Key Techniques of Cultivation of Stropharia rugosoannulata

Senlin ZHU, Qinyu ZHANG, Bo CHEN, Xiaomin WANG, Bangxi ZHANG

Institute of Soil and Fertilizer, Guizhou Academy of Agricultural Science, Guizhou 550006, China

Abstract Stropharia rugosoannulata is a straw rotting edible fungus that has developed rapidly in recent years. In the process of cultivation, key technologies have a huge impact on its yield. The key techniques for the cultivation conditions and modes of S. rugosoannulata were summerized to promote the realization of stable and high yield of S. rugosoannulata.

Key words Stropharia rugosoannulata, Cultivation conditions, Cultivation mode, Cultivation techniques

1 Introduction

Strophariarugosoannulatais one of the main edible fungi traded in the international edible mushroom market. The mushroom is delicious in taste, simple in cultivation technology and easy to obtain high yield, so it is very popular among the cultivators in China. Especially because the mushroom adapts to a wide range of environments and has strong stress resistance, the cultivation in the north and south of China develops rapidly. However, there are still some technical defects in the current cultivation process of the mushroom, which hinder the development of the mushroom industry. Therefore, only by solving these deficiencies can the economic benefit of the mushroom cultivation improve.

2 Cultivation conditions

Growth conditions ofS.rugosoannulataare as follows: the mycelium should be cultured for 25-45 d at the temperature of 21-27 ℃, the water content of 70%-75% in the culture material, the CO2concentration of less than 2%, and ventilation frequency of 0-1 time/h. The formation of mushroom buds and primordium differentiation takes 14-21 d, which is conducted under the conditions of temperature 10-16 ℃, relative humidity 95%-98%, CO2concentration less than 0.15%, ventilation frequency 4-8 times/h (or according to CO2concentration), light 100-500 lx. The development and growth of the fruit body requires 7-14 d, and the suitable condicitons are as follows: temperature 16-21 ℃, relative humidity 85%-95%, CO2concentration less than 0.15%, ventilation frequency 4-8 times/h, light 100-500 lx; the fruiting interval is 3-4 weeks.

Guizhou has advantages of good climate and ecological resources, where there are many microclimate environments. According to the growth habit ofS.rugosoannulata, local climate characteristics, the difficulty of obtaining culture materials and the market price, the planting time should be reasonably arranged. In low-altitude areas such as Huishui, Luodian, Xingyi, Guanling, Zhenning, Wangmo, and Ceheng, it can be planted around November, and will be on the market from New Year’s Day to the Spring Festival; it can also be planted again in spring. In medium-altitude areas such as Guiyang, Anshun and other areas in Guizhou, it should be planted around September and will be on the market from the National Day to New Year’s Day. In high-altitude areas such as Liupanshui, Weining and other places, it can be planted around June, and will be on the market in summer. In Guizhou Province, it can be planted in winter fallow fields in winter and spring[1].

3 Cultivation modes

3.1 Cultivation in winter fallow fieldsThe cultivation ofS.rugosoannulatain winter fallow fields is essentially "rice-mushroom" rotation, which is the main cultivation mode ofS.rugosoannulatain Guizhou. It mainly uses the empty space of paddy fields in winter for cultivation on the border, which does not conflict with the growth time of rice, can improve the utilization rate of land and increase the income of farmers. BeforeS.rugosoannulatais cultivated in winter fallow fields, the strains should be cultivated in advance to ensure that the sowing ofS.rugosoannulatais completed within 1 month after rice is harvested.

3.2 Under-forest cultivationFor under-forest cultivation ofS.rugosoannulata, orchards and bamboo forests with enough space are generally chosen, and the trees should be relatively sparse. For large-scale cultivation, fruit forests or timber forests with a row spacing of more than 2 m should be selected to facilitate machinery operations for land preparation and installation of spray equipment.

3.3 Greenhouse cultivationIdle greenhouses and vegetable stubble greenhouses are used to simply cultivateS.rugosoannulata.

