Analysis of host species specificity of Magnaporthe grisea toward wheat using a genetic cross between isolates from wheat and foxtail millet

A genetic cross was performed between a Setaria isolate (pathogenic on foxt ail millet) and a Triticum isolate (pathogenic on wheat) of Magnaporthe gri sea to elucidate genetic mechanisms of its specific parasitism toward wheat . A total of 80 F-1 progenies were obtained from 10 mature asci containing 8 ascospores. Lesions on wheat leaves produced by the Fl progenies were cla ssified into four types, which segregated in a 1:1:1:1 ratio. This result s uggested that the pathogenicity of the F-1 population on wheat was controll ed by two genes located at different loci. This idea was supported by backc ross analyses. We designated these loci as Pwt1 and Pwt2. Cytological analy ses revealed that Pwt1 and Pwt2 were mainly associated with the hypersensit ive reaction and papilla formation, respectively.