Genetical Studies with Interspecific Crosses Between Phytophthora cinnamomi and Phytophthora parasitica

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Abstract
Two interspecific crosses between P. parasitica and P. cinnamomi resulted in the formation of oospores, but only 5% were well formed. About 5% of the normal spores germinated and gave single oospore progeny which were genetically studied. The 1st cross produced only parental type progeny, but the 2nd cross yielded heterogeneous progeny including parental type cultures and cultures with new associations of phenotypic characters. In both crosses, parental type progeny were interpreted as arising from the germination of self-fertilized oospores from the parents. Progeny with apparent recombinant phenotypes could have resulted either from interspecific hybridization or from self fertilization. Evidence of recombination was obtained in relation to mating type, pathogenicity to citrus and Persea indica, and temperature response. Presumed recombinant progeny exhibited a protein pattern similar to P. parasitica, indicating that these progeny may have resulted from self fertilization.