Transmission of Cryphonectria hypovirus to protect chestnut trees from chestnut blight disease

Abstract

The effects of hypovirus transmission in Cryphonectria parasitica were tested by co-culture of Cryphonectria hypovirus (CHV) donor strains with recipient strains. Virulence of the CHV-containing strains was determined by inoculation into cut chestnut stems in the laboratory and into chestnut trees in the field. The viral double-stranded RNA (dsRNA) transmission rate between C. parasitica strains on agar medium in the laboratory ranged from 0% to 100% depending upon the strain combination. The results of our laboratory and field inoculation experiments indicated that the virulence of six laboratory-infected hypovirulent strains (LH), 12 dsRNA donor strains (H), six pairs of hypovirulent strains (H) mixed with wild-type strains (V), and six pairs of laboratory-infected hypovirulent strains (LH) mixed with dsRNA free isolates derived from dsRNA-containing strains (LV) was lower than that of virulent recipient strains (V) alone. One year after co-inoculation in the field, most wild-type strains were converted by the hypovirulent strains, even those strains that were not converted in the laboratory. The results suggest that there is better than expected potential for biological control of chestnut blight disease.