Phenotypic and genotypic characterization of Italian Phytophthora infestans isolates

Phytophthora infestans (Mont.) de Bary causes late blight of potato. After the 1970s, several changes have occurred in the European P. infestans population, frequently associated with an increased virulence. While the genotypic and phenotypic diversity of P. infestans has been studied in-depth in northern and central Europe, only a few reports are available regarding Italian isolates, mainly based on phenotypic traits. We report data of phenotypic and genotypic characteristics of isolates collected from infected potato and tomato plants in different Italian regions in 2006‒2008. A prevalence of the A1 mating type and a majority of metalaxyl-resistant isolates were found. Tomato-derived isolates showed fungicide sensitivity, confirming previous reports. One of the isolates showed the rare IIb mitochondrial DNA haplotype. Genetic analyses of the single-sequence repeats (SSRs) and of the internal transcribed spacers gave similar results, although SSRs gave the best discrimination of genotypes