Characteristics and Key Cultivation Techniques of the Han Xing No. 1 Strain

Han Xing No. 1 was introduced from South Korea by the author. Cultivation trials over several years have shown that this strain has a club-shaped stipe of fairly uniform thickness (see photo), and firm, crisp, tender fruiting bodies with an excellent taste. It is an outstanding variety among king oyster mushrooms. The main characteristics and key cultivation techniques of this strain are described below:

1 Biological characteristics

1.1 Nutrition Han Xing No. 1 requires relatively abundant nitrogen and carbon sources; the richer the nitrogen source, the better the mycelial growth and the higher the yield. It is generally believed that when the carbon-to-nitrogen ratio of the substrate is around 20:1, mycelial vigor increases and mushroom yield rises accordingly. Han Xing No. 1 has a strong ability to decompose cellulose and lignin, and can grow very well on substrates such as cottonseed hulls, waste cotton, soybean straw, broadleaf sawdust and corncobs. Practice has shown that the preferred substrate in production is cottonseed hulls, followed by willow and poplar sawdust of medium hardness. Adding cottonseed hulls and cornmeal to a conventional sawdust medium can promote mycelial growth rate, produce more mushroom primordia, and give high yields and good quality. However, when this strain is grown with rice straw as the main ingredient, even with added cottonseed hulls it shows delayed fruiting and low yield, so it is not suitable.

1.2 Temperature Han Xing No. 1 belongs to the type that fruits at moderate to slightly low temperatures. The mycelial growth temperature is 5-35°C, the suitable temperature is 22-27°C, and the optimum temperature is 25°C. Above 30°C the mycelium develops poorly, and below 20°C the mycelium grows slowly. The suitable temperature for primordium formation is 10-15°C, and the suitable temperature for fruiting body development is 15-21°C. Of particular note, below 10°C it is difficult for primordia to form, and above 22°C the quality of the fruiting bodies declines markedly, with deformed mushrooms appearing, and even rotten and dead mushrooms.

1.3 Moisture During the mycelial growth stage, the suitable moisture content of the substrate is 60%-65%. During fruiting body growth, water should not be sprayed onto the mushrooms. When mixing and bagging the substrate, the moisture content can be raised to 65%-70%, which is more suitable for the formation and development of fruiting bodies. During the fruiting body differentiation stage, the relative air humidity should be 85%-95%, which favors primordium formation and development; during the fruiting body growth stage, the air humidity can be appropriately lowered to 80%-90%.

1.4 Air Both mycelial growth and fruiting body growth require fresh air, but the mycelial growth stage requires relatively less oxygen, and low concentrations of carbon dioxide stimulate mycelial growth. In actual production, as the mycelium grows, when the carbon dioxide concentration in the substrate rises from the normal 0.03% to 2.2%, the mycelium grows vigorously and quickly. Primordium formation and growth, however, require sufficient oxygen; otherwise mushroom primordia form slowly and there are many deformed mushrooms, affecting yield and quality.

1.5 Light A dark environment favors mycelial growth, while fruiting body formation and development require a certain amount of scattered light, with a light intensity of 500-800 lx being suitable.

1.6 pH The optimum pH for the mycelial growth stage is 5-7, and for the fruiting body formation stage 5.5-6.5 is suitable.

2 Key cultivation techniques

2.1 Cultivation season Han Xing No. 1 has relatively strict temperature requirements; temperatures below 10°C or above 22°C are unfavorable for fruiting body growth. As with other strains, if the first flush fails to fruit normally, it will affect the normal occurrence of the next flush, or even result in no fruiting at all. Therefore, a suitable fruiting temperature is the key to successful cultivation. Generally, it is best to make the spawn 50 d in advance when the local temperature is below 20°C. In the Liaoning region, for autumn cultivation it is best to make the bags from mid-August to late September and to fruit after mid-October; for spring cultivation it is best to make the bags from mid-February to mid-March and to fruit in mid-April. With protected cultivation, this can be appropriately delayed or advanced.

2.2 Cultivation substrate Practice has shown that the best substrate for this strain is a mixture of sawdust and cottonseed hulls. The following formulas are provided for reference. ① Cottonseed hulls 35 kg, sawdust 15 kg; ② cottonseed hulls 25 kg, corncobs 17.5 kg, sawdust 7.5 kg; ③ cottonseed hulls 25 kg, corncobs 15 kg, sawdust 10 kg; ④ sawdust 35 kg, cottonseed hulls 15 kg; ⑤ sawdust 25 kg, cottonseed hulls 25 kg.

