NUMBER OF HETEROBASIDION-ANNOSUM VEGETATIVE COMPATIBILITY GROUPS IN ROOTS OF BASIDIOSPORE-INFECTED STUMPS

Heterobasidion annosum was isolated from colonized parts of Sitka spru ce stumps in Dundeugh Forest, Scotland and amabilis fir stumps in Rive r Jordan, Vancouver Island, British Columbia. Isolates from each stump were paired in all combinations on malt extract agar and their intera ctions were scored according to established criteria. As many as ten v egetative compatibility (VC) groups were detected among isolates from the roots of a single stump. In four stumps that were intensively stud ied, about one-half of the VC groups in the roots were not detected in the upper part of the stump. Transfer of VC groups of H. annosum from stump roots to tree roots was observed.