Four isolates of Pseudomonas andropogonis, three of P. stizolobii, and five of P. alboprecipitans were studied comparatively. All the isolates of P. andropogonis and P. stizolobii are practically identical in cultural, physiological, and biochemical properties (except for one isolate of P. andropogonis which is different in respect to Kovacs' oxidase reaction). All isolates are pathogenic on the leaves of sorghum (producing typical red stripes) and bean (forming small brown spots). All cultures of P. andropogonis and one isolate of P. stizolobii could infect white clover, developing black spots on the leaves; the remaining strains are avirulent for this plant. Two isolates of P. stizolobii did not infect corn or clover. From these results, it is concluded that the two pathogens fall into a single species, and constitute pathotypes specialized with respect to host range. Thus, Pseudomonas andropogonis is recommended as the scientific name of the bacterium under consideration, with P. stizolobii as a later synonym.
The isolates of P. alboprecipitans obtained in Japan from corn and teosinte are different from the above mentioned bacteria in such bacteriological properties as nitrate reduction, starch hydrolysis, oxidase reaction, hydrogen sulfide production, etc. They are also different in symptoms and virulence on corn and sorghum. Taking all these factors into account, we presently recommend retention of P. alboprecipitans as a species separate from P. andropogonis; perhaps further study of the nonfluorescent phytopathogenic pseudomonads would eventually provide a different taxonomic conclusion.

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Protomycopsis patelii Pavgi and Thirumalachar causing angular black spot of Phaseolus mungo L. and P. radiatus L., and Protomycopsis thirumalacharii Pavgi causing purple leaf spot of Sesbania grandiflora Pers. are perpetuated from one season to another through desiccated but viable, heat-resistant chlamydospores in the host residue and those developed in vitro in the soil. The heat-resistant mycelium is later consumed in forming the resting chlamydospores in the soil, thus adding another dimension to the initial soil-borne inoculum potential of the disease.

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Phage population in the drainage canal of IRRI Farm was highest from August to October amounting to 6-7×10³/ml. The population in the water of reservoir was the next highest. The population peak in the large irrigation canal came a few months earlier than those in the drainage canal and the reservoir. The count was, however, lowest among the 3 sites. Many new phage strains with the different host range patterns were isolated from the plates used for the above phage population survey as well as from the stock cultures of 6 phages studied by Goto. The host srange pattern of these new phages were so diverse that it was almost impossible to classify them into groups with the host ranges. The reason why the host range patterns were so diverse, and new patterns were so often detected from the stock cultures was studied. It was proved that the colony type mutation associated with the phage susceptibility was involved as one of the most important factors controlling the above phenomenon.

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One hundred and thirty-two isolates of the rice blast fungus (Pyricularia oryzae Cav.) of various sources were tested. Soluble proteins extracted from mycelia and enzymes from culture filtrates were subjected to the polyacrylamide gel disc and thin layer electrophoresis. Two isolate groups were distinguished in the soluble protein patterns and peroxidase zymograms, but these have no significant correlations with the geographical distribution of the isolates or their pathogenicity.
In the non-specific esterase zymograms, 3 types were distinguished and the types showed significant correlations with the geographical distribution of the isolates. The taxonomic and phytopathological significance of these findings were discussed.

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A sap transmissible virus was isolated from a mulberry tree showing both ringspot and filiform-leaf symptoms. Soybean, cowpea, pea, bean, Chenopodium quinoa, Nicotiana clevelandii and sesame were infected with this virus by sap inoculation. Infectivity of the crude sap was lost by heating at 50-60°C for 10 minutes, by aging at 15°C for 3 to 5 days, and by diluting at 10³-10⁴. The virus was transmitted through seeds of soybean, but not transmitted by the aphid, Myzus persicae. When preparations from diseased mulberry leaves were examined under electron microscope using dip method, spherical particles of about 22nm in diameter and elongated particles of about 730nm in length were found, whereas only spherical particles were found in the preparations from infected herbaceous plants. Nine collections of mulberries showing enation, ringspot, filiform-leaf, mosaic and yellows symptoms were tested for the identification of the causal virus by sap inoculations to test plants and by dip method under electron microscope. The sap transmissible virus and the elongated particle were found in all collections. The spherical virus was purified by clarification of homogenized cowpea leaf tissues with carbon tetrachloride, followed by differential centrifugation and sucrose density-gradient centrifugation. Electron microscopic examination of purified preparation showed spherical particles of about 22nm in diameter. Antiserum to the virus did not react with cowpea mosaic virus, tomato ringspot virus, and satsuma dwarf virus. Tubular inclusion bodies containing single rows of spherical particles and characteristic vesicular inclusion bodies were observed under electron microscope in ultra-thin sections of cowpea and mulberry leaves infected with the virus. Healthy mulberries (vars. Hachijo and Kairyo-Nezumigaeshi) were inoculated with the partially purified virus obtained from diseased cowpea leaves by sap inoculation. After 3 to 6 months from inoculation, 4 of 24 inoculated mulberries either showed symptoms of ringspot and mosaic or proved to be infected latent. It is inferred that the virus belongs to NEPO virus group, and the name mulberry ringspot virus is proposed. The nature of the elongated particles remains obscure.

