TRANSMISSION OF HYPOVIRULENCE AGENTS AMONG SOME CRYPHONECTRIA-PARASITICA STRAINS FROM ITALY

Six hypovirulent (H) strains of Cryphonectria parasitica collected in Italy were tested for dsRNA content, virulence, and conversion ability . Nine converts were also checked for dsRNA. In inoculation trials, H and converted (C) strains showed reduced pathogenicity. Most H and C s trains were able to convert strains from various v-c groups. DsRNA ban ding patterns were similar in five of the H strains and in their conve rts, while the last one and its converts showed no evidence of dsRNA. The broad conversion ability of H strains seems to be responsible for the natural recovery of Italian chestnut trees.