Hosts and distribution of the intersterility groups of Heterobasidion annosum in the highlands of Greece

The intersterility groups of 127 pure cultures of H. annosum collected from different host trees in 12 mountain areas In Greece were identified. The F group commonly caused butt rot on the fir species Abies cephalonica and Abies borisii regis. It was the only type of H. annosum found in pure fir forests. The P group caused serious root rot in Pinus sylvestris stands in north-eastern Greece. In more southern mountain areas it often colonized stumps of Pinus nigra bur seldom killed this tree species. The S group was found in natural forests of Picea abies in northern Greece, causing butt rot of spruce. In mixed forests, the intersterility groups of H. annosum were found relatively often in stumps of tree species other than their main hosts, although some host preference seemed to occur also in stump colonization.