ASSESSMENT OF COMPATIBILITY AMONG ARMILLARIA-CEPISTIPES, ARMILLARIA-SINAPINA, AND NORTH-AMERICAN BIOLOGICAL SPECIES-X AND SPECIES-XI, USINGCULTURE MORPHOLOGY AND MOLECULAR-BIOLOGY

Ten single-spore isolates each of Armillaria sinapina, A. cepistipes, and North American biological species (NABS)X and XI were paired in al l combinations. A second set of ten single-spore isolates of each spec ies was likewise paired. Each pairing was duplicated for a total of 32 80 pairs. Using the standard morphological criteria (e.g., fluffy, cru stose) to assess the pairings, A. sinapina exhibited the following com patibility levels: 68% with itself, 5.5% with A. cepistipes, 3.5% with NABS X, and 5% with NABS XI, respectively. Armillaria cepistipes was rated 53%, 6.5%, and 57% compatible with itself and NABS X and XI, res pectively. NABS X was 70% selfcompatible and 4.0% compatible with NABS XI. NABS XI was 55% selfcompatible. The intergenic spacer region of t he rDNA of each isolate was amplified using polymerase chain reaction and digested with Alu I. Seven distinct restriction fragment length po lymorphic (RFLP) patterns were observed: two in A. cepistipes, two in A. sinapina, one in NABS X, one in NABS XI, and one that was common to NABS XI, and A. cepistipes. By using the RFLP patterns as markers to assess the outcome of the pairings, it was determined that, in general , the morphological ratings were an accurate reflection of nuclear com bination. Combining the RFLP and pairing results confirms that NABS XI is compatible with A. cepistipes and should be considered conspecific . A. sinapina, NABS X, and A. cep istipes are compatible to a very lim ited degree in culture, but not enough evidence exists to warrant redu cing any to synonomy. Therefore, we believe NABS X should be formally described as a new species of Armillaria.