Virulence and Mating Type of Phytophthora infestans Isolates in the Czech Republic

Abstract

To evaluate the frequency and stability of the occurrence of P. infestans races and mating types in the Czech Republic, 338 monosporic isolates were collected from 31 sites in different potato-growing areas from 2012 to 2014 and in 2016. In total, 142 isolates were evaluated for virulence and race structure using the detached leaflet assay on Black's differential set, supplemented with cultivar Sarpo Mira and somatic hybrid REG 46F. With the exception of virulence for resistance genes R9 and Rpi-blb-1, all virulence genes were detected among isolates, with a predominance of genes R1, R3, R7, R10, and R11. Most isolates were virulent to five or more R-genes, with a mean virulence complexity of 7.1. Among the 38 races detected, the most commonly occurring races were 1.2.3.4.6.7.10.11 and 1.2.3.4.7.10.11. Of the 338 isolates tested by the pairing test and the cleaved amplified polymorphism sequence (CAPS) marker, 40% were of the A1 mating type and 60% were of the A2 mating type, with an A1 : A2 isolate ratio demonstrating the predominance of the A2 mating type each year of the survey.