Lithuanian Populations of Phytophthora infestans Revealed a High Phenotypic Diversity

This is the first characterisation of Lithuanian populations of Phytophthora infestans with mating type and virulence on a differential set of 11 R genes of Solanum demissum . The sensitivity to metalaxyl was also determined. In 2010–2012, 93 Phytophthora infestans isolates, collected from all over Lithuania, showed quite high and stable frequency of A2 mating type. On 45% of all studied potato fields, both mating types were recorded, suggesting sexual reproduction of P. infestans and possible oospore production in Lithuanian potato fields. Fourteen metalaxyl-resistant isolates were found among 71 isolates in the current study period, and sensitive isolates prevailed in all three years. Amongst the studied 70 isolates, 38 avirulence pathotypes were found. The Lithuanian race structure was highly diverse and complex (the average number of missing avirulence factors per isolate was 7.2). Most pathotypes were unique, appearing only once, and the four most common pathotypes comprised only 34% of the population.