The above formulas all include the following supplements: wheat bran 7.5 kg, cornmeal 2.5 kg, soybean cake powder 1 kg, gypsum 0.5 kg, white lime 0.5 kg, with a moisture content of 60%-65%.

The main ingredient sawdust should be sieved. According to the capacity of the sterilization pot and the labor situation, pre-wet the main ingredient on the night before bagging; on the 2nd d add the supplements and mix evenly to a moisture content of 68%, then bag. Practice has shown that, if conditions permit, the main ingredient can be pre-wetted and fermented 3-5 d in advance, then the supplements added and the bags filled; this not only improves water-holding capacity but also induces the germination of contaminant fungal spores, making sterilization more thorough. Bagging, sterilization and inoculation are carried out according to the conventional methods used for making shiitake spawn.

2.3 Cultivation method The Han Xing No. 1 strain is mainly cultivated on sterilized substrate. For bag cultivation, 17 cm-33 cm × 0.04 cm plastic bags are generally used (holding 0.4-0.5 kg of dry substrate), fruiting from a single end. For large-scale cultivation, 15 cm × 55 cm × 0.04 cm plastic bags are used (holding 0.8-1.0 kg of dry substrate), with inoculation through holes on one side, giving better fruiting results, and being both convenient to manage and relatively lower in cost.

2.4 Fruiting management

2.4.1 Arranging the bags for fruiting Once the mycelium has fully colonized the bags, they can be arranged for fruiting. At present, bag-cultivation fruiting methods include upright bag arrangement, wall-type single stack fruiting from both ends, wall-type double stack fruiting from one end, and long-bag slanting upright fruiting, among others. Among these, upright fruiting is simpler to manage and gives good quality commercial mushrooms, but occupies a large area, while wall-type stacked bag cultivation puts a large amount of substrate per unit area and has high utilization efficiency; this method is mostly used in the Liaoning region. Before arranging the bags, first dig out the aged spawn at the inoculation holes to stimulate primordium differentiation, but care must be taken to avoid water accumulating in the inoculation holes.

2.4.2 Thinning primordia at the right time To ensure fruiting body quality, primordia that have differentiated too densely at the fruiting openings should be thinned at the right time, with 2-3 primordia retained per fruiting opening.

2.4.3 Regulation of environmental factors The primordium differentiation of the Han Xing No. 1 strain is relatively sensitive to temperature and tends toward constant-temperature fruiting. Too large a temperature difference is unfavorable for the occurrence of mushroom primordia. During fruiting, a relatively low ambient temperature and a relatively high relative humidity should be maintained. In practice, once the bags are fully colonized by mycelium, loosen the bag mouths (without opening them) while arranging the bags, to increase oxygen supply inside the bags; provide 300-500 lx of scattered light, ventilate 1-2 times a day, keep the air fresh, control the temperature at 18-22°C and the humidity at 75%-80%, and continue culturing for 7-10 d to let the mycelium fully mature; then lower the temperature to 12-15°C, raise the air humidity to 85%-95%, ventilate 2-3 times a day, and induce primordium formation. Throughout the management process, regulate the relationship among temperature, light, water and air as well as possible, and by no means allow hot, dry or strong wind to blow directly onto the fruiting bodies, which would cause the young mushrooms to turn yellow and shrivel.

The following points should be noted in fruiting management: ① The bag mouths must not be opened before primordia appear, so as to avoid the influence of unstable temperature, humidity and air in the external environment, which would block primordium formation or result in uneven fruiting. ② In the microclimate for fruiting, when the air temperature reaches above 20°C, mushroom primordia are not easily produced; above 22°C it will cause shriveling and even death; below 8°C no primordia appear; at 13-15°C fruiting is fast, with many primordia and uniform growth. After fruiting begins, control the temperature at 13-18°C; lowering the temperature to around 15°C in the later stage of mushroom development can markedly improve yield and quality. ③ During the primordium induction period, control humidity at 90%-95%; in the later stage of young mushroom development, control humidity at 80%-90%, to prevent long-term high humidity from causing disease. Keeping it slightly drier in the later management stage can extend the shelf life of the commercial product. When the air humidity is below 80%, spray water appropriately to increase humidity, but by no means spray water directly onto the fruiting bodies, as this would cause yellowing of the fruiting bodies and, in severe cases, rot. ④ Maintain good ventilation conditions; with good air, there will be more mushroom primordia, normal caps, good mushroom shape, good quality and high yield.