小麦白粉菌高密度遗传图谱定位AvrPm5b和AvrPm30及候选基因分析

Wheat powdery mildew, caused by Blumeria graminis f.sp. tritici (Bgt), is an important threat to wheat production in China. Monitoring the virulence and diversity of Bgt population can guide the spatio-temporal deployment of R genes in the field. The genetic mapping and cloning of avirulence gene (Avr gene) is prerequisite and foundation of monitoring Bgt population, and critical for understanding pathogenesis of Bgt as well as interaction between Bgt and wheat. The virulence and diversity of Bgt in wheat-growing regions have been monitored and 100 isolates were selected for genome sequencing and phenotype assay on wheat differentials. Isolates E21 and HB-24 was virulent and avirulent respectively on differentials carrying Pm5b and Pm30, and cross between the two strains had been performed and produced a suitable mapping population with 99 progenies. This project will do whole genome re-sequencing of these progenies and generate SNPs markers to construct the high-density linkage map. The molecular marker have close linkage to AvrPm5b and AvrPm30 will be acquired, and combined with the transcriptome data of virulent and avirulent strains from the fields for bioinformatic analysis to identify candidate genes of AvrPm5b and AvrPm30. The construction of high-density linkage map provide useful platform to genetic mapping other Avr genes of Bgt, and will help us to clone these two Avr genes.

小麦白粉菌引起的白粉病严重影响小麦生产安全。白粉菌群体毒性结构分析有利于抗病品种合理布局和延长使用寿命。无毒基因定位与克隆，是从分子水平监测白粉菌群体毒性结构、明晰其变异动态、合理布局抗病品种的前提和基础，更对研究病原菌致病机理、与寄主互作等方面具重要意义。在监测全国主产麦区白粉菌毒性结构、对致病型有差异100个自然群体菌株测序和分析基础上，选择对Pm5b和Pm30毒性菌株E21和无毒菌株HB-24为亲本，以获得的99个后代菌株为遗传群体。拟对后代菌株进行全基因组重测序，构建白粉菌高密度SNP标记遗传图谱，结合表型定位获得AvrPm5b和AvrPm30紧密连锁标记，参考已发表小麦白粉菌全基因组序列，结合自然群体转录组数据，获得无毒基因候选基因。小麦白粉菌高密度遗传图谱的构建、AvrPm5b和AvrPm30定位及候选基因的确定，可为定位白粉菌其它无毒基因及克隆相关无毒基因奠定基础。

小麦白粉菌引起的白粉病严重影响小麦生产安全。白粉菌群体毒性结构分析有利于抗病品种合理布局和延长使用寿命。无毒基因定位与克隆，是从分子水平监测白粉菌群体毒性结构、明晰其变异动态、合理布局抗病品种的前提和基础，更对研究病原菌致病机理、与寄主互作等方面具重要意义。本研究以对Pm5b有毒性的小麦白粉菌菌株E21和无毒菌株HB-24为亲本，以获得的128个后代菌株为遗传群体（与申请时比增加29个后代菌株）。对亲本及128个后代菌株进行Illumina Hiseq2500/4000全基因组重测序，利用过滤后20766个SNP标记，构建小麦白粉菌高密度遗传图谱，该图谱包含11个连锁群，总长度9265cM。最终无毒基因AvrPm5b被定位在标记Bgt_chr-07-0864175至Bgt_chr-07-1156995之间292.82kb的候选区域，候选区域包含12个候选基因。最终根据亲本与后代菌株的表型（对Pm5b毒性/无毒性）与基因型对应关系，筛选出4个候选基因：Bgt-20201、Bgt-50266、Bgt-50267和BgtE-5845。这4个候选基因在无毒性菌株和毒性菌株中表现出PAV（Present/Absent Variation）差异。对4个候选基因分别分析，分别有90%到93%的后代菌株是亲本表型对应的基因型类型。下一步计划将小麦白粉菌无毒基因AvrPm5b这4个候选基因将与小麦Pm5b抗性基因进行烟草上外源表达互作，以最终克隆AvrPm5b。