Sibling spore isolates of Tricholoma matsutake vary significantly in their ectomycorrhizal colonization abilities on pine hosts in vitro and form multiple intimate associations in single ectomycorrhizal roots

Tricholoma matsutake is a commercially important edible ectomycorrhizal mushroom. The ecology of this species has emerged from studies of the genetic background of mycelial colonies in nature. Single putative colonies sometimes comprise several genets. This complex mycelial structure should be subjected to analysis to determine its ecophysiological significance. We tested the ectomycorrhization ability of nine T. matsutake sibling spore isolates. The ectomycorrhizal colonization ratio differed significantly among isolates, and was dependent on the soil nitrogen content. Mixed inoculations of three selected isolates into soils in which single pine seedlings were grown showed that the isolates interacted in the seedling roots. Paired inoculations of isolates #52/#99 and #52/#84, and a triple inoculation of isolates #52/#84/#99 resulted in levels of ectomycorrhizal colonization that significantly exceeded the colonization levels following single isolate inoculation. We suggest that mycelial interaction between sibling isolates is a significant phenomenon that operates within individual ectomycorrhizal pine root tips.