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Genetics of Virulence in Cochliobolus sativus and Resistance in Barley

November 1997 , Volume 87 , Number  11
Pages  1,140 - 1,143

Majda Valjavec-Gratian and Brian J. Steffenson

Department of Plant Pathology, North Dakota State University, Fargo 58105

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Accepted for publication 18 August 1997.

Spot blotch, caused by Cochliobolus sativus, is one of the most common foliar diseases of barley in the upper midwest region of the United States. To examine the genetics of host-specific virulence in C. sativus, a cross was made between isolate ND90Pr (which exhibits high virulence on barley genotype Bowman and low virulence on genotype ND 5883) and ND93-1 (which exhibits low virulence on both genotypes). Ascospore progeny segregated 48:55 for low virulence/high virulence on Bowman, indicating the presence of a single virulence gene in isolate ND90Pr. To complement the study of host-specific virulence in the pathogen, an experiment also was conducted on the genetics of specific resistance in the host. Progeny from a Bowman/ND 5883 cross were evaluated for their infection responses (IRs) to isolate ND90Pr at the seedling stage. The F2 population segregated 1:3 for low IRs (resistant)/high IRs (susceptible), indicating the presence of a single resistance gene in genotype ND 5883. This result was confirmed in the F3 generation, as a 1:2:1 ratio was found for homozygous resistant, segregating, and homozygous susceptible families, respectively. The data from this study demonstrate that both virulence in the pathogen and resistance in the host are under monogenic control in this specific host genotype/fungal isolate combination.

Additional keywords: Hordeum vulgare.

© 1997 The American Phytopathological Society