Characterization of Phytophthora cinnamomi from common walnut in Southern Europe environment. Phytophthora cinnamomi from common walnut

Isolates of Phytophthora cinnamomi obtained from common walnut were analyzed according to their variability in growth at different temperatures, virulence, sensitivity to metalaxyl and in genomic DNA. Isolates were obtained from common walnut commercial orchards located in northern Italy and in southern FranceInter-simple-sequence-repeat (ISSR) were completed for the 49 isolates, 43 of which were Italian, 6 French. ANOVA on phenotypic characters showed a significant impact of the geographic location of the orchard on isolate variability in terms of reaction to temperatures and aggressiveness. In turn, clustering obtained with UPGMA analysis on genetic data was almost exclusively dependant on isolate variability, nevertheless the 48 isolates seem to share a common variability that differentiate the group from the isolate from viburnum. Correlation between phenotypic and genetic traits was not statistically significant. In conclusion, phenotypic variability like virulence seemed to be conditioned from geographic origin while genetic variability of P. cinnamomi isolates from walnut was associated to the single genotype.