Characterization of Genotype and Mating Type in European Isolates of Plasmopara viticola

A total of 54 single sporangiophore isolates of Plasmopara viticola from seven regions in four European countries were examined for mating type and genotypic characteristics, using amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSR, microsatellites) markers. Grape leaf discs were co-inoculated with sporangia of randomly selected single sporangiophore isolates. Based on oospore production, four fertile isolates were selected: two were defined as P1 and two as P2 mating types. This procedure was necessary because no reference isolates were available. Among the 54 isolates, 33 belonged to the P1 and 21 to the P2 mating type. AFLP and SSR analyses allocated a distinctive genotype to almost each isolate, thus reflecting a high genetic diversity among the isolates (heterozygosity index He 0.59–0.80). AFLP clustering was observed among isolates collected from the same region, whereas no clustering occurred with SSR. This study provides defined P1 and P2 isolates which will allow future genetic investigations on the inheritance of phenotypic traits in P. viticola such as the sensitivity to fungicides