Occurence and distribution mating types A1 and A2 of Phytophthora infestans in eastern Estonia

Phytophthora infestans (Mont.) de Bary is one of the most serious and economically important pathogens in potato fields worldwide, including Estonia. Under favourable conditions it can destroy the whole potato haulm and cause a considerable yield loss. In Estonia, the average yield loss due to late blight can reach 20-25% and in untreated fields, even more. Without control of potato late blight it is not possible to achieve high-quality crop yield. In Estonia, fungicides are used routinely in conventional potato production, but under favourable conditions for the disease, with heavy pressure of the pathogen, protecting large areas is complicated. P. infestans isolated from potato leaves and tubers were collected from a region of Eastern Estonia during 2001-07. In total, 133 isolates were assessed for mating type. The average frequencies of mating types A1 and A2 were 59% and 38% respectively. The data indicate that in the Estonian population of P. Infestans, both mating types occur simultaneously within fields, with a potential for sexual recombination.