RESUMO
Aim: Developing high yielding single spore isolates and hybrid strains of paddy straw mushroom (Volvariella volvacea) with superior nutritional composition of the fruiting bodies.Methodology: Two contrasting high yielding strains (DMRO-463 and DMRO-484) of V. volvacea previously released for higher fruiting body yield were used for isolation of single spore isolates (SSIs). The slow growing SSIs were used for developing the hybrid strains by mating on Malt Extract Agar Medium Petri dishes. Conversely, the fast growing SSIs and the developed hybrid strains were screened for downward mycelial growth on paddy straw filled in wide mouth test tubes. Based upon downward mycelial growth, only eight SSIs and ten hybrid strains with numerically higher downward mycelial growth compared to two parents' checks were further evaluated for fruiting body yield on composted cotton ginning mill waste substrate under indoor conditions. Results: In successive yield evaluation trials (one preliminary and three full scale), hybrid strains VvH-11, VvH-13 and VvH-18 gave fruiting body yield higher than the two parents. Out of these hybrids, the yield distribution at different height (selves) in growing room was consistent in hybrid VvH-13 in trial-2, while rest two hybrids and parents showed significantly lower yield in lowest self (30 cm above floor level). The fruiting body weight also showed similar trend. The fruiting bodies from the highest yielding hybrid VvH-11 exhibited highest level of crude fiber (2.07%) and ash (10.95%) contents, while the hybrid VvH-13 giving consistent yield across growing room exhibited higher level of crude fiber (2.00 %), vitamin C (52.35 mg 100 g-1) and vitamin D (1434.7 µg 100 g-1). The third hybrid VvH-18 was superior in crude fiber (1.74%), manganese (22.46 ppm), selenium (0.26 ppm) and vitamin C (43.13 mg 100 g-1). All three hybrids exhibited lower fat (1.54 to 1.86 %) content compared to parents (2.54 to 2.59 %). Interpretation: High yielding hybrid strains can be developed in paddy straw mushroom (V. volvacea) through mating of slow growing SSIs, and their screening involving downward mycelial growth on paddy straw and repetitive grow out trials.