IDENTIFICATION OF VEGETATIVE COMPATIBILITY TYPES OF CRYPHONECTRIA PARASITICA AND HYPOVIRULENCE OCCURRENCE IN CASTANEA SATIVA IN TOSCO-ROMAGNOLO APENNINE

Castanea sativa, one of the most precious forest trees in Apennines, is affected by chestnut blight caused by Cryphonectria parasitica. Since 1938, when the pathogen was observed for the first time in Italy, several field surveys have been carried out in chestnut stands. This work reports the results obtained during a recent survey of 9 chestnut populations distributed in three Tosco-Romagnolo Apennine valleys. Two hundred and seventeen isolates of C. parasitica were obtained from trees showing different stages of decline and three morphotypes: orange, intermediate and white, were detected. Sixteen isolates (7%) showed orange pigmentation suggesting virulence, while 201 isolates (93%) showed intermediate and white morphology. Identification and mapping of the vegetative compatibility (vc) types of 82 C. parasitica isolates was carried out and three vc types were identified by means of tester isolates. Our results showed that EU-2 was the dominant vc type reaching a percentage of 47%, while the EU-5 and EU-1 were 18% and 14%, respectively. In addition, the 21% of isolates was incompatible with the examined testers. The results revealed a low diversity in vc types and the occurrence of natural hypovirulence in three different valleys supporting the feasibility of successful application of biological control on the Tosco-Romagnolo Apennine. Additionally the occurrence of Cryphonectria hypovirus 1 (CHV-1) in the selected panel of 82 C. parasitica isolates was determined using a specific TaqMan Real-Time RT-PCR assay. More than 20% of tested samples resulted infect by CHV-1 and natural hypovirulence of fungal isolates was therefore investigated.