江苏水稻旱育秧“黄枯”病原鉴定及致病力研究

 从江苏13个市采集肥床旱育秧"黄枯"标本1030份,分离后获784株菌。经鉴定和致病性测定,752株为致病菌,分属4属11种真菌:(1)镰孢属(Fusarium),占74.0%,有6个种,分别为禾谷镰孢(F.graminearum Schw.)、尖孢镰孢(F.oxysporum Schlecht.)、木贼镰孢[F.equiseti (Corda) Sacc.]、串珠镰孢(F.moniliforme Sheld.)、半裸镰孢(F.semitectum Berk.et Rav.)和雪腐镰孢[F.nivale (Fr.) Ces.],其中禾谷镰孢最多,占病菌总数的25.3%;其次是尖孢镰孢、木贼镰孢和串珠镰孢,分别占16.2%、13.3%和10.2%;而雪腐镰孢仅占1.1%。(2)丝核属(Rhizoctonia),有立枯丝核(R.solaniKühn),占14.6%。(3)平脐蠕孢属(Bipolaris),占7.4%,主要是麦根腐平脐蠕孢[B.sorokiniana (Sacc.) Shoem.],占7.0%,而稻平脐蠕孢[B.oryzae (Breda.de Haan) Shoem.]仅为0.4%。(4)腐霉属(Pythium),占4.0%,有瓜果腐霉[P.aphanidermatum (Eds.) Fitzp.]和链状腐霉(P.catenulatum Matth.)。病菌种类及其比例因地区和苗床土类型的不同存在一定差异。接种试验表明,不同病菌致病力和引起的症状类型差异较大。腐霉、禾谷镰孢、串珠镰孢和麦根腐平脐蠕孢引起的发病率均为100%,而半裸镰孢和雪腐镰孢仅40%左右。多数病菌能够引致稻苗的"黄枯",并且茎基部有褐色病斑。引起死苗的主要是腐霉、麦根腐平脐蠕孢和禾谷镰孢,而串珠镰孢往往引起稻苗的徒长或矮化。

IDENTIFICATION AND PATHOGENICITY STUDY OF FUNGI CAUSING YELLOWING AND BLIGHT OF RICE SEEDLINGS ON DRY SEEDBED IN JIANGSU

784 strains of fungi were obtained by the isolation of 1030 samples of rice seedling showing yellowing and blight on dry seedbed from 13 places of Jiangsu Province. 752 of the strains were identified as plant pathogens, which belonged to 11 species of 4 fungal genera:(1) Fusarium, including F.graminearum Schw., F.oxysporum Schlecht., F.equiseti (Corda) Sacc., F.moniliforme Sheld., F.semitectum Berk. et Rav. and F.nivale (Fr.) Ces., made up 74.0%.Among them F.graminearum isolates was the most abundant with the ratio of 25.3%; F.oxysporum,F.equiseti and F.moniliforme ranked the next, with the ratios of 16.2%,13.3% and 10.2%, respectively; F.nivale isolates had the least proportion which was only 1.1%. (2) Rhizoctonia, including only one species R. solani Kühn, accounted for 14.6%. (3) Bipolaris amounted to 7.4%, in which B.sorokiniana (Sacc.) Shoem. had much more isolates than B.oryzae (Breda. de Haan) Shoem. (4) Pythium, which included P.aphanidermatum (Eds.) Fitzp. and P.catenulatum Matth., had the ratio of 4.0%. The inoculation test showed that there were significant differences in the pathogenicity of various species and the symptoms caused by them. The rate of the diseased rice seedlings was 100% by the inoculation of Pythium, F.graminearum, F.moniliforme and B.sorokiniana while that was about 40% due to the infection of F.semitectum and F.nivale. Most species could induce rice seedling yellowing and blight with brown lesions on the stem base. The pathogenic species causing seedling death were mainly Pythium, B.sorokiniana and F.graminearum. In general, F.moniliforme caused seedling etiolation or stunt.