Intersterility groups of Heterobasidion annosum in some spruce and pine stands in Byelorussia, Lithuania and Estonia

Heterobasidion annosum isolates were collected from spruce, pine and mixed stands growing on forest and former agricultural soils. Intersterility groups of the isolates were identified. Pine was attacked by the P group only and spruce mostly by the S group. Frequency of the P group on spruce was higher on old forest soils and in mixed spruce and pine stands. Based on its in vitro compatibility with the F group, the S population in Byelorussia and Lithuania is more closely related to the Finnish S population than to the Alpine S population of H. annosum.