GEOGRAPHICAL CLINE OF DNA VARIATION WITHIN THE F INTERSTERILITY GROUPOF HETEROBASIDION-ANNOSUM IN ITALY

Eighty-six Heterobasidion annosum isolates, mainly belonging to the F intersterility group and obtained from 32 different geographical local ities in Italy, were subjected to genetic analysis by the Random Ampli fied Polymorphic DNA (RAPD) markers. The similarity between F and S gr oups was higher than that between F and P. In UPGMA Cluster Analysis, the F isolates originating from the same locality usually grouped in t he same cluster. The isolates also showed a tendency to group at the l evel of larger geographical areas. Within the F group, isolates from t he south of the Italian peninsula showed the highest genetic variation and northern isolates from the Alpine regions showed the lowest. This indicates a gradual dine along the peninsula. The genetic variability in the Italian F group is discussed in relation to the past and prese nt distribution of the host species in Italy and Europe.