The detection of nonhybrid, trisomic, and triploid offspring in sexual progeny of a mating of Phytophthora infestans

Eighty single-oospore offspring of Phytophthora infestans from a mating of isolates, which had previously been analyzed for segregation of avirulence/ virulence, were assessed for the inheritance of 20 RFLP markers. Three offs pring were triploid; they inherited three alleles at all loci where this co uld be detected and when heterozygous, showed unequal intensities of hybrid ization with most probes. Twenty-four offspring were trisomic, as each had three doses of one or a few markers, evident from their inheritance of thre e alleles or from unequal hybridization to one probe. Coinheritance of the extra allele(s) and mitochondrial haplotype in the majority of trisomic off spring suggested that meiosis in oogonia was more aberrant than in antherid ia. Linkage analysis was performed on 50 offspring, which were assumed to b e euploid; six small linkage groups were detected and several avirulence lo ci were found to be linked. The origins of aberrant offspring are discussed , (C) 1999 Academic Press.