Identification and cloning of genes conditioning species-specific parasitism of Magnaporthe oryzae

为了阐明稻瘟病属植物物种特异性的遗传机制，我们将一个小麦分离物与一个尾草属分离物、一个稻瘟病属分离物和一个稻瘟病属分离物进行杂交。利用这些杂交获得的F_1后代，我们鉴定了PWT1、PWT2（尾草属分离物对小麦的调节毒力）、PWT3、PWT4 （Avena分离物对小麦的调节毒力）、PWT5 （Oryza分离物对小麦的调节毒力）、PFM1、PFM2 （Triticum分离物对谷子的调节毒力）和PAT1 （Triticum分离物对燕麦的调节毒力）。我们还发现了一个与PWT4相对应的抗性基因，并将其命名为Rwt4。Rwt4与PWT4呈一一对应关系，表明小麦分离物对小麦的物种特异性受基因间相互作用的制约。从这些无毒基因中，选择PWT1、PWT4和PAT1作为分子克隆的靶点。通过散装分离分析，我们发现了与PWT1、PWT4和PAT1密切相关的分子标记。

To clarify genetic mechanisms of plant-species specificity of Magnaporthe oryzae, we crossed a Triticum isolate with a Setaria isolate, an Avena isolate, and an Oryza isolate. Using the F_1 progenies derived from these crosses, we identified PWT1, PWT2 (conditioning avirulence of the Setaria isolate on wheat), PWT3, PWT4 (conditioning avirulence of the Avena isolate on wheat), PWT5 (conditioning avirulence of the Oryza isolate on wheat), PFM1, PFM2 (conditioning avirulence of the Triticum isolate on foxtail millet), and PAT1 (conditioning avirulence of the Triticum isolate on oat). We also identified a resistance gene corresponding to PWT4, and designated it as Rwt4. Rwt4 corresponded to PWT4 in a one-to-one manner, suggesting that the plant species specificity of the Triticum/Avena isolates on wheat is conditioned by gene-for-gene interactions. From these avirulence genes, PWT1, PWT4, and PAT1 were chosen as targets for molecular cloning. Using bulked segregant analysis, we found molecular markers that are closely linked to PWT1, PWT4 and PAT1.