gametophytic phase where compatible gametes recombine to initiate the dikaryotic sporophytic phase in the life cycle. The dikaryotic mycelia resulted from fertilization between spermatia and receptive hyphae in the spermogonia likely contain new combinations of alleles and produce genetically variable dikaryotic aeciospores. These aeciospores with new allele combinations could have enhanced capability to infect new uredinial and telial hosts (Aime et al., 2018). Thines (2019) discussed ecological and molecular genetic bases for the speciation events in the rust fungi and other plant pathogens by the host shift. He pointed out an important aspect on the regulation changes in phase-specific transcription factors in the host-alternating rust fungi: these factors can be regulated by a strong separation of gene regulation in monokaryotic gametophytic and dikaryotic sporophytic phases in the life cycle. This genetic basis is likely involved in the host jump/shift in the rust speciation.

The results of this study (Figs. 29, 30) are congruent with the evolutionary scenario described above, i.e., a hypothetical ancestor genetically specializing on the spermogonial-aecial host(s), subsequently radiating to diverse potential uredinial-telial hosts, further specializing on them, and eventually leading to speciation at habitats, where the two hosts of different life cycle stages co-occur in close proximity. Repeated co-related evolution between Ochropsora fungi and their host plants, followed by range expansion/reduction, migration, disjunction, further speciation, and extinction have undoubtedly shaped the species diversity in the modern disjunct distribution of Ochropsora in the Northern Hemisphere. As described above, the same or similar eco-physiological preference of plant taxa, that serve as the host of all life cycle stages of Ochropsora species, to the temperate mesic forest habitat often results in literally sympatric occurrence of two or more spermogonial-aecial and uredinial-telial taxa at each of habitat in their distribution range. Co-occurrence of potential spermogonial-aecial and uredinial-telial host plants at the same habitat fulfils the prerequisite for host-jump or host-shift in diversification and eventual speciation of the rust fungi (McTaggart et al., 2015; Roy, 2001; Thines, 2019). Ono (2008) proposed a model for the diversification of heteroecious rust fungi and co-related speciation with their hosts in general. This model can be applied, with some refinement, to Ochropsora as discussed here.

The modern geographic disjunction of Ochropsora in eastern Asia (11 species), eastern North America (3 species), and northwestern Europe (1 species) (Fig. 31) can be superimposed on the biogeographic disjunction of remarkably similar floras between eastern Asia and eastern North America (Boufford & Spongberg, 1983; Manchester, 1999; Tiffney, 1985a; Wolfe, 1969). Therefore, currently observed high Ochropsora species diversity in eastern Asia and low diversity in eastern North America might be discussed in line of the developmental history of the eastern Asian and eastern North American disjunction of Tertiary relict floras (Manchester, 1999; Milne & Abbott, 2002; Tiffney, 1985a, 2000; Tiffney & Manchester, 2001; Wolfe, 1969). The disjunction of Tertiary relict floras has resulted from complex processes, involving migration/dispersal, speciation, extinction, vicariance, evolutionary convergence and stasis (Wen, 1999; Xiang et al., 2000). The relict floras are represented by disjunct taxa of close similarity and/or phylogenetic relationships. Those taxa were once considered as pairs of the same species, but are now considered, in most cases, to be closely related, but distinct, species of the disjunct genera (Wen, 1999; Xiang et al., 2000). The timing of the disjunctions might have been diffused in a geological time scale among different plant taxa, but the importance of the Miocene in the development of the disjunct pattern has been emphasized (Tiffney, 1985a; Wen, 1999; Wen et al., 2010; Xiang et al., 2000). Without fossil records, comprehensive molecular phylogenetic analysis based on multigene sequences, and time estimates for the divergence of Ochropsora species, only a simple inference on the historical biogeography of Ochropsora is possible, which, however, might serve as a working hypothesis for a future study.

