Selection and breeding of shiitake strains resistant to Trichoderma spp.

Bedlogs of shiitake, Lentinula edodes (Berk.) Pegler, are often attacked by Trichoderma spp. such as T. harzianum Rifai and T. polysporum Rifai, which produce antifungal substances and mycolytic enzymes. However, shiitake is more or less able to reject Trichoderma attacks. Shiitake cultures possess at least five straight-chain alcohols with double and triple bonds, which act as antifungal substances. Trichoderma inoculation tests for shiitake cultures showed that the resistance of shiitake in a wood-powder medium correlated positively with that in bedlogs when T. harzianum was used. Screening assays using the wood-powder medium showed some highly resistant and susceptible strains among 164 different wild shiitake strains. Monokaryons derived from basidiospores of a highly resistant strain, TMI-407, had high rejecting abilities compared with those from a susceptible strain, TMI-1161. Crossing between monokaryons from the two strains revealed that resistance was dominant. In general, these resistant mycelia produced much more antifungal substances than did susceptible mycelia. Key words: Lentinula edodes, shiitake, mushroom cultivation, resistance to Trichoderma spp., selection method, antagonism.