Heterobasidion annosum group S identified in north‐eastern China

Summary Samples of Heterobasidion annosum were collected in two stands of mixed forest in Changbaishan Nature Reserve in north‐eastern China. Pure cultures were isolated from 15 specimens growing on Abies, Picea, Pinus and Populus. Mating tests showed that all these collections belong to the S inter‐sterility group. The compatibility of Chinese homokaryons with S homokaryons from Europe was 100%. Clamp connections appeared almost equally in both strains of each pairing, and no distinct demarcation line formed in the pairings. The mating frequency of Chinese isolates with the European F group was also high, approximately 94%. These matings, however, were usually unilateral and a more or less distinct demarcation line was present in most of the pairings. The Chinese isolates were completely intersterile with the European P group. The S group of H. annosum in north‐eastern China appears to have similar morphology and ecology as in Europe. It is common on Abies and Picea, but is not a serious pathogen in the pristine forests of north‐eastern China.