菜豆の綿腐病

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In august, 1930, the cottony leak of the bean (Phaseolus vulgaris L.) waas found in a farm in the vicinity of Tokyo. The affected beans were coverd with luxuriant fine white mycelium, and the leaves infested were grayish brown, seeming as if water-soaked. From the diseased parts, a pythiaceous fungus was easily isolated. This fungus is quite similar to that which was already described in America as causing the transit or cottony leak disease of the snap bean. The weiters think that their fungus belongs also to Nematosporangium aphanidermatum (EDSON) FITZPATRIK. Morphology of the Fungus : -The prosporangium or plasmato-oogosis is composed of a lobulate, inflatted mass of mycerial branches. It produces a long exit tube at which tip appears a zoosporangium or vesicle as a bubble like sphere. The zoosporangium and the encysted zoospore measure 36.3-45.5 and 9.-512.8μ in diameter, respectibely. The oogonium is spherical, smooth, terminal or intercalary, and measures 16.2-30.5μ×16.2-28.6μ (average 25.0×23.3μ). The antheridium is terminal or intercalary, broadly clavate, 7.6-19.0×6.7-16.2μ (average 12.7×10.5), and one to two to each oogonium. The oospore is spherical, smooth, yellowish brown, not filling the oogonium, and measure 12.4-24.8×12.7-22.9μ (average 18.8-18.0μ). Physiology of the Fungus :-The fungus grows readily on many culture media. Its growth is good on oatmeal-, potato-, and corn meal-agare and best on the first named one. It is rather good on bean agar and SAITO's soy-onion agar, though no oospore is produced on them. Five other media are seen to be unfavourable for its growth, and no growth at all takes place on apricot agar. The fungus grows at the temperature 10-40℃, and the optimum one lies at about 30℃. The mycelial growth is most luxuriant at 20-24℃; the prosporangium and the oospore are produced most abundantly at 27-34℃ and 22-32℃ respectively. The fungous growth is best at pH 5.25-6.45, and no growth takes place at pH 2.9. When it is cultured in liquid media, the pH of the media changes gradually, and approaches to pH 5.5. Inoculation Experiment:-The pods and leaves of the bean are readilly infected when inoculated with mycelia of the cultured fungus, showing symptoms quite the same as the naturally infected one. The seedlings are also infected, resulting in the damping off. The pods of four legminous plants, the fruits of three solanaceous and two cucurbitaceous plants, and the fruits of the fig are readily infected. The leaves and stems of the egg plant and Datura fastuosa L. are also infected. The seedlings of many kinds of plants are aggected, but some cucurbitaceous and leguminous plants are not infected when there is no wound. The infection occures well at the temperature 22-38℃, and the most favourable temperature for the development of the diseaselies at 27-34℃. This fact explains that this disease occurs only during hot summer season.
日本植物病理学会の論文
1935-12-25

菜豆の綿腐病

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