Date of Graduation
Davis College of Agriculture, Natural Resources and Design
Applied and Environmental Biology
William L. MacDonald.
In 1994 and 1995, Cryphonectria parasitica isolates singly or doubly infected with hypoviruses in the CHV3 genus, and lacking distinctive morphological abnormalities, were recovered near plots formerly used to release hypoviruses. This study tested the hypothesis that North American hypoviruses are evolving decreased virulence, and investigated hypovirus interactions affecting virulence in double-infections. Families of single conidial progeny (SCP), differing in infection status, and derived from six recovered, three release, and three comparison isolates were tested in three field experiments. All release isolates and four recovered isolates were debilitated by their CHV3-gh2-type hypoviruses. CHV3-sr2-type hypoviruses never caused debilitation. In family SG3-2 the two hypoviruses were less virulent together than either alone, a negative interaction. Positive interaction was observed in family P1-3-1-3, and masking of the weaker hypovirus by the stronger was seen in family SG7-1. This study provided only limited support for the evolution of decreased hypovirus virulence in North American.
Chaloux, Paul Henry, "Virulence of cryphonectria hypoviruses from previous release sites" (2000). Graduate Theses, Dissertations, and Problem Reports. 1118.