Genetic variation within and among populations of Fomitopsis pinicola (Basidiomycetes)

Abstract

RAPD polymorphisms were used to reveal the genetic population structure of Fomitopsis pinicola from 5 populations in southwestern Sweden with outliers in Finland and Norway. Eleven primers were used on 35 isolates. Using the Analysis of Molecular Variance (AMOVA), the total variance was divided into 3 hierarchical components: 84% within populations, 11% among regions, and 5% among populations within regions. The 3 large Swedish populations contained 95% of the variation within them. The statistical significance of these patterns was supported by permutation tests. The similarity index between all genets ranged from 0.10 to 0.72, with an average of 0.45. Genets from the same population could form more than one cluster in the neighbor‐joining analysis. Some of these clusters were also supported by parsimony jack‐knifing. This pattern is tentatively explained by establishment of spores from different basidiomata. The result of somatic incompatibility tests and RAPD markers were compared and this comparison indicated that compatible reactions do not necessarily imply genetic identity. Sampling from cut sections of infected trees revealed that multiple infections were present in a single tree and that the fungus probably infects host‐trees by basidiospores, arriving via the air. Each somatically incompatible genet characteristically monopolized only part of a resource unit. Spore trapping showed no evidence of long distance spore dispersal, but this is probably due to the limited experiment, since the genetic analysis suggested a high rate of gene flow.