Genetic relatedness among strains of Heterobasidion annosum as detected by random amplified polymorphic DNA markers

Heterobasidion annosum, the casual agent of root and butt rots of trees is one of the most important plant pathogens in temperate coniferous regions of the world. It is comprised of several intersterility groups with different host preferences. Of the H. annosum isolates from various geographical regions belonging to various intersterility groups, 36 showed group-specific banding patterns in RAPD assay. More polymorphisms were found within the S- and F-group isolates than in the P group. Genetic similarities among the isolates were determined by UPGMA clustering revealing the presence of four major clusters: P, S, F, and the North American S. The P group was the most distinctive of all the other groups, while the European S and F and the North American S were more closely related. The P group showed only 20% similarity to the other groups and may be referred to as a subspecies. The North American S group was separate from the European S group. The potential influence of the historical spread of coniferous trees in the isolate genetic differentiation in Europe is discussed.