INTRASPECIFIC GENETIC-VARIATION IN HETEROBASIDION-ANNOSUM REVEALED BY AMPLIFICATION OF MINISATELLITE DNA

DNA from 124 strains of Heterobasidion annosum was amplified using the core sequence of the M13 minisatellite region as primer. The strains were derived from 11 S-, 8 P- and 1 F-intersterility group populations originating in Scandinavia, Germany and Italy. Following electrophoresis the banding patterns of all isolates were compared and 23 fragments were scored. Average band-sharing indices (ABSI) were used to compare genetic diversity within and between populations. Genetic similarity of populations decreased with increasing geographical distance in the S group. In both the S and P intersterility groups, ABSI values were higher within than among populations (70.3 +/- 2.3 S.D. and 66.4 +/- 2.2, respectively in the S group and 77.0 +/- 2.3 and 75.0 +/- 2.4, respectively in the P group) indicating local differentiation. The higher values in the P than in the S group indicate that the P group is less variable. ABSI was much lower between S and P group populations (49.2 +/- 2.5) than within either group. This result demonstrates the large divergence between these two intersterility groups. In the F population ABSI was higher (68 +/- 3.1) than for the comparisons with the S- (50.1 +/- 1.6) and P-groups (44.0 +/- 2.4). By using discriminant analysis, the agreement between geographical population affiliation and that inferred from banding patterns of amplified DNA was 20.8% within the S group, and 14.9% within the P group. Chi-square test of the discriminant analysis indicated regional differentiation in the S but not in the P intersterility group. The agreement between methods was 98.4% when strains were classified to intersterility group by pairing tests or amplified DNA profiles. Results are consistent with a high degree of exchange between populations of the same intersterility group but low exchange between intersterility groups.