宁夏固原致病疫霉群体结构特征

Population structure of Phytophthora infestans from Ningxia

为揭示宁夏固原致病疫霉群体遗传结构,用对峙培养法和菌落直径法测定致病疫霉的交配型和甲霜灵抗性,利用限制性片段长度多态性聚合酶链反应(PCR-RFLP)技术检测致病疫霉线粒体DNA单倍型,并采用简单重复序列(SSR)和扩增片段长度多态性(AFLP)技术确定致病疫霉群体的基因型。在94株供试菌株中,发现了1株A1交配型、86株A2交配型及7株自育型菌株,全部为甲霜灵抗性菌株。菌株的线粒体单倍型均为Ⅰa型,共鉴定出2种SSR基因型,Ⅰ型占绝对优势。AFLP聚类分析显示,在相似系数0.68时分成α和β两组,宁夏固原菌株全部聚在β组。研究表明,宁夏固原致病疫霉群体结构比较单一、遗传多样性水平较低。

The population genetic structure of Phytophthora infestans collected from Guyuan of Ningxia Hui Autonomous Region was revealed by the combination of phenotypes and genotypes. The phenotypes of P. infestans i.e. mating types and metalaxyl resistance were investigated by means of dual culture with A1 and 3,2 testers on rye plates and radical growth assay on fungicide-amended media in vitro, respec- tively. Mitochondrial DNA haplotypes of isolates of P. infestans were detected with restriction fragment length polymorphism and polymerase chain reaction （PCR-RFLP）. Genotypes of genomic total DNA of P. infestans were examined by simple sequence repeats （SSR） and amplified fragment length polymor- phism （AFLP）. Of tested 94 isolates, only one was A1, 86 ones were A2, and the seven ones were self- fertile. Nevertheless, all tested isolates were metalaxyl-resistant. Only one mitochondrial DNA haplotype （ I a） and two SSR genotypes （ named as types I and II ） were determined among population, one （ i. e. type I ） of which was absolute predominance. Then, two AFLP clades （i. e. α and β clade） were formed at a genetic similarity value of 0. 68 and all isolates of P. infestans from Guyuan of Ningxia were included in β clade. All data indicated that the population structure of P. infestans from Guyuan was very simple and the level of genetic diversity was much less.