大豆炭腐病病原菌鉴定

为有效防冶大豆炭腐病,对最近在北京和天津两块大豆田发生的疑似大豆炭腐病病原菌进行了鉴定.在PDA培养基病原菌上分离物生长较快,菌落灰色,产生大量直径为49.8～111.4 μm的黑色菌核.接种表明,选择的5个分离物对大豆品种合丰25的幼苗致病,且各分离物从病株上重新分离率为100%.用通用引物ITS4/ITS5扩增5个分离物的rDNA-ITS序列区和测序,通过与Genbank数据库比对,5个分离物与菜豆壳球孢菌分离物序列的相似性为97%～99%.用菜豆壳球孢菌的特异性引物MpKF1/MPKR1进行检测,在5个分离物中均扩增出350 bp的特征片段.基于病害症状、病原菌形态、致病性和分子特征,鉴定这5个分离物为菜豆壳球孢菌.该病害在华北地区尚属首次报道.

Identification of Pathogen Causing Soybean Charcoal Rot

Charcoal rot,causing by Macrophomina phaseolina (Tassi)Goid is an important soybean disease in the world. In late August 2005 and 2007, symptoms of charcoal rot-like were observed on soybean plants in one field in Tian-jin and Beijing, respectively. Both fields had more than 80 % disease incidence, with extensive premature death prior to pod-filling stage. Fungal isolations were made from the diseased stem tissue in order to identify the causal agent. Five re-sulting isolates were cultured on potato dextrose agar at 30℃ ,and were identified as M.phaseolina based on the gray col-or of the colony and the presence of microsclerotia 49.8 to 111.4 μm in size.Pathogenicity was performed by inoculation of 2-week-old seedlings of cv. Hefeng 25 using hypocotyl inoculation and cut stem techniques. All inoculated plants showed dark brown to black lesions. For each isolate tested, M. phaseolina was resolated from inoculated plants. To con-firm the morphological identification, the rDNA-ITS region of the five isolates was amplified with universal primer ITS4 and ITS5.The obtained ITS sequences (one sequence Gen Bank accession No. FJ175382) were aligned with GenBank and showed 97 % - 99 % similarity with isolates of M. phaseolina . PCR specific primers MpKFl and MPKR1 for M. phaseoli-na were used to detect genome DNA of the five isolates, the primers produced single amplified product of 350 bp with the five isolates, and the results confirmed them as M. phaseolina . Up to now, only two notes about its occurrence were pub-lished in Liaoning Province and Shandong Province, and the causing pathogen did not have been identified. This is the first report of occurrence of charcoal rot of soybean in Northern China.