Increased genotypic diversity via migration and possible occurrence of sexual reproduction of Phytophthora infestans in Poland.

Genetic changes in populations of Phytophthora infestans in Poland were determined by analyzing 247 isolates collected from 1985 through 1991. All isolates collected from 1985 through 1987 were Al mating type and consisted of a single clonal lineage based on allozyme and DNA fingerprint analyses. The appearance of new genotypes in Poland, presumably due to migration, was first detected in 1988 with the identification of the A2 mating type, three allozyme, and a number of DNA fingerprint alleles that had not been detected previously. This migration resulted in dramatic changes. Gene and genotype diversity and the frequency of uniquely detected genotypes all increased beginning in 1988, and reached a peak in 1990 [...]