大豆根腐病腐霉病原鉴定

大豆根腐病是一种严重危害大豆生产的世界性土传病害。大豆根腐病病原复杂，病原鉴定是防治大豆根腐病的前提和基础。2019-2020年从山东省采集大豆根腐病标样432份，采用常规组织分离法对大豆水渍状的根系进行病原菌的分离和纯化，得到了279株菌株，其中52株菌株为腐霉菌（Pythium）。对这52株菌株通过形态学特征和ITS、CoxII和β-tubulin序列分析等分子生物学手段鉴定出3种腐霉菌，分别为瓜果腐霉Pythium aphanidermatum、终极腐霉Pythium ultimum和林栖腐霉Pythium sylvaticum。这3种腐霉菌的分离频率分别为：瓜果腐霉P. aphanidermatum占50%，终极腐霉P. ultimum占34.62%，林栖腐霉P. sylvaticum占15.38%，其中瓜果腐霉P. aphanidermatum为优势菌株。对这3种腐霉菌进行了致病性测定,发现3种腐霉菌均可侵染大豆，重复出大豆根腐病的症状。林栖腐霉P. sylvaticum作为大豆成株期根腐病的致病菌在国内是首次报道。研究结果为大豆根腐病的抗病育种及其防治提供了科学依据。

Pathogen identification of Pythium root rot disease on soybean

Soybean root rot was a worldwide soil-borne disease that reduced soybean production. Pathogen identification is the premise and foundation for soybean root rot control. A total of 432 soybean rotten root samples were collected from main producing areas of Shandong Province in 2019-2020. Strains of 279 fungi were isolated and purified from watery soybean roots by tissue separation method, according to morphological identification and ITS， CoxII， β-tubulin sequence analyze， 52 strains were identified as Pythium aphanidermatum, Pythium ultimum and Pythium sylvaticum. The isolation frequencies of P. aphanidermatum, P. ultimum, and P. sylvaticum were 50%, 34.62% and 15.38%, respectively, and P. aphanidermatum was the dominant pathogen. The pathogenicity test of the above 3 Pythium species was carried out and the symptoms of soybean root rot could be repeated in all the 3 Pythium species. This is the first report of adult stage soybean root rot caused by P. sylvaticum in China. The results could not only increase the pathogen understanding of soybean root rot, but also provide scientific basis for the disease control and resistance breeding.