THE RELATEDNESS OF THE ITALIAN-F INTERSTERILITY GROUP OF HETEROBASIDION-ANNOSUM WITH THE S-GROUP, AS REVEALED BY RAPD ASSAY

The PCR technique based upon randomly amplified polymorphic DNA (RAPD) markers using 10-mer oligonucleotide primers was used to investigate the phylogenetic relationships among 33 isolates of Heterobasidion ann osum belonging to the intersterility groups F and S. The F isolates or iginated from Italy, the S isolates from the Italian Alps, northern Eu rope and North America. The presence or absence of some bands was show n to be population-specific. The North American S group and the Europe an S group differed significantly from each other, but within the latt er group there were no significant differences between the Italian S a nd the northern European S populations, with as much similarity within these populations as between them. More DNA polymorphisms appeared wi thin European F and S groups than in the North American S group. The N orth American S group appeared to be more closely related to the Europ ean S group than to the F group. The isolates of the Italian F populat ion seemed to be most closely related to the Italian S isolates and th en in decreasing order, to the northern European S and North American S isolates. The order of genetic similarity was inversely correlated w ith the mating frequency in vitro obtained in an earlier study.