Ectomycorrhiza formation ofTricholoma matsutake onPinus densiflora

Mycorrhizal association ofTricholoma matsutake withPinus densiflora was studied. A naturally establishedP. densiflora stand (age: ca. 45 yr) where occurrences ofT. matsutake sporocarps had been confirmed was studied in lbaraki Prefecture, Japan. Pine root systems connected withT. matsutake sporocarps via the fungal white mycelia were sampled in October 1997. The sampled pine roots were covered overall with mycelia. Under a dissecting microscope, the mycelia were confirmed to form fungal sheaths on the lateral roots. Under a light microscope, transverse and longitudinal sections of these roots showed the presence of both fungal sheaths and Hartig nets, which are typical of ectomycorrhizas. The fungal sheath was ca. 1.5–20 μm. in thickness, and felt prosenchymatous in texture. Hartig nets developed continuously at the cortex and extended to the boundary between cortical cells and endodermal cells. The same ectomycorrhizal morphotype on the pine was also recovered from inside the same mycelial colony (i.e., “shiro”) ofT. matsutake from winter to summer. These results suggest thatT. matsutake has a perennial ectomycorrhizal association withP. densiflora.