Mycoscience
Online ISSN : 1618-2545
Print ISSN : 1340-3540
Volume 48, Issue 4
Displaying 1-9 of 9 articles from this issue
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  • Rinka Yokoyama, Daiske Honda
    2007 Volume 48 Issue 4 Pages 199-211
    Published: 2007
    Released on J-STAGE: March 31, 2023
    JOURNAL FREE ACCESS

    The genus Schizochytrium sensu lato has been characterized by successive binary division of its vegetative cells. However, the molecular phylogeny strongly suggests that this genus is not a natural taxon, because the original and recorded strains that have been identified as Schizochytrium spp. separately form three well-supported monophyletic groups in the 18S rRNA gene tree. These three groups are clearly distinguishable by their combined morphological characteristics and the profiles of the polyunsaturated fatty acids and carotenoid pigments they contain, although these are hard to distinguish using only a single feature. Therefore, three different genera are proposed to accommodate these three groups, i.e., Schizochytrium sensu stricto, Aurantiochytrium, and Oblongichytrium gen. nov.

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  • Satoshi Sekimoto, Kishio Hatai, Daiske Honda
    2007 Volume 48 Issue 4 Pages 212-221
    Published: 2007
    Released on J-STAGE: March 31, 2023
    JOURNAL FREE ACCESS

    The SSU rRNA, LSU rRNA, and cox2 genes of an unidentified Haliphthoros-like marine oomycete (NJM0034) and Haliphthoros milfordensis (NJM0131) were sequenced, and their phylogenetic relationships are analyzed and discussed. All phylogenetic trees showed that NJM0034 and NJM0131 were branched before separation of the two main saprolegnian and peronosporalean clades. These data suggest that the clear phylogenetic separation of those marine oomycete endoparasites from the two main oomycete clades. Excepting the LSU rRNA gene tree, NJM0034 and Haliphthoros spp. did not form a monophyletic group. On the other hand, H. milfordensis NJM0131 clustered with H. philippinensis SANK 15178, not with H. milfordensis NJM9434 in the cox2 amino acid sequence (COII) tree. This result strongly suggests that a taxonomic reinvestigation of the genus Haliphthoros should be considered.

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  • Binh-Nguyen Truong, Koei Okazaki, Toshimitsu Fukiharu, Yuko Takeuchi, ...
    2007 Volume 48 Issue 4 Pages 222-230
    Published: 2007
    Released on J-STAGE: March 31, 2023
    JOURNAL FREE ACCESS

    Toxocysts of the genus Pleurotus are blastoconidia-like ovoid structures surrounded by a liquid droplet containing a toxin that paralyzes nematodes. This study investigated toxocyst development using a strain S396 of Pleurotus cystidiosus subsp. abalonus (subgen. Coremiopleurotus). The surface of the liquid droplet was found to be an elastic envelope. When a nematode touches the toxocyst, the envelope adheres to the worm and bursts. Toxocysts are induced simultaneously with coremia formation in the absence of nematodes and developed only from aerial hyphae in which nuclear division had ceased. In the early stage of toxocyst development, liquid springs repeatedly from the tip of the sterigma-like stipe before ovoid (blastoconidium-like structure) formation. A certain substance in the liquid might polymerize to form the envelope while the ovoid simultaneously budded in the droplet. The nucleus tends to locate near the toxocyst, especially in early stage of toxocyst development. Each dikaryotic cell predominantly formed one or two toxocyst(s) while each monokaryotic cell predominantly formed one. In rare cases, a nucleus existed in the toxocyst, suggesting the possibility that the toxocyst is a vestigial blastoconidium.

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  • Mathew John Irwin, John David William Dearnaley, Jeremy James Bougoure
    2007 Volume 48 Issue 4 Pages 231-239
    Published: 2007
    Released on J-STAGE: March 31, 2023
    JOURNAL FREE ACCESS

    In this study, we have identified the root-associated fungi of a common species of terrestrial orchid across its range in eastern Australia. We have amplified and cloned fungal ITS DNA extracted from roots of 15 Pterostylis nutans R. Br. plants from six separate geographic localities. Sequencing and GenBank comparison demonstrated two species of Ceratobasidium fungi as the main fungal partners of the orchid. Uncommon fungal associates included homobasidiomycete species such as a Gymnomyces sp. and a Tricholoma sp., Leptodontidium orchidicola, and an unidentified soil fungus. These results demonstrate that specificity for fungal partners occurs in P. nutans and reinforces the idea that conservation measures for endangered Australian orchids must include ex situ perpetuation of fungal symbionts as well as plant material.

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  • Izumi Okane, Akira Nakagiri
    2007 Volume 48 Issue 4 Pages 240-249
    Published: 2007
    Released on J-STAGE: March 31, 2023
    JOURNAL FREE ACCESS

    Two xylariaceous fungi were isolated from a nest of a termite, Odontotermes formosanus, that was incubated in a laboratory after collecting from Iriomote Is., Okinawa Pref., in Japan. One of the two fungi was identified as Xylaria angulosa on the basis of the morphology of branched stroma produced on medium, tiny asci, and ascospores having a germ slit. Another fungus is an anamorphic fungus that produces synnemata up to 50 mm long from which dendritic conidiophores branch out. Unicellular conidia are holoblastically produced on a sympodially proliferating conidiogenous cell. Such morphological characters resemble those of the genus Geniculosporium. However, its distinctive synnema formation and dendritic conidiophores do not assign the fungus to Geniculosporium or other known genera and warrant establishment of a new genus. The phylogenetic tree based on the ITS regions of rDNA shows that the fungus is nested in the cluster of the genus Nemania (Xylariaceae), whose species have mainly Geniculosporium-like anamorphs. We describe here the present anamorphic fungus as Geniculisynnema termiticola gen. et sp. nov., and discuss its phylogenetic and ecological relationships to xylariaceous fungi, especially termiticolous species.

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