DELINEATION OF THE EUROPEAN ARMILLARIA SPECIES BASED ON THE SEQUENCESOF THE INTERNAL TRANSCRIBED SPACER (ITS) OF RIBOSOMAL DNA

Variation within the internal transcribed spacer (ITS) of the ribosoma l RNA gene of 15 isolates representing seven European Armillaria speci es, was examined by sequencing of the PCR-amplified products. The anal ysis of an 744-bp region showed that the 5.8S gene appeared to be high ly conserved in the 15 isolates and in other Basidiomycetes and Ascomy cetes, whereas ITS1 and especially ITS2 spacers exhibited polymorphism s due to base substitutions, insertions or deletions of up to eight nu cleotides. An initial dendrogram for the full sequence was drawn using cluster analysis (UPGMA), and a tree was constructed using the maximu m parsimony method. Both methods indicated that the isolates could be divided into four major groups. One group, consisting of A. ectypa, wa s distinct from all the other species. Examination of the other groups indicated that A. tabescens and A. mellea were in a separated cluster , with a significant variation between the two isolates of the latter species. A. gallica and A. cepistipes constituted another closely rela ted group distinguishable from A. ostoyae and A. borealis, these latte r two species exhibiting the highest similarity. The results are consi stent with, and discussed in regard to, the relationships estimated pr eviously by pairing tests, morphological and physiological comparisons , as well as by restriction fragment length polymorphism of the rDNA.