IDENTIFICATION OF THE GENUS ARMILLARIA BY SPECIFIC AMPLIFICATION OF AN RDNA-ITS FRAGMENT AND EVALUATION OF GENETIC-VARIATION WITHIN A-OSTOYAE BY RDNA-RFLP AND RAPD ANALYSIS

Genetic variation among Armillaria ostoyae isolates was studied by rDN A-restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis. A total of 20 A. ostoyae isolates, m ainly obtained from Picea spp. of different geographical origins, were examined. Southern hybridization of whole-cell DNAs digested with Ava II and probed with biotin-labelled cloned rDNA from Saccharomyces carl sbergensis allowed :he differentiation of five RFLP groups. UPGMA clus ter analysis of RAPD profiles (138 scorable bands) generated by 10 dec amer primers (OPA 01-OPA 10) grouped the isolates in subclusters at si milarity levels between 40% and 96%, indicating high intraspecific gen etic variability. Some isolates of different geographical origins subg rouped together, suggesting that similar mutational events have occurr ed independently and that genetic exchange and recombination occurs am ong the DNAs in natural populations. The potential role of historical and current spread of spruce plants on the genetic variation of A. ost oyae isolates in Europe is discussed. Using the primer pair ARM-1 and ARM-2, an Armillaria-specific ITS-DNA fragment of about 660 bp was obt ained. No intraspecific RFLP of this amplicon could be revealed, indic ating low genetic variability of this region. The established informat ive RFLP and RAPD markers and also the Armillaria-specific ITS-DNA fra gment may be powerful tools for further epidemiological, phylogenetic and host-pathogen interaction studies with A. ostoyae.