Effects of Different Nutrient Media on Mycelial Growth Quality During Pure Culture and Spawn Production Stages of White Oyster Mushroom (Pleurotus ostreatus var. Florida)

Potato Dextrose Agar (PDA) has been widely recognized in mycological research for its effectiveness in cultivating a broad spectrum of fungi, including edible mushrooms such as Pleurotus ostreatus. However, the high cost of commercial agar limits its accessibility for local mushroom growers. Therefore, this study aims to investigate the potential of low-cost agar formulations and other alternatives to PDA in a laboratory setting. Five treatments were applied: PDA (control), Malt Extract Agar (MEA), Murashige and Skoog (MS), Rice Water Agar (RWA), and Potato Sucrose Agar (PSA). The experiment was arranged in a complete block design with three replications. Data were collected at two stages of oyster mushroom cultivation: pure and spawn culture. The mycelial growth quality was determined. Results revealed that, at the pure culture stage, RWA had the highest mycelial growth rate at 9 days after inoculation (DAI) with 7.73 cm, but there was no statistical difference compared to PSA and PDA. MEA obtained the highest mycelial weight at 1.08 g. PSA, MEA, and RWA favored mycelial visual parameters, while PDA, PSA, and MEA favored thickness. RWA showed the highest growth vigor, and MEA and PDA the highest mycelial density. RWA completed the stage in 9.30 days, including the time mycelium appears at 1.03 days. No contamination occurred at RWA. At the spawn culture stage, RWA had the highest mycelial growth rate at 11.50 cm in 12 DAI. RWA was also high at mycelial visual parameters. MEA completed the stage in 14.87 days with comparable results in mycelial germination in all treatments except MS. Contamination occurred at the spawn stage, with high contamination observed in MS at 26.67%. Contamination during spawn and culture stages is influenced by inoculation technique and environmental conditions, not just the media. Temperature and RH significantly affected weight and color score. The MS medium showed the least favorable performance, likely due to its high salt content being unsuitable for fungal growth. This study provides a reference for mycelial growth quality on how mycelium behaves across two stages of oyster mushroom production.