云南辣椒疫病的分子诊断及其病原菌群体特征研究

Molecular diagnosis and characterization of blight disease pathogen on pepper in Yunnan

对2005～2007年分离自云南省辣椒疫病的病原菌进行分子生物学鉴定,并对病原菌的群体特征进行研究。PCR特异性扩增表明,引起云南辣椒疫病的病原菌是辣椒疫霉。交配型测定显示,234个云南辣椒疫霉菌株由A1、A2和A1A2(自育型)3种交配型组成,以A2和A1A2交配型为主。其中,A2占45.3%,A1A2占43.2%,A1仅占11.5%。大部分产区3种交配型共存,在田间进行有性生殖的可能性很大。甲霜灵敏感性测定的200个菌株中,甲霜灵敏感菌株是主要菌系,占测定菌株的95.5%,中抗和抗性菌株比例较低,分别为2.0%和2.5%。抗药性菌株的出现与甲霜灵的选择压力有关。云南辣椒疫霉群体组成较为复杂,A1A2交配型可能在云南辣椒疫霉的有性生殖中起到了重要的作用,成为影响群体结构的一个重要途径。

The pathogen caused blight disease on pepper was collected from 2005 to 2007 in Yunnan, and experiments were performed to identify the pathogen by using molecular technique and characterize the pathogen by investigating mating type and metalaxyl sensitivity. The pathogen was identified as Phytophthora capsici based on the amplification of highly specific PCR. Phenotypic diversity of total 234 P. capsici isolates was characterized based on mating type and metalaxyl sensitivity. The results showed that P. capsici population collected from Yunnan was composed of A1, A2 and A1 A2 （self-fertility） mating type, in which most isolates were A2 and A1A2 with 45.3% and 43.2%, respectively. All three different mating types were detected simultaneously in most pepper production regions and even coexisted in one field, which meant that sexual reproduction might have occurred in the natural fields. Sensitivity to metalaxyl was detected among 200 isolates, of which 95.5% were sensitive and existed in all sampled pepper fields. The ratios of resistant and moderate resistant isolates were 2.0% and 2.5% respectively, which might be derived from the selection for metalaxyl. The population of P. capsici on pepper in Yunnan was diverse and it suggested that A1 A2 mating type might play an important role on sexual reproduction of P. capsici.