OCCURRENCE AND DIVERSITY OF VEGETATIVE COMPATIBILITY TYPES OF CRYPHONECTRIA PARASITICA IN GALICIA (NW SPAIN)

Cryphonectria parasitica, the causal agent of chestnut blight, is widely spread in the north of the Iberian Penisula, causing significant economic losses. Fungal isolates with low virulence, characterized by white colonies in culture and the presence of double-stranded RNA, have been found in Europe and used to treat chestnut cankers by transmitting hypovirulence to virulent strains. The occurrence and diversity of vegetative compatibility (vc) types of C. parasitica was estimated in 916 chestnut tree stands located in four provinces of Galicia (NW Spain) during 2002 and 2003. A total of 198 isolates of C. parasitica were obtained from 466 trees showing typical canker symptoms. Eight vc types were identified, three of them with only one isolate each. vc type A was the largest with 138 isolates. The highest diversity of vc types was found in the province of A Coruña. Only one group, named vc type E, was compatible with a European tester, EU-1. Double-stranded RNA was obtained from two isolates, which showed morphological and growth characteristics suggestive of hypovirulence. Results obtained with this study will facilitate biological control implementation in Galicia.