Growth stimulation of a Shiro-like, mycorrhiza forming, mycelium of Tricholoma matsutake on solid substrates by non-ionic surfactants or vegetable oil

The incorporation of Tweens (1 %, 2 %, 5 %) or olive oil (1 %, 2 %) in soil or in soil-containing substrate strongly stimulated mycelial growth of the edible ectomycorrhizal mushroom Tricholoma matsutake (Matsutake) after 1 or 3 months, respectively. The growth responses to Tween 40 and Tween 80 were dose-dependent. Fungal biomass increased up to 15-fold as a result of olive oil incorporation. After 4 months of Matsutake/pine co-culture in the presence of olive oil (2 %), compact aggregates of substrate, hyphae, and surface-colonized roots were observed, recalling in some ways the mycelial mat structure of Matsutake in the field, i.e. Shiro. Olive oil did not prevent formation of well-developed Hartig net palmettis although those seemed rather less abundant than without oil addition. The incorporation of Tween 80 or olive oil (2 %) into nutrient agar induced the proliferation of peripheral hydrophilic-like hyphae penetrating the medium. Tricholoma matsutake growth stimulation, possibly related to the presence of fatty acids in surfactants and oil, could be a consequence of the higher hydrophilicity of treated hyphae, or of enhanced lytic enzyme excretion and activity. Parameters such as adjuvant type, concentration, and growth conditions will be further optimised to formulate culture substrates adapted to the co-culture of T. matsutake and its host plants.