PHYSIOLOGICAL DYNAMICS OF SPORE GERMINATION AND INTERSPECIFIC MATING COMPATIBILITY IN OYSTER MUSHROOMS (PLEUROTUS SPP.)

Abstract

Commercial cultivation of oyster mushrooms (Pleurotus spp.) is frequently constrained by narrow thermal adaptability and yield plateaus. In this study, seven commercial Pleurotus species were evaluated for agronomic traits, sporophore morphology, and basidiospore physiology to facilitate targeted interspecific hybridization. Cumulative yield ranged from 469.3 g in P. ostreatus (52.14% biological efficiency [BE]) to 645.5 g in P. djamor (71.72% BE). Although P. ostreatus yielded the lowest total biomass, it produced the heaviest individual basidiomes (13.40 g), whereas P. djamor exhibited the highest flush count (74 basidiomes). Four candidate taxa—P. sajor-caju, P. djamor, P. flabellatus, and P. ostreatus—were selected for downstream breeding. Basidiospore germination peaked uniformly at 27°C (62.1%–68.3%) and neutral pH 7.0 (61.0%–68.8%) after 48 h, with severe inhibition at 15°C and pH extremes (4.0 and 10.0). Exogenous sugars exerted osmotic repression compared to sterile water (62.1%–70.1%). Low-temperature preservation (6°C) maintained high spore viability (54.2%–57.0%) up to 150 d versus rapid loss at 27°C (21.0%–22.2%). Single-spore isolates confirmed tetrapolar heterothallism across all four species, displaying slow-growing hyphae devoid of clamp connections and complete basidiome sterility. Interspecific confrontation of 19 verified monokaryons across 135 pairings yielded 27 fertile dikaryotic hybrids (20.0% compatibility) verified by clamp connections. The cross P. djamor $\times$ P. flabellatus exhibited the highest crossability (36.0%), while P. djamor $\times$ P. ostreatus demonstrated strong pre-zygotic barriers (8.0%). Selected hybrids manifested prominent heterosis, combining the fleshy basidiome architecture of temperate taxa with the vibrant pigmentation and fecundity of tropical lines.