Conditions were developed for in vitro sexual hybridization of Phytoph
thora infestans strains. The effect of culture age, illumination, medi
um composition, and treatment with enzymes on the frequency of oospore
germination was studied. The properties of F-1 hybrids and hereditary
pattern of streptomycin and blasticidin resistance, race specificity,
vegetative and sexual incompatibility, and enzyme isoforms were studi
ed.