莴苣上发现一种新的核盘菌菌核病

A NEW KIND OF LETTUCE DROP CAUSED BY SCLEROTINIA SP. IN CENTRAL CHINA

从湖北省神农架莴苣上分离到一种产菌核病原真菌。这种真菌在培养特性上同核盘菌、三叶草核盘菌和小核盘菌既存在着明显差异，又存在着相似之处。其菌核易萌发成子囊柄，但在一般散射光下柄顶端难以发育成子囊盘。对偶得的１枚子囊盘观察表明这种真菌符合核盘菌属真菌的特征，并且同核盘菌属３个近缘种的菌株不同。可溶性蛋白质和多种酶同功酶电泳分析结果表明这种真菌不同于核盘菌属的３个常见种，但同它们亲缘关系较近。这种新菌核病的初侵染来源是菌核萌发产生的菌丝，通过病健接触构成再侵染，在病组织上形成菌核越冬越夏。离体和活体致病性测定结果表明这种真菌只能侵染莴苣，不能侵染油菜、小白菜、萝卜和胡萝卜。

A study was conducted to investigate the disease cycle and host range of a new sclerotium forming pathogen, Sclerotinia sp.strain Let 19,which was isolated from lettuce in central China.Results of pathogenecity tests showed that hyphae from myceliogenically germinatedsclerotia readily caused infections on uninjured lettuce leaves but they caused infections of other plants such as rapeseed only on injured leaves.Also,the fungus was not pathogenic to Chinese cabbage,radish and carrot.The optimum temperature for growth of Sclerotinia sp.strain Let 19 was 20℃ and its growth rate was slower than Sclerotinia trifoliorum .Sclerotia of Let 19 germinated readily to produce stipes,but the stipes rarely developed into apothecia under diffused light.Results of preliminary electrophorectic studies of soluble proteins and enzymes showed that strain Let 19 belongs to the genus Sclerotinia and it is distinctively different from S.sclerotiorum and S.minor which are known pathogens of lettuce drop.