SPECIES DELIMITATION IN NORTH-AMERICAN SPECIES OF ARMILLARIA AS MEASURED BY DNA REASSOCIATION

The relatedness among biological species in Armillaria was explored us ing DNA reassociation experiments. Forty strains including nine of the ten reproductively isolated NABS (North American biological species) were used in the study. All of the biological species have significant levels of DNA sequence similarity with each other. Four major DNA seq uence similarity clusters were found. The first includes A. calvescens , A. gallica, A. sinapina, NABS IX and NABS X; the second includes A. mellea, with 17 isolates; the third includes A. gemina and A, ostoyae; and the fourth includes A. tabescens, which is the most distant with about 30% similarity with the other taxa. The results are discussed in regard to the relationships estimated by rRNA RFLP data.