Genetic differentiation between European and North American populations of Phlebiopsis gigantea

We investigated the degree of genetic differentiation between geographically isolated populations of the saprophytic fungus Phlebiopsis gigantea from Europe and North America using two different molecular approaches: (i) denaturing gradient gel electrophoresis (DGGE) and sequence analyses of the ITS region, and (ii) genetic fingerprinting using random amplified microsatellite (RAMS) markers. The analysis included 84 homokaryotic single spore isolates of 28 European strains, 13 heterokaryotic strains from North America, and the Rotstop strain used as a biocontrol agent against Heterobasidion annosum.. Three different ITS-alleles (designated as ITS/A, ITS/B and ITS/C) were separable by the DGGE, two of them occurring both in Europe and North America. However, sequence determination of these allele types showed that while the ITS/B alleles were identical between Europe and North America, the ITS/C alleles contained differences. Analysis of molecular variation (AMOVA) and neighbor joining (NJ) clustering analysis using altogether 28 RAMS markers revealed a considerable degree of differentiation between the European and North American populations. The results show that recent human-mediated Il gigantea migration between the continents is unlikely and that strains should not be transferred between continents for biocontrol purposes in order to avoid the introduction of novel genotypes.