Genetic diversity in populations of Cronartium ribicola in plantations and natural stands of Pinus strobus

Abstract
Genetic diversity was studied in 22 populations of the white pine blister rust fungus Cronartium ribicola from natural stands and plantations of eastern white pine, Pinus strobus. Pseudo-allelic frequencies were estimated at each of 7 putative RAPD loci by scoring for presence or absence of amplified fragments in dikaryotic aecidiospores. Analysis of genetic distance between all pairs of populations did not reveal any trend with regard to geographic origin or type of white pine stand. In addition, when hierarchical population structure was analysed, total genetic diversity (H s =0.214) was mostly attributable to diversity within populations (H s =0.199; AMOVA φ st =0.121, P0.10) Nevertheless, a significant proportion of genetic differentiation was found between populations within region or stand type (F st =0.114; φ sc =0.132, PC. ribicola may still be expanding its distribution by colonizing new plantations.