A New Record of Auricularia heimuer in Thailand: Optimal Conditions for Mycelial Growth, Inoculum Production, Cultivation Performance and a Favorable Nutritional Profile

Auricularia heimuer, an economically important edible mushroom species, is reported for the first time in Thailand based on combined morphological and molecular analyses. Three strains (SL115, SL150, and SL160) were collected from decaying wood in dipterocarp forests in Phayao and Lampang provinces, northern Thailand. Phylogenetic analyses based on combined ITS and nLSU sequence data confirmed their identity as A. heimuer, with morphological characteristics consistent with the type description. Mycelial growth experiments demonstrated that culture medium, temperature, pH, and nitrogen source significantly influenced mycelial growth and biomass production. Potato dextrose agar (PDA) was the most suitable medium for strains SL115 and SL150, whereas corn dust agar (CDA) was optimal for SL160. All strains exhibited optimal growth at 30 °C under acidic to neutral pH conditions and in media supplemented with organic nitrogen sources, particularly tryptone, peptone, and yeast extract. For inoculum production, potato dextrose broth and corn stalk-based media were the most suitable substrates for liquid spawn, while corn kernels and barley were optimal for grain spawn, rubber sawdust for solid spawn, and lotus stalk, giant mimosa stalk, and rubber tree wood for stick spawn. Cultivation trials showed that A. heimuer strains SL115 and SL150 produced lower yield and biological efficiency (BE) than A. cornea SL167 when grown on a 100% rubber sawdust substrate. However, supplementation of the cultivation substrate with Dipterocarpus or teak leaves significantly improved productivity. Among the tested treatments, T10 (A. heimuer SL150 cultivated on a substrate containing 50% rubber sawdust and 50% Dipterocarpus leaves) achieved the highest yield (43.86 g per bag) and BE (37.59%). The fruiting bodies showed favorable nutritional properties, including high carbohydrate, moderate protein, and low-fat contents. These findings establish A. heimuer as a newly recorded, cultivable mushroom species in Thailand and provide fundamental data on its optimal cultivation parameters, suitable spawn substrates, and nutritional value to support its further development for local mushroom production.