Distribution of hypovirulent strains of Cryphonectria parasitica in Tuscany (Italy) as influenced by climatic-environmental factors

During the 2005 phytopathological forest survey of the Tuscany Region, named META (Regione Toscana 2008a), the occurrence of Cryphonectria parasitica, responsible of the chestnut blight, was registered on all of the 63 monitoring areas and on about 90% of the trees. The hypovirulent strains of the pathogen were mostly prevalent (about twice) then virulent ones, excluding some areas near the Apennines. Generally hypovirulent strains were present in sites showing high values of solar radiation, where the dsRNA transfer from mycelia resulted easier, in respect to chilly sites (p < 0.05). The analysis offers a chance to predict the spreading of hypovirulent strains and organize sanitary operations in chestnut stands.