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Genetics

Genetic Evidence for Diploidy in Phytophthora megasperma var. sojae. Margaret Long, Staff Research Associate, Department of Plant Pathology, University of California, Riverside, CA 92502; N. T. Keen, Associate Professor, Department of Plant Pathology, University of California, Riverside, CA 92502. Phytopathology 67:675-677. Accepted for publication 17 November 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-675.

Several met + pur heterokaryons constructed from a methionine- and a purine-requiring mutant of the homothallic fungus Phytophthora megasperma var. sojae produced only parental auxotrophic and recombinant prototrophic oospores when selfed. Oospore progeny obtained from selfing first-generation prototrophic recombinant progeny segregated into four classes as expected in a vegetatively diploid organism, but a 9:3:3:1 ratio was not obtained. Deviation from the classical ratio appeared to reflect inferior germination and colony establishment by the recombinant auxotrophic progeny.