An investigation was made to estimate the damage of Cercospora leaf spot caused by Cercospora beticola Sacc. in sugar beet, Beta vulgaris var. rapa Dumot. The disease in field grown sugar beet plants was controlled by spraying with copper fungicide and therefore this chemical was used for establishing different degrees of damage. When the seeds were sown in the Tohoku district in late April, the damage was most severe at forty leaves stage of the plant. At the stage, generally, the top growth of the plants was most vigorous. When the infection was severe, the plants showed severe defoliation and reduction of the vigorous leaves. As the result, reduction of root growth yield and sugar content were corresponded. When the infection occurred after forty leaver stage of the plants, the damage was not so severe.
Two causal viruses were isolated from crotalaria (Crotalaria spectabilis) showing yellow ringspot and mosaic symptoms. The first virus was identified with bean yellow mosaic virus. The virus was transmitted mechanically and also by Myzus persicae. The hosts of this virus were crotalaria, broad bean, bean, soybean and Chenopodium amaranticolor. In electron microscopy using dip method, long flexuous thread-like particles were observed, and the length of them was 700-800mμ. Juice from diseased broad bean leaves reacted positively with antiserum of bean yellow mosaic virus (Komuro and Tochihara, 1964) in a slide flocculation test. The second virus was identified with tobacco ringspot virus. The virus was transmitted mechanically and also by Myzus persicae. The host range of this virus was comparatively wide, namely, aster, zinnia, Nicotiana tabacum (Bright Yellow, Xanthi), N. glutinosa, petunia, okra, broad bean, crotalaria, bean, soybean, turnip, New Zealand spinach, Gomphrena globosa, C. amaranticolor, beet and others. Characteristic ring-like pattern symptoms were observed on N. tabacum (Bright Yellow, Xanthi), N. glutinosa, and Datura stramonium, and these symptoms had a tendency to be masked under high temperature conditions. This virus isolate showed some differences from the hitherto reported tabacco ringspot viruses in noninfectivity to cucurbitaceous plants and in the symptoms on soybean. In electron microscopy using direct negative stain methond, spherical particles of about 26mμ in diameter was observed. The virus in vitro withstood heating at 65°C for 10 minutes, dilution to 5, 000 and 7 day's aging at room temperature. Kahn et al. (1963) reported that bean yellow mosaic virus was isolated from crotalaria, but the disease of crotalaria by tobacco ringspot virus has not yet been reported. This is also the first report in recognition of tobacco ringspot virus in Japan.
イネ白葉枯病菌Xanthomonas oryzae (Uyeda et Ishiyama) Dowson(農業技術研究所保存株H-5809)を脇本氏培地に培養した培養液中にイネ幼根生育抑制物質の存在することが明らかになつた。 この物質を単離するため菌培養液をエーテルで抽出し,それをさらに酸性部に分け,水蒸気蒸溜してその残渣をSilica Gel Column-chromatographyによつて抑制物質を精製し,菌培養液10lから約50mgの結晶を単離し得た。この抑制物質のm.p.は76.5℃で,フェニール酢酸の赤外線吸収スペクトルと同一であつた。またフェニール酢酸との混融試験を試みたが融点降下をしめさなかつた。したがつてこの単離された抑制物質はフェニール酢酸であることが確認された。