Fig. 31 - Disjunct distribution of Ochropsora in the Northern Hemisphere. Broken lines demarcating distribution ranges of Ochropsora in the tree geographic regions are approximation estimated from collection records. When Ochropsora panacis is removed, the eastern Asian distribution range is much reduced to the eastern edge of Eurasia. This fungus is a single Ochropsora species to be found in Shaanxi and Guangxi (China) in the eastern extension of the Himalayas. Blank map of the Northen Hemisphere was downloaded from https://commons.wikimedia.org/wiki/File:Worldmap_northern.svg.

There is a copious literature in the past geological and climatic changes in relation to the origin, evolution, maintenance, and extinction of Tertiary relict floras and vegetations in the Northern Hemisphere (e.g., Loidi & Marcenò, 2022; Manchester, 1999; Milne & Abbott, 2002; Morley, 2011; Tiffney, 1985a, b, 2000; Tiffney & Manchester, 2001; Wen, 1999; Wen et al., 2010; Wolfe, 1969; Xiang et al., 2000). The following discussion is based primarily on this literature. High latitude regions of eastern Eurasia and North America were connected by the Bering Land Bridge (BLB) and North America and northern Europe by the North Atlantic Land Bridge (NALB) during the late Cretaceous through the Paleogene. This was an epoch during which period many modern angiosperm families evolved, forming widespread evergreen and mixed hardwood forests (boreotropical flora of Wolfe, 1969; megathermal forests of Morley, 2011) under warm and mesic conditions. During the early to the mid Cretaceous, earlier than Tiffney’s (1985a) speculation, Ranunculaceae and Papaveraceae, that contain host genera of Ochropsora, are inferred to have originated and rapidly diversified together with other herbaceous angiosperm taxa as members of forest floor communities concomitantly with the raise of woody angiosperms (Li et al., 2019; Peng et al., 2023; Wang et al., 2016). According to Aime et al. (2018), the most recent ancestor to all extant rust taxa diverged at the boundary of early and mid Jurassic (older than the estimate by McTaggart et al., 2016). Early co-diversifications of the rust fungi and their angiosperm host plants were estimated to occur during the Cretaceous period (Aime et al., 2018; McTaggart et al., 2016). According to Peng et al. (2023), Papaveraceae differentiated in the mesophytic forests in Asia during the early Cretaceous and subsequently migrated from Asia to western North America via BLB in the mid to late Cretaceous. This might suggest a possible migration and/or range expansion of a hypothetical ancestor of Ochropsora lineages evolved in Eurasia.

NALB broke up in the early Eocene, but chains of small islands remained for some period, which events greatly reduced the probability of direct plant migration between Europe and North America. By contrast, deciduous taxa adapted to cooler and seasonal climates might have migrated between eastern Asia and North America via BLB. The period from the latest Oligocene to the earliest Miocene was characterized by the recovery of global warmer climates. The renewed warm climates permitted evolution of many modern deciduous and herbaceous taxa, forming the mixed mesophytic forests comprised of deciduous and evergreen trees and forest floor herbs. The global temperature gradually declined with fluctuations until the mid Miocene (Milne, 2006; Morley, 2011) and significantly dropped from this era onwards (Morley, 2011; Tiffney & Manchester, 2001; Wolfe, 1969). This rapid climate change might have initiated independent divergence of plant taxa between eastern Asia and eastern North America (Milne & Abbott, 2002; Morley, 2011; Tiffney, 1985a). However, it is not clear how many taxa evolved independently in one region and migrated via BLB to the other, and how many taxa evolved in parallel in the two regions from common ancestors in the once widespread boreotropical flora (Tiffney, 1985a; Wolfe, 1969).

