中文摘要：

在内蒙古通辽市、包头市和巴彦淖尔市郊区大棚蔬菜种植区采集菠菜幼苗猝倒病病株,采用形态学和分子生物学方法对分离得到的病原物进行鉴定,并采用平板法测定代表菌株的致病性。结果表明：从82份病样中共获得60株腐霉菌株,分别为德里腐霉（Pythium deliense Meurs）、瓜果腐霉〔Pythium aphanidermatum（Edson）Fitzp〕和终极腐霉（Pythium ultimum Trow var. ultimum）。这3种腐霉均为菠菜猝倒病致病菌,但是发病率有所不同,P.deliense的发病率最高,为85.7%;其次是P.aphanidermatum,发病率为42.9%;发病率最低的是P.ultimum var. ultimum,为28.6%。

英文摘要：

The samples of damping-off spinach seedlings were collected from the greenhouses in Tongliao, Baotou and Bayannur cities of Inner Mongolia. Pathogens were identified by morphological and molecular analysis, and pathogenicity tests of representative isolate of each species was carried out by seedlings infestation method. The result indicated that a total of 60 Pythium isolates were obtained from 82 plant samples. These isolates were identified as P. deliense, P. aphanidermatum and P. ultimum var. ultimum. Pathogenicity tests have proved that the Pythium species are pathogenic, causing damping-off, but with different disease severity. Among them P. deliense were the most pathogenic （infection rate 85.7%）, the next was P. aphanidermatum （ infection rate 42.9% ）, and the lowest was P ultimum var. ultimum （ infection rate 28.6% ）.