河北省番茄上致病疫霉Phytophthora infestans群体结构的分析

番茄晚疫病是河北省番茄生产上最具毁灭性的病害之一,对引起该病害的致病疫霉群体结构进行分析有利于病害的防治。利用对峙培养法和菌落直径法对2007-2008年采自河北省保定、沧州和唐山分离自番茄的49个致病疫霉菌株进行了交配型和甲霜灵抗性的表型测定,结果表明该群体所有菌株均为A1交配型,以甲霜灵敏感菌株为主,抗性菌株仅7株。利用聚合酶链式反应-限制性片段长度多态性(PCR-RFLP)、简单序列重复(SSR)和扩增片段长度多态性(AFLP)等分子技术对该群体的基因型进行了分析,结果表明供试菌株线粒体基因型均为Ia型,共鉴定出了Ⅰ、Ⅱ和Ⅲ3种SSR基因型,AFLP聚类分析在相似系数0.87时可以形成α、β和γ等3个不同的分支。河北省所有番茄上致病疫霉菌株均分布在α分支上,该分支又可进一步分为7个亚分支。AFLP亚分支与甲霜灵抗性和地理来源均无明显相关性,但Ⅱ型SSR与甲霜灵抗性和地理来源有明显的相关性。综合表型和基因型数据说明河北省番茄上致病疫霉群体结构比较单一,遗传多样性程度较低。

Population structure of Phytophthora infestans on tomato in Hebei Province

Tomato late blight is one of the most devastating diseases in tomato production in Hebei Province.The study of the population structure of Phytophthora infestans on tomato is contributive to the control of the disease.The phenotypes of 49 isolates collected in Baoding,Cangzhou and Tangshan cities of Hebei Province during 2007 and 2008 were investigated for mating types and metalaxyl resistance respectively by means of dual culture with A1 and A2 testers on rye plates and radical growth assay on fungicide-amended media in vitro.The results show that all the tested isolates were A1 mating type,their majorities were metalaxyl-sensitive and only seven isolates were metalaxyl-resistant.The genotypes were also assessed for mitochondrial DNA haplotypes with polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP),simple sequence repeats(SSR) and amplified fragment length polymorphism(AFLP).Only one DNA haplotype(Ia) and three SSR genotypes(type Ⅰ,type Ⅱ and type Ⅲ) were determined in this study.However,three AFLP clades(α,β and γ) were formed at a genetic similarity value of 0.87 and all isolates of tomato Phytophthora infestans from Hebei were included in α clade,which were further divided into seven sub-clades.The seven AFLP sub-clades were not associated with metalaxyl resistance and geographical origin,however,type Ⅱ SSR genotype was correlative to metalaxyl resistance and geographical origin.The phenotypic and genotypic data indicate that the population structure of Phytophthora infestans from tomato in Hebei Province was lower in genetic diversity.