大豆茎褐腐病病原菌鉴定

Pathogen identification of brown stem rot of soybean

对新发生的引起大豆茎维管束和髓褐腐的病原菌进行鉴定。该病原分离物在PDA培养基上的菌落扁平,致密,不规则圆形,白色到浅灰褐色,具放射状褶皱突起,菌落边缘粗糙不整齐,或带有缺刻;在GBA培养基上菌落白色至灰色,菌丝紧贴培养基,气生菌丝稀少,菌落圆形,边缘整齐。在GBA培养基上分离物产生分生孢子,分生孢子卵形至椭圆形,无色;单胞,或形成有分隔的细胞;平均长度为(3.0～5.1)μm×(2.1～3.3)μm。致病性测定表明分离物能100%引起合丰25大豆植株出现典型大豆茎褐腐病症状。引物ITS1/ITS4在分离物中扩增的产物与GenBank中Phialophora gregata分离物序列的相似性达99%。利用大豆茎褐腐病菌的特异引物BSR1/BSR2在分离物中扩增出483bp的特异性条带。研究结果表明,上述分离物确为大豆茎褐腐病菌。

The pathogen causing browning of vascular system and pith of soybean in China was identified using morphological and molecular characteristics. Colonies of the isolates on PDA medium developed in the form of a flat, dense, roughly circular, white to putty-coloured or grey mat, with radial folds and a variable, usually finely lobate or notched margin. Colonies on GBA medium were white to grey, circular, with smooth edge whose mycelia adhered to medium and the aerial mycelia were sparse. On GBA medium, the conidia were produced, which are hyaline, aseptate, uniseptate or multiseptate, ovoid to elliptical, （3.0 ~ 5.1） ×（2.1 ~3.3）？m. Typical symptoms of brown stem rot occurred in 100% of seedlings when inoculated with the isolates on soybean cultivar Hefeng 25. To verify the pathogen, rDNA-ITS fragments of the isolates amplified using primers ITS1 and ITS4 were sequenced, and 99% of sequence similarity reached between the isolate and a Phialophora gregata isolate （GenBank Accession No. U66728.1） in Genbank. The specific 483-bp DNA products were amplified from the isolates using primers BSR1/BSR2 specific to P. gregata. The above results indicated the isolates were P. gregata.