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1) The cellular RNA content was altered by CMV infection. The amount of RNA in the infected cells decreased during the first 24hr after infection, and thereafter increased gradually. It is conceivable that the reduction in RNA content in the early stage of infection resulted from the suppression of cellular RNA synthesis, and that the increase in RNA in the later stage was due to the increase of viral RNA in the cells.
2) Base composition and buoyant density of DNA were not significantly altered by infection. The suppression of cellular RNA synthesis by CMV seems not to be caused by a compositional change of DNA.
3) The rate of histone synthesis changed concurrently with the changes in the rate of DNA synthesis. The change in histone synthesis was not only quantitative but also qualitative; the fractionation of histone revealed a preferential increase in arginine-rich histone fraction.
4) RNA synthesis in isolated calf thymus nuclei was suppressed by the addition of tobacco histone. This inhibitory effect was greater in histone from infected cells than in that from normal cells.
5) These results suggest that the suppression of cellular RNA synthesis by infection is due to the compositional change of histone.

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A taxonomic consideration of some species was carried out to divide into subgenera Euhelminthosporium and Cylindro-Helminthosporium. Conidia of Helminthosporium brizae and H. dematioideum were observed to germinate by the production of lateral germ tubes from the basal cell. The mode of germination of conidia was employed as a key character in separating the two subgenera in Helminthosporium, agreeing to Luttrell's view, and both of the species were preferably placed in the subgenus Cylindro-Helminthosporium. In addition, H. zonatum also was included in Cylindro-Helminthosporium as based on a photograph attached to the original description by Ikata and Yoshida.
From a review of the literature and the writer's observations on Helminthosporia parasitic on Gramineae in Japan, 19 species are enumerated as members of subgenus Euhelminthosporium, and 16 species for Cylindro-Helminthosporium. Only H. arundinis described by Nisikado and by Sawada is excluded because it needs further study to permit a satisfactory disposition.
The host plants of respective subgenera of Helminthosporium clearly fall into two different groups of gramineaceous subfamilies sensu Stebbins and Crampton: i. e., Euhelminthosporium spp. are found to be parasitic on the grasses belonging to either subfamily Oryzoideae, Eragrostoideae or Panicoideae, while only one species, H. sorokinianum Sacc. ex Sorok., occurs on members of Festucoideae. On the other hand, all of the 16 Cylindro-Helminthosporium species occur on grasses of subfamily Festucoideae. It may be inferred that the grasses which are north temperate in distribution as represented by Festucoideae are infected primarily by the species of Cylindro-Helminthosporium, whereas grasses with centers of distribution in the tropics and subtropics, such as Oryzoideae and Panicoideae, are infected primarily by the members of Euhelminthosporium.
This relation apparently holds good in the other foreign species of Helminthosporium, though some exceptions have to be admitted. One of the exceptions is that H. giganteum Heald et Wolf occurs on tropical grasses though it belongs to subgenus Cylindro-Helminthosporium. It is interesting to note that H. giganteum has a very wide host range, as does H. sorokinianum, an exceptional species in Euhelminthosporium.

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The effect of sodium dimethyldithiocarbamate (NaDMDC) on Xanthomonas oryzae, a causative pathogen for bacterial leaf blight of rice plant, was investigated. The growth of X. oryzae in liquid medium was completely suppressed at a concentration of 50μg/ml when the fungicide was added immediately after inoculation, and at the mid-logarithmic growth it was also suppressed about 50 per cent at a concentration of 100μg/ml.
Oxygen uptakes by endogenous respiration and substrate oxidation were slightly accelerated by the concentration less than 50μg/ml, whereas at the higher concentration, the oxygen uptakes were somewhat inhibited, among the several kinds of substrate, succinate oxidation was most markedly inhibited. But succinate dehydrogenase activity in cell-free extracts of X. oryzae was almost not inhibited by 10μg/ml NaDMDC.
The incorporations of amino acids-¹⁴C into protein and of glucosamine-¹⁴C into cell wall were not inhibited even at a concentration of 100μg/ml. The incorporations of uridine-¹⁴C and thymidine-¹⁴C into RNA and DNA respectively were considerably inhibited by 100μg/ml NaDMDC, while adenine-¹⁴C, orotic acid-¹⁴C, glycine-¹⁴C and H₃³²PO₄ were not inhibited at the same concentration. Thus it is assumed that NaDMDC acts against incorporation of nucleosides into nucleic acids. However, the most remarkable inhibition was observed in the lipid synthesis. The incorporation of acetate-¹⁴C into lipid was inhibited approximately 50 per cent by 100μg/ml NaDMDC, and under the presence of glucose the inhibition reached to 90 per cent at the same concentration. Furthermore, the incorporations of pyruvate-¹⁴C and H₃³²PO₄ into lipid were remarkably inhibited.
These results indicate clearly that the possible site of NaDMDC action against X. oryzae may be the process of lipid biosynthesis.

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A kind of bacteriophage which attacks Pseudomonas caryophylli was isolated from the affected carnation plants collected from Hyogo prefecture, Japan, and was named as CaP₁. The fundamental properties of this phage elucidated in this experiment are as follows: CaP₁ phage is tadpole-shaped, which composed of a head of ca. 56mμ in diameter and a tail of 105mμ in length and 18mμ in width. Every isolates of P. caryophylli collected from several localities of Japan were susceptible to the phage. All of the other tested bacteria, 16 species of Pseudomonas (12 phytopathogenic and 4 soil bacteria) and 11 species of other genera, were resistant to the phage. Escherichia coli was also resistant. Activity of the phage was comparatively stable under the temperatures lower than 50°C in distilled water. It was, however, rapidly inactivated at the temperatures higher than 50°C, and was completely inactivated at 57°C for 10 min. The optimum temperature for plaque formation was 30°C, under which the highest plaque forming efficiency was obtained. Nine progeny phages in average were produced from a single host cell after the latent period of ca. 90 min and the following rise period of ca. 100 min in PS medium at 30°C.

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