Caracterización morfológica y molecular de las poblaciones de "Cryphonectria parasitica" en castaños de Galicia

Abstract

Chestnut blight caused by Cryphonectria parasitica is a fungal disease widely spread in chestnut stands all over the world. At present, the only feasible perspectives for its control are based on the knowledge of the populations present in the affected stands and the use of hypovirulent strains. The biology of C. parasitica populations naturally occurring in chestnut stands in Lugo and Ourense provinces was then studied so as to determine the diversity of vegetative compatibility (vc) and mating types, as well as the occurrence of hypovirulent strains. A total of 610 isolates were obtained. Only 4 isolates, from Lugo province, showed the presence of ARNbc, characteristic of hypovirulent strains. Molecular characterization of hypovirus proved all hypovirulent strains belonged to Cryphonectria hypovirus 1 (CHV1-E). The diversity of vegetative compatibility was very low. Nine vc types were found, five of them occurring in both provinces. Four types were compatible with the known European testers and the others were unreported vc types named E1, E2, E5, E6 and E7. Dominant vc types in both populations were E1, E2 and E5, being detected in 97% of the isolates. Four hypovirulent strains were found: two compatible with vc type E1, one with E2 and other with E5. The study of mating types showed that idiomorph MAT-1 was dominant in both populations. Reproduction mainly asexual, together with the low diversity of vegetative compatibility types and the presence of hypovirulent strains compatible with dominant vc types, are factors favouring the application of a biological control program against chestnut blight in chestnut stands in Lugo and Ourense provinces.