Assessment of Compatibility among Armillaria cepistipes, A. sinapina, and North American Biological Species X and XI, Using Culture Morphology and Molecular Biology

Abstract

Ten single-spore isolates each of Armillar- ia sinapina, A. cepistipes, and North American bio- logical species (NABS)X and XI were paired in all combinations. A second set of ten single-spore iso- lates of each species was likewise paired. Each pairing was duplicated for a total of 3280 pairs. Using the standard morphological criteria (e.g., fluffy, crustose) to assess the pairings, A. sinapina exhibited the fol- lowing compatibility 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, respectively. NABS X was 70% selfcompatible and 4.0% compatible with NABS XI. NABS XI was 55% selfcompatible. The intergenic spacer region of the rDNA of each isolate was amplified using poly- merase chain reaction and digested with Alu I. Seven distinct restriction fragment length polymorphic (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. cep- istipes. By using the RFLP patterns as markers to as- sess the outcome of the pairings, it was determined that, in general, the morphological ratings were an accurate reflection of nuclear combination. Combin- ing the RFLP and pairing results confirms that NABS XI is compatible with A. cepistipes and should be con- sidered conspecific. A. sinapina, NABS X, and A. cep- istipes are compatible to a very limited degree in cul- ture, but not enough evidence exists to warrant re- ducing any to synonomy. Therefore, we believe NABS X should be formally described as a new species of