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Interaction of Genes Controlling Avirulence/Virulence of Magnaporthe grisea on Rice Cultivar Katy. G. W. Lau,Department of Bacteriology, 1630 Linden Dr., University of Wisconsin, Madison 53706, Current address: Department of Biological Sciences, Lily Hall of Life Sciences, Purdue University, West Lafayette, IN 47907; C. T. Chao(2), and A. H. Ellingboe(3). (2)(3)Plant Breeding and Plant Genetics Program, and Departments of Plant Pathology and Genetics, respectively, 1630 Linden Dr., University of Wisconsin, Madison 53706. Phytopathology 83:375-382. Accepted for publication 22 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-375.

Lines of Magnaporthe grisea have been developed that are sexually competent and that differ in their avirulence/virulence on one rice cultivar. Two sibling isolates, 70-14 and 70-6, were each virulent on 10 rice cultivars. On rice cultivar Katy, 70-14 was avirulent, and 70-6 was virulent. The 70-14 70-6 cross produced 26 avirulent progenies and 28 virulent progenies, which suggested segregation of two alleles at one locus. Intercrosses among the progenies as well as backcrosses and test crosses suggested two avirulence genes and two corresponding suppressors were interacting to control avirulence/virulence on Katy. These avirulence genes and suppressors were designated P11 and P12 and S11 and S12, respectively. The proposed genotypes of all the isolates used in this study are given. In addition, P12, mating type MAT1, and S12 were loosely linked.

Additional keywords: avirulence/virulence genes, cultivar specificity, linkage, rice blast.