4 Cultivation techniques

4.1 Strain preparation and material preparation

4.1.1Variety selection. At present, there are very few varieties ofS.rugosoannulata. The commercially available strains are mainly derived from the descendants of the strain ST0128 introduced by the Institute of Mycology in Sanming City, Fujian Province, the No.1S.rugosoannulatabred by the the Sichuan Academy of Agricultural Sciences, and No.1 HeinongS.rugosoannulatabred by the Heilongjiang Academy of Agricultural Sciences. ST0128 has wide adaptability and can be planted in areas with an altitude of 800-2 500 m. The fruiting body of No.1S.rugosoannulatahas red ochre pileus, white stipe, and dirty white gill; the fruiting body is large in piece weight, and the yield is high; the biotransformation rate is up to 45%, and it is difficult for the mushroom to open like umbrellas; the fruiting temperature is wide. For the No.1 HeinongS.rugosoannulata, the mycelium grows robustly, with strong resistance to impurities, thick stipe and pileus, good quality and high yield[1].

4.1.2Strain preparation. Preparation of mother strains: formula 1∶1 g of KH2PO4, MgSO4, yeast powder, and peptone are added to 1 000 mL of conventional PDA medium; formula 2: potato 20%, sucrose 2.5%, corn flour 0.4%, peptone 0.1%, 6-BA 0.5 mg/L, agar 2%, and water 1 000 mL. The culture temperature was 26 ℃.

Preparation of original strains and cultivated strains: formula 1∶75% of chaff, 25% of mixed sawdust, and 75% of water content; formula 2∶80% of chaff, 10% of mixed sawdust, 10% cottonseed husk, 75% of moisture content; formula 3∶75% of chaff, 25% of mixed sawdust, and 75% of moisture content.

The preparation of mother strains is 20-25 d earlier than that of original strains, and the preparation of original strains is 30-45 d earlier than that of cultivated strains[2,4].

4.1.3Preparation of culture material. Raw material cultivation method: corn stalks, rice stalks and other agricultural wastes are used as the culture material, and they are properly crushed to a length of about 5 cm; they are soaked in 2% quicklime water or water for 1-3 d before inoculation, and then drained for 12-24 h until the water content is up to 65%-70%. As the spray method is used, the culture material is turned over and mixed while spraying water, which is repeated 4-5 times every 3-4 h until the culture material is completely soaked. To judge water content, a handful of cultivating material is squeezed out discontinuous water droplets, and the water content is about 65%. If the water content is too high, water needs to be drained; if it is too low, water should be added.

Processed material cultivation method: (i) Selection and cleaning of fermentation farms. It is best to choose a hardening site as the fermentation field. After it is cleaned, a layer of lime is sprinkled on the ground for disinfection. (ii) Building a heap. After the culture material used in the raw meal cultivation method absorbs enough water by spraying, to which 5% wheat bran is added. The culture material is piled into a trapezoidal pile with a bottom width of 2 m, a top width of 1.2 m, a height of 0.8 m and an unlimited length. Water overflows around the stockpile but does not flow out. Holes should be punched at the top and around the material for ventilation to facilitate ventilation and fermentation. A thermometer is placed 20 cm away from the ground and the top surface. It is inserted into the material with a depth about 10 cm and is parallel to the ground. (iii) Turning the heap. After the pile is built, the pile temperature is recorded every day. After the highest temperature lasts for 3 d, the pile is turned for the first time. The outer cultivation material is turned into the open space in front of the pile, and then the cultivation material in the inner high temperature area is turned to the surface of the new pile. If the water content of the culture material is low, it can be properly supplemented with water. Generally, the culturing material can be completely fermented after 2-3 times of turning. The fermentation time is greatly affected by temperature, and it generally takes about 20 d[1].

Cultivation material formula: formula 1: 33% of mixed sawdust, 33% of straw, and 34% of chaff. After the cultivating material is mixed fully, it is immersed in 5% quicklime water for 24 h, and then it is piled for 15 d[2]. Formula 2: 30% of sawdust, 40% of wheat straw, and 30% of leaves. Formula 3: 30% of mixed sawdust, 30% of rape straw, and 40% of weeds[3]. Formula 4: 60% of straw, 30% of corncob, and 10% of mixed sawdust. Formula 5: 50% of straw, 40% of corn stalk, and 10% of mixed sawdust. After the above materials are mixed according to the formulas, they are stired well, to which 3% quicklime water is added and mixed well (mass ratio 1∶1). The cultivating material is sterilized at normal pressure at 100 ℃ for 10 h[4].

