Distribution and diversity of vegetative compatibility types in subpopulations of Cryphonectria parasitica in Italy

Using a medium that discriminated with high resolution, 20 vegetative compatibility (vc) types were detected among a sample of 716 isolates of Cryphonectria parasitica from 11 widely separated subpopulations throughout Italy. Each isolate was assigned unambiguously to a single vc type; no isolates were compatible with more than one vc type. Most isolates (85%) were in four common vc types; the other 16 vc types were represented by only a few isolates each. Vegetative compatibility type frequencies were markedly different between northern and southern Italy. Three of the most common vc types (I-1, I-2 and I-5) were found mostly in the North, where diversity was greatest, while two others (I-10 and I-12) were primarily found in the South.