中文摘要：

为了明确天竺葵腐霉枯萎病的病原菌种类,从内蒙古通辽采集天竺葵腐霉枯萎病样品,对病原物进行了分离、纯化和致病性测定,并对病原物进行形态学和rDNA-ITS序列分析鉴定。结果表明,从10个植物样品中分离得到16个腐霉菌株,分别属于终极腐霉Pythium ultimum var.ultimum、瓜果腐霉P.aphanidermatum和两个与P.ultimum var.ultimum相似的待定种。其中,P.ultimum var.ultimum的分离频率为75%、P.aphanidermatum的分离频率为12.5%,两个腐霉待定种的分离频率均为6.25%;P.ultimum var.ultimum是优势类群。致病性测定结果表明,4种腐霉菌都能引起天竺葵腐霉枯萎病,与自然发病症状相同,其中P.ultimum var.ultimum和P.aphanidermatum的致病性较强,发病率分别为71.4%和85.7%。

英文摘要：

The diseased pelargonium hortorum samples infected with Pythium blight were collected from Tongliao City, Inner Mongolia, and totally 16 Pythium isolates were obtained. Based on morphological characteristics and rDNA-ITS sequence analysis, the pathogens were identified as Pythium ultimum var. ultimum, P. aphanidermatum, Pythium sp.1 and Pythium sp.2. P. ultimum var. ultimum was the most dominant（75% of the total isolates）, followed by P. aphanidermatum（12.5%） and two other Pythium species（both 6.25%）. Pathogenicity tests have proved that the four Pythium species are pathogenic, producing blight symptoms. P. ultimum var. ultimum and P. aphanidermatum are more pathogenic, with infection rate of 71.4% and 85.7% respectively.