4.2 Site selectionIn fields, it should be cultivated in the plots with good water sources, rich soil organic matter and good granule structure. The land should be ploughed, leveled, and irrigated once. High-efficiency, low-toxicity and low-residue pesticides are used to sterilize the environment and prevent insects.

For under-forest cultivation, it should be cultivated in pine forests, fir forests or other evergreen forests with a flat terrain and a woodland canopy density of more than 0.7. Too low canopy density and too strong sunlight are not conducive to the growth of the mushroom, and it is easy to cause the pileus to crack and affect the quality. The absence of scattered light irradiation also affects the formation of the fruiting body ofS.rugosoannulata[5]. At the same time, in order to take into account the needs of land for recuperation and picking in the later period, forest land with sufficient space, close water source, and convenient drainage and irrigation should also be selected. In forest land without existing water sources such as rivers and lakes, it is sometimes necessary to drill wells and build new canals to obtain water. In orchards, bamboo forests and on other flat understory ground, drainage ditches need to be dug to allow the excess water to drain.

4.3 Soil preparationDuring field cultivation, the leveled land is made into a border bed with a height of 10-15 cm and a width of 90-100 cm. The border bed is high in the middle and slightly lower on both sides; the length is not limited. The interval between the border beds is 40 cm, and the drainage ditches with a size of 40 cm×40 cm are dug around the field.

For under-forest cultivation,S.rugosoannulatashould be cultivated along the gaps between the trees. During soil preparation, a ditch, which is 1 m wide and 0.1 m deep, is dug at the gaps between the trees. After stones, garbage and other debris are cleaned up, it is properly leveled, and some topsoil excavated is piled up on the edge of the border bed for use when covering soil. It is also possible to build the mushroom bed in the middle of the two trees or slightly close to the side of the border bed without turning the soil for leveling, which is convenient for the later fruiting management. After the mushroom bed is arranged, the site needs to be disinfected, namely sprinkling 1% "mushroom ecological treasure" or lime water on the border bed to sterilize the soil and remove insects[5].

When it is cultivated in a greenhouse, a border bed should be built according to the direction of the greenhouse. The width of the border bed is 50 cm, and the height of the border bed is 30 cm. The width of the working road between two border beds is 40 cm, and sprinkler irrigation facilities are pre-installed on the border bed surface.

4.4 Sowing and earthingIn fields,S.rugosoannulatais sown by the method of "two-layer material and one-layer strains". It should be sown in a field with a clean water source and convenient irrigation and drainage. The material border bed is 18-20 cm in hieght and 45-50 cm in width, and the length depends on the field. There is a 50 cm working road between the borders. The material border runs from the water inlet to the water outlet of the paddy field to ensure smooth irrigation and drainage of the working road. When sowing, the strains ofS.rugosoannulataare broken into pieces like pigeon eggs, but crumbs should not be produced as far as possible. The strains are sown according to the 10 cm×10 cm row spacing, which is covered with 5-8 cm of material. The border bed is made into a turtle-back shape to avoid water accumulation on the border aurface. The soil on the aisle of the border bed is dug up and covered on the border bed until the thickness is 3-5 cm. The base of the border bed is 8-10 cm higher than the working road, and a water-storage irrigation ditch is naturally formed. After 30 d of sowing, the border bed is basically full of mycelium, and it can be covered with 5 cm thick straw or rice husk. In order to prevent the mycelium from being damaged by high temperature, a layer of shade net can be covered on the straw[2].

The amount of raw material for cultivation is 3 000 kg/667 m2, and the amount of processed material is 4 000 kg/667 m2; the amount of strains is generally 500-750 g/m2. When temperature is high, the amount of stains should be increased accordingly to inhibit the growth of miscellaneous bacteria and try to avoid miscellaneous bacteria pollution[1].

For under-forest cultivation,S.rugosoannulatais sown by the method of "three-layer material and two-layer strains". Following the mountain trend, it is sown from top to bottom. The small shrubs and weeds in the forest are removed, and the cultivation material is piled into a material border which is 40 cm wide and 12 cm high. The strains ofS.rugosoannulataare broken into pieces like pigeon eggs (crumbs should not be produced as far as possible). The strains are sown according to the 10 cm×10 cm row spacing, and then covered with 8-10 cm thick cultivation material. The second layer of strains is sown as above, and then covered with 5 cm thick cultivation material. The border surface is made into a turtle-back shape. 30-40 d after inoculation, the cultivation material is opened and observed. When the mycelium acounts for two-thirds of the material, it can be covered with soil. The covering soil can be humus soil rich in organic matter in the forest. It is required that the diameter of the covering soil particles is 1-2 cm, and the thickness of the covering soil layer is 3-5 cm. After soil covering, the surface of the soil can be directly covered with weeds, straw or understory leaves, and pine needles with a thickness of 3-5 cm[3].

