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Genetic Analysis of Host Species Specificity of Magnaporthe oryzae Isolates from Rice and Wheat

May 2006 , Volume 96 , Number  5
Pages  480 - 484

Y. Tosa , H. Tamba , K. Tanaka , and S. Mayama

Faculty of Agriculture, Graduate School of Science and Technology, Kobe University, Nada, Kobe 657-8501, Japan

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Accepted for publication 23 December 2005.

A Triticum isolate (pathogenic on wheat) of Magnaporthe oryzae was crossed with an Oryza isolate (pathogenic on rice) to elucidate mechanisms of their parasitic specificity on wheat. When the pathogenicity of their F 1 cultures (hybrids between a Triticum isolate and an Oryza isolate) was tested on wheat, avirulent and virulent cultures segregated in a 7:1 ratio. This result suggests that three loci are involved in avirulence of the Oryza isolate on wheat. One of the three loci conditioned papilla formation, whereas the others conditioned the hypersensitive reaction. Allelism tests revealed that the locus conditioning papilla formation is Pwt2 while one of the two loci conditioning the hypersensitive reaction is Pwt1. The other locus conditioning the hypersensitive reaction was different from any other known loci and, therefore, was designated as Pwt5.

Additional keywords: Pyricularia.

© 2006 The American Phytopathological Society