Diverse herbaceous taxa in the widespread mesophytic mixed forests were particularly adapted to flowering in the stable forest floor in a short period in the spring (“spring ephemerals”) before the forest canopy became completely closed. As to the spermogonial-aecial hosts of Ochropsora species, Ehrendorfer et al. (2009) estimated that the monophyletic Anemone s.s. diverged in the mid Miocene. This estimate is younger than the estimate in the late Oligocene by Sramkó et al. (2019). Subsequently, Anemone in the subgenus Anemone successively diverged in a relatively short period of time in the late Miocene. The subtribe Corydalinae (including Corydalis and Dicentra) diverged in the mid Eocene through Oligocene (Peng et al., 2023). Majority of extant lineages of Corydalis diverged from the early Miocene onward and Dicentra in the mid Oligocene and later (Peng et al., 2023; Pérez-Gutiérrez et al., 2015). According to Pérez-Gutiérrez et al. (2015), the diversification of Dicentra began in western North America during the Oligocene-Miocene transition. During the diversification process, three independent migrations occurred, and D. cucullaria was estimated to migrate from western North America to eastern North America from the Miocene onward. This period might be the time for Ochropsora to diversify and to migrate and/or expand their range with their hosts. The phylogenetic trees reconstructed by McTaggart et al. (2016) and Aime et al. (2018) showed that majority of extant rust lineages had diverged in the Miocene. Phylogeographic studies of the eastern Asian-eastern North American disjunct plant taxa revealed that many temperate disjunct lineages showed relatively young crown group ages dating from the Miocene to the Pliocene, while much older age was shown for their stem groups (Wen et al., 2010). This general pattern in Tertiary disjunct taxa might be applicable to the rust fungi. From Aime and McTaggart's (2021) molecular-phylogeny-based classification, together with divergence time estimates by McTaggart et al. (2015) and Aime et al. (2018), modern Ochropsora lineages are speculated to have diverged, as with other modern rust lineages, in the disjunct geographic regions during the Miocene.

Of particular interest in the disjunct distribution in Ochropsora are “species pairs.” They are seemingly in sister species relationships between the three separate geographic regions (Figs. 29, 30). In the eastern Asian-northwestern European disjunction, O. ariae and O. asiatica are similar in host-alternating between Anemone (Ranunculaceae, spermogonial-aecial hosts) and Rosaceae plants (uredinial-telial hosts). Their common uredinial-telial hosts include species of Amelanchier, Aruncus, Pyrus, and Sorbus. Because of almost the same life cycle pattern and host preference and because of lack of close comparative morphological study, the eastern Asian fungus had long been referred to as conspecific with the northwestern European O. ariae, until this study (Hiratsuka et al., 1992; Ito, 1938; Ono, 2006). It is now clear that the eastern Asian fungus is species distinct from the northwestern European fungus (see the Taxonomy section). It is puzzling that Ochropsora species host-alternating between Anemone and rosaceous plants is lacking in North America even though the actual/potential hosts for both spermogonial-aecial stages (Anemone) and uredinial-telial stages (particularly Aru. dioicus and Aru. silvester) are widely distributed in the mid latitude of the Northern Hemisphere. Insufficient exploration for fungi host-alternating Anemone and rosaceous plants, poor understandings of past changes in their geographic ranges, particularly during the mid Miocene-Pliocene period, and total lack of molecular phylogeographic and divergence time estimate studies do not permit any reliable inference on their evolution and geographic disjunction. Nonetheless, one plausible interpretation might be that a hypothetical ancestral species, host-alternating between Anemone and rosaceous plants, was once widespread in the mesophytic forest floor habitat of temperate mixed deciduous forests, spanning eastern Asia, eastern North America, and northwestern Europe via BLB and NALB. After sundering these land bridges, the former in the late Miocene and the latter in the early Eocene, disjunct fungus populations and their hosts independently diverged and eventually speciated, with total extinction in North America. This means that the O. asiatica in eastern Asia and O. ariae in northwestern Europe are not sister species.

