How to Induce Mushroom Fruiting in Oyster Mushrooms? Methods and Techniques Explained

Oyster mushroom (scientific name: Pleurotus ostreatus; also known as the oyster cap, rough-skinned oyster mushroom, oyster mushroom, black peony mushroom, and called Xiuzhen mushroom in Taiwan, China) is a species in the family Pleurotaceae, order Agaricales, under the Basidiomycota, and is a fairly common gray edible mushroom. Traditional Chinese medicine considers the oyster mushroom warm in nature and sweet in taste. It has the effects of dispelling wind and cold and relaxing the sinews and invigorating the collaterals. The oyster mushroom contains abundant nutrients; every 100 grams of the dried product contains 20—23 grams of protein, and its amino acid composition is complete in variety, with a very rich mineral content.

Morphological characteristics of the oyster mushroom

The oyster mushroom is an edible mushroom of the tetrapolar heterothallic type. The life cycle of the oyster mushroom is similar to that of many higher basidiomycetes, in which the mature fruiting body produces basidiospores. The basidiospores are ejected from the gills of the mature fruiting body, and upon encountering a suitable environment they grow germ tubes, which are initially multinucleate but quickly form septa, with each cell having one nucleus. [2] The germ tubes of the oyster mushroom continuously branch and elongate, forming monokaryotic hyphae. After monokaryotic hyphae of different sexes combine (plasmogamy),   the oyster mushroom forms dikaryotic hyphae. The dikaryotic hyphae have clamp connections on the septa. By means of the clamp connections, the dikaryotic hyphae continuously undergo cell division, produce branches, and under suitable environmental conditions grow and reproduce indefinitely. After a period of growth and development, the dikaryotic hyphae reach physiological maturity, and upon encountering suitable conditions of temperature, humidity, light, ventilation, and so on, they form clusters of granular primordia resembling mulberries, known as the "mulberry stage". After a few days they grow into short, uneven stipes shaped like mushroom caps, known as the “coral stage”, after which the stipes continuously elongate and thicken, and form caps at their tips, growing into fruiting bodies. In the hymenium, the tips of the dikaryotic hyphae produce basidia, whose genetic material undergoes recombination and segregation to form four basidiospores. After the spores mature, they are ejected from the gills, completing one life cycle.

How to induce fruiting in oyster mushrooms?

In oyster mushroom cultivation, some mushroom bags fail to fruit after the mycelium has fully colonized them, or after the first flush is picked, the second-flush primordia are slow to appear. In both of these cases, as long as the mushroom bags are colonized normally and the spawn temperature type is suitable, the following measures can be taken to achieve smooth fruiting. 1. Temperature difference stimulation: raise the temperature of the mushroom shed during the day and ventilate to lower the temperature at night; artificially widening the temperature difference can stimulate fruiting. 2. Light stimulation: after the mushroom bags are fully colonized, roll up the straw curtains of the mushroom shed every day and let sunlight shine for a period (do not expose them to direct sunlight when the light intensity is high). In trenches or mushroom houses where sunlight is inconvenient, electric light can be used for illumination. 3. Mycelium scratching stimulation: for cases where excessive addition of wheat bran, rice bran, urea, or other substances with high nitrogen content to the substrate causes an imbalance of carbon and nitrogen, mycelial overgrowth, and the formation of a mycelial skin that delays fruiting, or where fruiting is impossible because the bags were opened too early and the surface of the mushroom bags is too dry, a small claw-shaped rake made of iron wire can be used to gently scratch open the mycelial covering or mycelial skin; combined with ventilation, spraying a 0.5% glucose solution, and supplementary temperature difference and light stimulation, this can promote pinhead formation. 4. Primordium-startling stimulation: use a sterilized wooden board, tree branch, or the palm of the hand to gently pat the surface of the mushroom bed or the mushroom bags, so that the mycelium receives a vibration stimulus, promoting the formation of primordia. 5. Air stimulation: close doors and windows or cover with film to increase the carbon dioxide concentration, then ventilate twice a day for half an hour each time. 6. Casing soil and pressure stimulation: place tiles, wooden boards, or bricks on the mushroom bed or mushroom bags. For mushroom bed cultivation, covering with 1-1.5 cm of soil particles both prevents contaminating fungi and gives a better effect of retaining moisture and inducing fruiting. 7. Hormone and chemical stimulation: spray the surface of the mushroom bags or the mushroom bed with naphthaleneacetic acid at a concentration of 5 parts per million to 10 parts per million, or triacontanol at 0.1 parts per million to 0.5 parts per million. This method can not only advance fruiting but also increase yield.