Genetic analyses of causal genes of albinism (white fruiting body) in Grifola frondosa

The tyrosinase 2 gene ( tyr2 ) from two compatible strains of Grifola frondosa , the albino-type monokaryon strain IM-WM1-25 and the wild-type monokaryon strain IM-BM11-P21, were amplified and characterized (designated tyr2 −Δ25 and tyr2 + , respectively). A single base deletion in the coding region of tyr2 −Δ25 from IM-WM1-25 was discovered, and this mutation is predicted to cause a frame-shift in translation, yielding inactive protein tyrosinase protein 2 (TYR2). Polymerase chain reaction (PCR) primer pairs were designed to detect normal tyr2 + and mutant tyr2 −Δ25 , and then the tyr2 genotype of F1 progenies, which was obtained from basidiospore isolation of IM-BM11-P21 × IM-WM1-25 ( tyr + × tyr2 −Δ25 ) strain, was analyzed. Back-crossing (F1 progenies × IM-WM1-25) was performed and fruiting body colors of the crossed strains were analyzed. The fruiting bodies of all crossed strains were white and beige, and the corresponding genotypes were tyr2 −Δ25 × tyr2 −Δ25 and tyr + × tyr2 −Δ25 . These results suggest that the causal gene of the albino mutation is tyr2 and this study provides a new strategy for the breeding of albino mushrooms belonging to G. frondosa .