Another seemingly similar relationship is observed in a species pair, whose uredinial and telial stages occur on Laportea (Urticaceae) between eastern Asia and eastern North America. Ochropsora laporteae produces its spermogonial-aecial stages on An. flaccida (Ranunculaceae) in eastern Asia, while O. dicentrae on D. cucullaria (Papaveraceae) in eastern North America. Host-jump might have been involved in the change in the spermogonial-aecial hosts from an ancestral Anemone to D. cucullaria after the latter speciated in western North America in the Oligocene-Miocene transition and further migrated to eastern North America from the Miocene onward (see above). During this period, O. dicentrae might have been exiting across northern North America but might become extinct in western North America. Probably the same interpretation could be applicable to the relationship between O. tanakae, host-alternating between Cory. fumarioides subsp. azurea (Papaveraceae) and Amp. edgeworthii (Fabaceae), in eastern Asia and O. cumminsii, being assumed to host-alternate between D. cucullaria and Amp. bracteata, in eastern North America. A hypothetical common ancestor to Amp. edgeworthii and Amp. bracteata producing the uredinial-telial stages might have migrated from eastern Asia to eastern North America, where the ancestral fungus shifted its spermogonial-aecial stages from Corydalis to Dicentra in the understory of mixed deciduous forest, eco-physiologically similar to the habitat where the ancestor evolved in eastern Asia. Through host-shift in the spermogonial-aecial stages, the two ancestral fungi speciated, independent of each other, in the two geographic regions. Perhaps, only O. dicentrae and O. cumminsii represent a true sister-species relationship in Ochropsora. Both species co-occur under mesophytic deciduous hardwood forests in eastern North America (states of Indiana and Tennessee). Although the spermogonial-aecial host for the latter species was not yet determined, it is likely to be D. cucullaria (see above). From this common host, two fungi diverged by host jump to Laportea and Amphicarpaea, that likely happened in recent geological time (perhaps in the late Miocene or later, see above).

The rust/host phylogeny reconciliation analysis is a powerful method to determine how the rust fungi have evolved with their host plants under intimate biotrophic relationships (Aime et al., 2018; Charleston, 1998; Roy, 2001). Although divergence time estimates were often not congruent between different analyses, primarily because different molecular clock calibrations were employed (Aime et al., 2018; Milne, 2006; Xiang et al., 2000), divergence time estimates by a molecular clock method is also useful to see how rust taxa have shaped their diversity in a geological time scale. Comprehensive molecular phylogenetic analyses of Ochropsora and its allies and their ranunculaceous and papaveraceous hosts must be undertaken, which are then followed by a rust/host phylogeny reconciliation analysis. Exploration of more Ochropsora species in wider geographic range and more diverse habitats is of primary importance. Disclosing biological nature, i.e., host preference, life cycle pattern, and geographic distribution, are prerequisite to delimit species, which are then subjected to molecular phylogenetic analyses. All these efforts will open up a broad and fine-grain view of the evolutionary events on diversification and speciation in the rust fungi, which will in turn provide a more reasonable interpretation for suprageneric classification of the Pucciniales.

All experimental works in this study comply with the current laws of the country where they were undertaken.

Ochropsora specimens including types were loaned from the following herbaria/fungarium: Botanischer Garten und Botanisches Museum Berlin-Dahlem, Freie Universtät, Berlin, Germany (B); Conservatoire et jardin botaniques de la ville de Genève, Switzerland (G); the Hiratsuka Herbarium, Tokyo, Japan (HH); the Komarov Botanical Institute, Saint Petersburg, Russia (LE); the Arthur Herbarium (now Fungarium), the Department of Botany and Plant Pathology, Purdue University, West Lafayette, U. S. A. (PUR); the Swedish Museum of Natural History, Stockholm, Sweden (S); the Hokkaido University Museum, Sapporo, Japan (SAPA); the Faculty of Life and Environmental Sciences, the University of Tsukuba, Tsukuba, Japan (TSH); and Eidgenössische Technische Hochschule Zürich, Switzerland (ZT). I thank Dr. A. Gontcharov, Institute of Biology and Soil Sciences, Russian Academy of Sciences Far East Branch, Russia, for translation of Tranzschel’s Russian literature to English. Technical assistance for SEM operation and observation was provided by Drs. I. Okane and J. P. Abe, the University of Tsukuba, for which I am grateful. This work was supported by JSPS KAKENHI Grant Number 18570081.

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