一种新发生的大豆茎枯病病原菌鉴定

鉴定了一种新发生的大豆茎枯病病原菌。在酸化PDA培养基上所有病原菌分离物菌落呈白色,气生菌丝呈密集的卷毛状,有时部分区域显黄绿色;培养基背面开始无色,随后产生大的、扩展的黑色子座。在接种的大豆茎秆上产生大小不等的黑色子座和分散的分生孢子器。共产生2类分生孢子,其中α型分生孢子丰富,无色,单孢,椭圆至纺锤状形,大小4.05～7.57μm×1.48～3.25μm,含2个油滴;β型分生孢子极少见,无色,线形。在培养基及大豆茎秆上未发现有性态。致病性测定表明选择的分离物引起合丰25大豆100%植株发病和种子腐烂。用AluI、RsaI和HhaI酶切通用引物对ITS4/ITS5扩增的rDNA-ITS产物,所有分离物都产生与大豆拟茎点种腐病菌Phomopsis longicolla一致的酶切谱带;序列比对发现测序的2个分离物ITS序列与GenBank中9个P.longicolla分离物ITS序列100%同源。这是我国首次报道大豆田间发现P.longicolla,而且能引发严重的大豆茎枯病。

Pathogen identification of a newly occurred soybean stem blight in China

The pathogen causing soybean stem blight disease was newly identified.The isolate produced floccose dense white colonies with occasional green-yellowish areas on acidified PDA medium was newly identified.The stromata were large,black and widespread.It was observed that the pycnidia produced both alpha-and beta-conidia when inoculated on soybean stem.Alpha-conidia were hyaline,ellipsoidal to fusiform,and guttulate with sizes of 4.05 to 7.57μm ×1.48to 3.25μm.Beta-conidia were rare,hyaline,filiform and hamate.Four isolates selected caused seeds rotten and 12-day-old seedlings diseased when inoculated on soybean cultivar Hefeng 25.To indentified the pathogen,rDNA-ITS fragment was amplified using universal primer ITS4 and ITS5,and followed by digesting with Alu I,Rsa I and Hha I restriction enzymes. Phomopsis longicolla characteristic band spectrum was shown in every isolate PCR products.Two isolated ITS sequences were identical to 9 isolates of P.longicolla in GenBank.The results indicated that the pathogen of severe soybean stem blight was just P.longicolla.It was the first report of P.longicolla being isolated from soybean in China.