ABSTRACT
Rhizopogon roseolus (Corda) Th. M. Fr. (=R. rubescens Tul. & Tul.), known as “shoro” in Japanese, is a hypogeous basidiomycete that is an important ectomycorrhizal symbiont of the Pinaceae. In order to cultivate this edible ectomycorrhizal mushroom, several researchers have tried to promote ectomycorrhization of this mushroom on roots of its host, Pinus thunbergii: Pine seedlings were inoculated with mycelium in vitro, or with crushed fruiting bodies in nature. However, this mushroom has not been successfully cultivated. We have developed useful mycelial slurries that enable production of abundant ectomycorrhizas and promote fruiting body formation under greenhouse nursery. We selected a superior isolate that rapidly colonized and produced a lot of ectomycorrhizas in roots of P. thunbergii. The mycelial slurries were composed of saline solution and a homogenate of a submerged culture of the mycelium. Addition of surfactant to the mycelial slurries resulted in stimulation of ectomycorrhizal formation in host roots. When the mycelial slurries were injected into a mother plant system in which the colonized seedling had been planted in the nursery, stimulatory effects were observed not only on ectomycorrhization of the seedlings but also on fruiting body formation. Genotype analysis of the fruiting bodies produced in the nursery showed that they had been produced by the inoculated isolate. These results suggest that the mycelial slurries could serve as mycelial spawn for cultivation of shoro.