Abstract
Sporocarps of the ectomycorrhizal fungus Laccaria laccata var. moelleri were collected in association with black spruce on peatlands in northern Minnesota and central Canada. Pairings between homokaryotic mating-type reference cultures obtained from the sporocarps indicated an absence of any heterogenic incompatibility barriers. The number of homogenic incompatibility alleles in the species was estimated to be 17 at the A locus and 18 at the B locus. These estimates are much lower than those reported for other basidiomycetes. Outbreeding efficiency was estimated to be 88.6%.