SPREAD OF S-GROUP AND P-GROUP ISOLATES OF HETEROBASIDION-ANNOSUM WITHIN AND AMONG PICEA-ABIES TREES IN CENTRAL LITHUANIA

Spread of Heterobasidion annosum (Fr.) Bref. was investigated in a 60- year-old Norway spruce (Picea abies (L.) Karst.) stand in central Lith uania. Of the 375 trees sampled, H. annosum was isolated from 85 (22.7 %). Forty nine (56.3%) of the isolates belonged to the S group and 38 (43.7%) to the P group. Among the S-group isolates, 35 genets occupied 49 trees (1.4 trees per genet on average). In the P group, 24 genets were detected in 37 trees (1.5 trees per genet on average). The larges t S and P genets were 21 and 20 m in diameter, respectively. The S gro up spread was more extensive within stems than for the P group; mean l ength of the decay column for S-group isolates was 459 +/- 159 cm (mea n +/- SD), and it was 327 +/- 101 cm for P-group isolates (p = 0.0001) . Average stump area affected by decay was 56 +/- 15% for the S group, and 47 +/- 16% for the P group (p = 0.016). This is the first publish ed field data on intersterility group related difference in decay exte nsion in tree stems. The S group is better adapted than the P group to growth in Norway spruce wood.