Root-associated bacteria influencing mycelial growth of Tricholoma matsutake (pine mushroom)

Tricholoma matsutake is an ectomycorrhizal fungus usually associated with Pinus densiflora in South Korea. Fruiting bodies (mushrooms) of T. matsutake are economically important due to their attractive aroma; yet, T. matsutake is uncultivatable and its habitat is rapidly being eradicated due to global climate change. Root-associated bacteria can influence the growth of ectomycorrhizal fungi that co-exist in the host rhizosphere and distinctive bacterial communities are associated with T. matsutake. In this study, we investigated how these bacterial communities affect T. matsutake growth by isolating bacteria from the roots of P. densiflora colonized by ectomycorrhizae of T. matsutake and co-culturing rootassociated bacteria with T. matsutake isolates. Thirteen species of bacteria (27 isolates) were found in pine roots, all belonging to the orders Bacillales or Burkholderiales. Two species in the genus Paenibacillus promoted the growth of T. matsutake in glucose poor conditions, likely using soluble metabolites. In contrast, other bacteria suppressed the growth of T. matsutake using both soluble and volatile metabolites. Antifungal activity was more frequent in glucose poor conditions. In general, pine rhizospheres harbored many bacteria that had a negative impact on T. matsutake growth and the few Paenibacillus species that promoted T. matsutake growth. Paenibacillus species, therefore, may represent a promising resource toward successful cultivation of T. matsutake.