CHARACTERIZATION OF A STRAIN OF CRYPHONECTRIA-PARASITICA DOUBLY INFECTED WITH HYPOVIRULENCE-ASSOCIATED DSRNA VIRUSES

To examine the effect of double infection by hypovirulence-associated viruses on the phenotype of Cryphonectria parasitica, dsRNAs from two Michigan hypovirulent isolates were cytoplasmically transferred into a common nuclear background. The coinfected strain had a dsRNA banding pattern profile that represented the sum total of the dsRNA segments of the parental strains. The douby infected strain was less virulent than either of the singly infected strains. Asexual segregation of the dsRNA viruses was followed through single-conidial isolates. The resulting asexual progeny contained one or both parental dsRNAs without any detected exchange of dsRNA segments. These findings indicate that field isolates of C. parasitica containing more than one dsRNA segment may be coinfected and that asexual segregation patterns relating dsRNA segments to hypovirulence phenotypes should be pursued before assuming the observed hypovirulence phenotype is due to a single virus.