Species delimitation in the Armillaria mellea complex by analysis of nuclear and mitochondrial DNAs

Nuclear and mitochondrial DNAs were isolated from mycelia of two different isolates of Armillaria mellea, A. bulbosa and A. obscura originating from widely separated localities. Nuclear GC contents ranged from 46.0 to 48.1 mol%. Nuclear DNA-DNA homologies obtained by a fast spectroscopic method were 90–100% for intraspecific hybridizations and 44–70% for interspecific hybridizations. Restriction enzyme cleavage patterns of mitochondrial DNAs using six different restriction enzymes yielded interspecific similarities from 0 to 50% and intraspecific similarities from 67 to 100%. Phylogenetic distances of the fungal species could not be deduced unequivocally from the mtDNA restriction data. Average mitochondrial genome sizes were estimated to be between approximately 90 and 100 kb.