An Investigation of Spawn Growth of Pleurotus ostreatus in Heat-Tolerant Plastic Bags Using Rice and Corn as Substrates

Indonesian mushroom farmers commonly produce Pleurotus ostreatus spawn in bottles. Bottles have several disadvantages: unsterilized lids, large weights, undetectable bacterial contaminations, and difficulties in removing the rest of mycelia around the edge of the bottle. Farmers rarely use plastic bags due to unfamiliarity. Therefore, in this study, we investigate growth of P. ostreatus spawn in heat-tolerant plastic bags using three different substrates (corn, rice, and a mixture of corn and rice). The physiological and morphological properties of mycelia growth on substrates were assessed, including growth rate, type of mycelium, and colony formation. Grain moisture is an important factor to get a successful spawn. We estimated the suitable water content of corn and rice in plastic bags was 50% and 27%, respectively. Inoculation of inoculum from potato dextrose agar (PDA) into grains was called first-generation spawn (G1). The corn medium showed the fastest growth (2 weeks), followed by the mixture of corn and rice (4 weeks), followed by the rice medium (6 weeks). Inoculation of G1 into another grain was called second-generation spawn (G2). Inoculation of G1 into G2 from corn to corn mycelia grew for 1 week, from the mixture of corn and rice on the same substrate for 2 weeks, and the slowest growth was in mycelium from rice to rice substrate for 4 weeks. An application of spawn to mushroom cultivation showed that farmers are able to expand G2 into 30-50 of sawdust fruiting body substrate. From the three types of spawn, farmers reported that they obtained good mushroom yield when the mixture of corn and rice was used as spawn. This study may be useful for new methods to generate spawn.