4.5 Cultivation managementAfter sowing, the temperature of the culture material should be kept at 20-30 ℃, preferably around 25 ℃, so that the mycelium grows fast and robust. If the heap temperature is too high, it should be reduced by removing the cover, punching the middle of the border, enlarging the shade. From sowing to mycelium growing over the border bed, moisture management is the key point of the entire production. The moisture of the cultivation material should be kept at 75%, and the relative air humidity should be kept at 75%.

S.rugosoannulatais resistant to waterlogging and aerobic. In the growth stage of mycelium, the contradiction between water and oxygen should be adjusted, and it can be balanced by controlling the water storage capacity of the working road in field cultivation. On the 2ndday after sowing, water is stored in the working road, and the water depth is 26-30 cm; the water surface is just equal to or slightly lower than the border bed height, and it is maintained for 1-2 d. On the 5thday, the water depth is reduced to 20-25 cm, and is maintained for 10 d. From the 15thto 30thday, the water level gradually decreases to the base of the border bed until mycelium graws in the soil at the base.

4.6 Fruiting managementGenerally, after about 30 d, the cultivation material is covered with mycelium. After 1-2 weeks, the mycelium grows out of the soil, and fruiting management can be started. The key is to keep moisturizing and strengthening ventilation. It is necessary to spray on the border bed every morning and evening, and spraying should be moderate and frequent, but it should not be sprayed with large amounts of water, so as to keep the relative air humidity at 80%-95%. More water is sprayed on sunny days, while less or no water is sprayed on cloudy and rainy days, so as to avoid the death of young mushrooms. During the fruiting stage, the mushroom body needs more light, but the proportion of the shade should be 50%-80% during the growth period of the fruit body. If the light is too strong, the color of the mushroom body will turn white in the later stage of growth, and it will cause certain damage to the mycelium of the fungus bed.

When the water storage channel is used to control the humidity, after the mushroom buds are found, the water storage depth of the working road is increased to 25 cm, which is maintained for 1 h, and then the water is drained. The operation is repeated once a day. After 1-3 d, the fungus buds grow into mushrooms. Generally, it can be harvested 3-5 d after the primordia appears.

4.7 Harvest and time interval managementWhen the white spots on the surface of the pileus ofS.rugosoannulataare gradually reduced until diaappearing and the fungus membrane is about to be broken, it can be harvested. The stipe is held with the thumb and forefinger, and rotated gently to separate the base of the stipe from the mycelium in the material; the mushroom body is gently pulled out, and the mycelium on the border surface should not damageed as far as possible. After the mushroom body is pulled out, the small hole left by the mushroom harvesting is gently backfilled with the soil covering the border surface. After harvesting, the soil at the foot of the mushrooms is removed in time, and the mushrooms are packed for fresh sale or sliced and dried. The mushrooms are dried at about 45 ℃, and dehumidified with strong wind to fix the shape of the mushrooms . After the shape and color of the mushrooms are stable, the temperature is raised to 60 ℃ to dry the mushroom body.

Generally,S.rugosoannulatacan be harvested 4 times in one production cycle, and the time interval between two harvests is about 25 d. The key points of the harvest time management technology ofS.rugosoannulataare "resting, watering thoroughly, and moisturizing". After the mushrooms are harvested, the surface of the border bed is cleaned to let the mycelium grow back for 2-3 d. Afterwards, the entire border bed is irrigated by drip irrigation or sprinkling irrigation, and there is water flowing out from the edge of the border bed. The moisture content of the border bed and relative air humidity are kept at above 85% until the next mushrooms grow.

5 Summary

To sum up, there is still a lot of room for improvement in the cultivation techniques ofS.rugosoannulata. On the basis of clarifying the planting status and planting goals, it is necessary to grasp the current cultivation points, so as to improve the cultivation techniques and economic benefit ofS.rugosoannulata, realize the stable and high yield ofS.rugosoannulata, and promote the development and progress of the industry.