Genetic diversity of Armillaria gallica isolates from China and Europe revealed with ISSR analysis

Armillaria gallica is a cosmopolitan fungal species found in the northern hemisphere, and genetic diversity and similarity between different continental isolates of the species can reveal important large-scale biogeographical patterns. A total of 79 isolates of A. gallica were collected from Europe and China. We esti- mated the genetic diversity of these isolates using ISSR (inter-simple sequence repeat) markers. Six ISSR primers were employed to identify a total of 210 scorable fragments, of which 202 (96.2%) were polymor- phic loci (frequecy<0.95). The average number of polymorphic loci detected with each primer was 33.6. The results indicated that ISSR markers can reflect abundant polymorphism in Armillaria. According to UPGMA clustering analysis, 49 out of 53 Chinese A. gallica isolates clustered into a China Group at the 0.773 similar- ity level. The genetic divergence of European isolates was significantly higher than predicted; these isolates were clustered into Europe Group A and Group B at the 0.775 and 0.763 similarity level, respectively. The