中国腐霉新记录种Pythium heterothallicum的分离鉴定及致病性测定

2007年9-10月,在甘肃兰州、张掖等地采集玉米、豇豆、葡萄、白菜等作物收获后的耕作层土壤,采用花瓣诱导和组织分离相结合的方法分离土壤腐霉菌。对腐霉菌株经菌丝先端切割法纯化培养后,以形态和培养特性为基础进行了初步鉴定,发现有7株腐霉菌的形态学和培养特性一致。以其中的P3-1A为代表菌株,结合rDNA-ITS序列和β-tubulin基因序列测定和比对,将这7个菌株鉴定为Pythium heterothallicum,该菌为中国新记录,异宗配合种。通过土埋法,对玉米、番茄、黄瓜等3种作物进行了致病性测定,结果表明该腐霉菌对玉米具有致病性,可引起根腐、根尖变褐、茎基腐等症状,抑制植株生长,使植株表现不同程度的矮化,但对番茄、黄瓜未见有明显为害。

Pythium heterothallicum new to China and its pathogenicity

Pythium species were isolated by using petal baiting and tissue isolating methods from rhizosphere soils of bean,grape,cabbage and corn in Lanzhou and Zhangye,Gansu Province during September and October,2007.The Pythium colonies were taken at the colony edge for subculture and purification.The purified isolates were primarily identified based on morphology and colony characteristics.It was found that seven Pythium isolates were similar in morphology and colony.Analysis of rDNA-ITS sequence and β-tubulin gene sequence of the representative isolate P3-1A indicated that the isolates were Pythium heterothallicum,a newly recorded species in China.P.heterothallicum is heterothallic.The pathogenicity of the seven isolates were tested on corn,tomato and cucumber by using soil burying method.The results indicate that the inoculated corn showed rot root,brown and necrotic root tips,rot basal stems,growth suppression and stunting,but no obvious symptoms on tomato and cucumber.It is concluded that P.heterothallicum was pathogenic to corn but not to tomato and cucumber.