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Characterization of Phytophthora cinnamomi from common walnut in Southern Europe environment

Vitale, Salvatore, Scotton, Michele, Vettraino, Anna Maria, Vannini, Andrea, Haegi, Anita, Luongo, Laura, Scarpari, Marzia, Belisario, Alessandra
Forest pathology 2019 v.49 no.1 pp. e12477
DNA, Phytophthora cinnamomi, Viburnum, analysis of variance, genetic traits, genetic variation, genotype, metalaxyl, microsatellite repeats, orchards, phenotype, phenotypic variation, provenance, temperature, virulence, walnuts, France, Italy, Southern European region
Forty‐eight isolates of Phytophthora cinnamomi obtained from common walnut were analysed according to their variability in growth at different temperatures, virulence, sensitivity to metalaxyl and in genomic DNA. Isolates were obtained from commercial common walnut orchards located in northern Italy and in southern France. Inter‐simple sequence repeat (ISSR) were analysed for the 49 isolates, 43 of which were Italian, 6 French; an isolate of the same species obtained from Viburnum spp. was used as an outgroup. 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 differentiates the group from the isolate from Viburnum spp. Correlation between phenotypic and genetic traits was not statistically significant. In conclusion, phenotypic variability like virulence seemed to be conditioned from geographic origin while the genetic variability of P. cinnamomi isolates from walnut was associated to the single genotype.