Phenotypic and genetic characterization of Phytophthora infestans populations from Northern and Central Italy

Mating type, sensitivity to fungicides, and random amplified polymorphic DNA (RAPD) markers were used to characterize the phenotypic and genetic variations among Italian isolates of Phytophthora infestans. Thirty-five isolates of P. infestans were randomly collected from naturally infected leaves from potato and tomato fields located in the Emilia Romagna, Marche and Lombardia regions of Italy. Identification was performed by phenotypic analysis. These data were examined alongside cropping details to determine the population structure in the context of existing disease management strategies. A1 and A2 mating type isolates were present in both commercial potato and tomato crops. Assays carried out with four fungicides (metalaxyl, cymoxanil, azoxystrobin and dimethomorph) showed the sensitivity in all P. infestans populations tested. RAPD analysis showed that the isolates cluster according to the locations of their origins, and in subgroups that generally correlate with mating type and host.