STRUCTURE OF COLLYBIA-FUSIPES POPULATIONS IN 2 INFECTED OAK STANDS

Collybia fusipes is the cause of a root rot of oak trees. We studied t he structure of C. fusipes populations in two infected oak stands by u sing somatic incompatibility and DNA amplification. Isolates were obta ined from different oak root systems or from within the same root syst em and somatic incompatibility groups (SIG) were identified. Many smal l SIGs that seldom encompassed more than one root system were present in both stands. More than one SIG was usually present on an individual root system: there were 3.1+/-1.3 SIGs on the pedunculate oaks and 2. 2+/-0.6 on the red oaks. The largest SIG contained more than 70% of th e isolates obtained from the root system of 14 of the 20 trees studied . Isolates that belonged to the same SIG usually had the same ribosoma l intergenic spacer. It is concluded that C. fusipes spreads poorly fr om tree to tree by vegetative means.