VIEW ARTICLE

Identification of Strains and Inheritance of Pathogenicity in Phytophthora capsici. F. J. Polach, Department of Plant Pathology, University of California, Davis 95616, Present address of senior author: Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, New York 14456; R. K. Webster, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 62:20-26. Accepted for publication 12 July 1971. DOI: 10.1094/Phyto-62-20.

Fourteen distinct pathogenic strains were identified among 23 diverse isolates of Phytophthora capsici when tested on tomato, eggplant, squash, watermelon, sugar pumpkin, and selected lines of pepper. No correlations between pathogenicity to a specific host and the mating reaction of a given isolate were found. Factors controlling pathogenicity were further characterized by genetic studies on 391 single oospore progeny. Recombination between factors conditioning pathogenicity and mating group occurred, indicating that pathogenicity to the various hosts is controlled by a separate gene or gene system for each host. Pathogenicity to pepper is controlled by at least two genes. Genetic ratios obtained did not allow a determination of ploidy of P. capsici because of the low percentage of oospore germination and the possibility that some of the progeny were derived from selfed oospores of one or the other of the parent isolates.