SINOPSIS

An artificial fertile hybrid was created by protoplast fusion between a cultivar Ganoderma tsugae Murrill and a field isolate of G. lucidum (W. Curt.: Fr.) Lloyd for expanding the growth temperatures favoring production throughout the year. Actively growing mycelia were digested using 2% lywallzyme in 0.6 M mannitol to yield 228 × 10³ and 178 × 10³ protoplasts g⁻¹ for G. lucidum and G. tsugae, respectively. Fusion of protoplasts was chemically induced by 30% polyethylene glycol, and the protoplast regeneration efficiency was 4.0 ± 0.2%. Positive screening was carried out by determining the survival and growth rates of the putative hybrids from 18 °C to 40 °C. After several fruiting tests, a stable hybrid was selected. Characterized by unique DNA fingerprints, it consistently produced basidiomes and basidiospores in 1.5 months using a formulated sawdust/coconut fiber substrate. Also, this artificial hybrid gained an antiproliferative property on colon cancer cells from the G. lucidum parent in an in vitro study. Oral consumption of the hybrid extract caused rapid hypoglycemic effect on BALB/c mice even after the challenge of carcinogenic streptozotocin. Also, it enhanced the recovery of cytokine expression in streptozotocin-treated mice, although there was not a horizontal transfer of an immunoprotein LZ-8-encoding gene from the parental cultivar. Thus, this study first reports the in vivo immunorecovery effect of lingzhi, demonstrates the use of protoplast fusion to cross the natural incompatibility of two biological species in the medicinal Ganoderma lucidum species complex, and demonstrates hybrid vigor for sustainable lingzhi production and commercialization.