Detailed Explanation of High-Quality and High-Yield Cultivation Techniques for Log-Grown Lingzhi (Ganoderma)
Lingzhi (Ganoderma) is a precious medicinal fungus. Modern medical research has demonstrated that lingzhi possesses multiple functions such as cancer prevention, anti-cancer and anti-aging properties, and the development and application of lingzhi has attracted widespread attention. Longquan City is a key production area for lingzhi; in the early 1990s, trials of short-log sterilized-substrate cultivation techniques for lingzhi were already underway, and these techniques have been continuously refined through production extension and application. By 2002, the city's log-grown lingzhi cultivation volume reached 3000 cubic meters, with a total output of 120 tons, accounting for about 1/4 of the national total output, and achieving an output value of 7 million yuan. Longquan lingzhi has a dense texture, high content of active ingredients, and low heavy metal content, and its products sell well in Japan, South Korea and other Southeast Asian countries. In January 1996, it was awarded the honorary title of "China's First Hometown of Lingzhi" by the Development Research Center of the State Council and was included in the Grand Ceremony of China's Best; the lingzhi base construction project was awarded the first prize of the "Golden Bridge Project" by the Provincial Association for Science and Technology in 1996; and in 2002 it was designated by the Provincial Department of Agriculture as a "High-Quality and High-Efficiency Planting Production Base." In recent years, the city's lingzhi production has advanced toward industrialization, and the successful development of a series of products such as lingzhi capsules, lingzhi wine, lingzhi slices and lingzhi spore powder has provided good opportunities for the development of lingzhi production and the growth of mountain farmers' economic income. In order to rationally develop and utilize mountain resources and ensure the sustainable development of high-quality log-grown lingzhi production in mountainous areas, we have summarized the biological characteristics of lingzhi, the characteristics of log-grown lingzhi and its high-quality and high-yield cultivation techniques as follows, based on many years of production practice.
1. Biological Characteristics of Lingzhi
Lingzhi varieties are diverse and widely distributed. Its traces can be found in most provinces of China at mountain elevations of 300-600 m, especially under tropical and subtropical mixed forests. In the wild, lingzhi mostly grows in late summer and early autumn after rain on dead tree stumps or fallen trees of broadleaf forests such as oak, castanopsis and tanbark oak, and can also grow on living trees. Lingzhi has a wide temperature adaptation range and is a medium-to-high temperature saprophytic fungus and facultative parasitic fungus.
(1) Temperature. The mycelial growth temperature range of lingzhi is 3-40°C, the normal growth range is 18-35°C, the more suitable temperature is 24-30°C, and the optimum temperature is 26-28°C. The temperature range for fruiting body formation of lingzhi is 18-32°C, with the optimum temperature being 26-28°C. At 30°C, lingzhi fruiting bodies develop faster but with poorer texture and color. At 25°C, fruiting bodies develop with dense texture and good luster. When the temperature remains above 35°C or below 10°C, fruiting body development is difficult to differentiate. The optimum temperature for spore germination is 24-26°C.
(2) Moisture. The mycelium of lingzhi requires an optimum moisture content of 60%-65% in the substrate, and the mycelium in logs requires a log moisture content of 33%-48%. When logs are buried in soil, the soil moisture content is required to be 16%-18%, while during the fruiting period of lingzhi the soil moisture content is required to be 19%-22%. During the mycelial growth stage of lingzhi, the relative air humidity is required to be 70%-80%, and during the fruiting body formation stage, the relative air humidity is required to be 85%-95%.
(3) Air. Lingzhi is an aerobic fungus and requires more oxygen from the air during cultivation than ordinary edible fungi. The CO2 content in the air is required to be within the normal range. Test results show that when the CO2 content in the air exceeds 0.1%, lingzhi growth produces only stipes, or the stipes only branch without opening caps, forming antler-shaped lingzhi.
(4) Light. The mycelial growth stage does not require light; exposure to light actually has a significant inhibitory effect on mycelial growth. The fruiting body formation stage of lingzhi requires diffused light. The tube layer growth of the lingzhi fruiting body has geotropism; regardless of whether the cap grows upward or tilted downward, the tube layer usually grows toward the ground and perpendicular to the ground.
(5) pH. The optimum pH for mycelial growth in the log cultivation substrate of lingzhi is 5-6, and the optimum pH for fruiting body growth is 4-5.
2. Characteristics of Log-Grown Lingzhi
(1) Good lingzhi quality. The greatest characteristic of log sterilized-substrate cultivation of lingzhi lies in the thick, broad, brightly colored fruiting bodies rich in polysaccharides and organic germanium, giving lingzhi good quality.
(2) Relatively high bioconversion rate. Because high temperature and high pressure effectively degrade the nutrients in the logs, making them easy for lingzhi mycelium to decompose and absorb, and because high-temperature sterilization reduces the chance of contamination by weed fungi, the finished product rate and qualified product rate are both relatively high, and the bioconversion rate is relatively high. Producing 1 ton of lingzhi consumes about 25 cubic meters of logs. Each 1 cubic meter of wood can produce about 40 kg of dried lingzhi in 2 years (the drying rate of fresh lingzhi is 30%-35%).
(3) Good economic benefits. Each 1 cubic meter of wood can yield an average of 40 kg of dried lingzhi in 2 years. Calculated at 50 yuan/kg, the output value can reach 2000 yuan; after deducting costs of 750 yuan, the net income per 1 cubic meter of wood can reach 1250 yuan, and the input-to-output ratio is 3:8. Generally, each 1 mu of land can be used for bed cultivation of 20 cubic meters of lingzhi logs, yielding a net profit of 25,000 yuan in 2 years.
3. High-Quality and High-Yield Cultivation Techniques for Log-Grown Lingzhi
3.1 Selecting Good Tree Species and Spawn
The yield of lingzhi depends on the total amount of mycelium in the mushroom wood, and the total amount of mycelium is in turn related to the volume of the original wood and its nutrient content. Any tree species that can be used for growing shiitake can also be used for cultivating lingzhi. Logs should preferably be selected mainly from Fagaceae tree species, such as tanbark oak, oak, castanopsis and zelkova. Others such as maple, eucommia, bitter oak and Chinese tallow are also acceptable, but their yield and quality are inferior to lingzhi produced from Fagaceae logs. Lingzhi cultivated on oak, tanbark oak and zelkova logs shows fast mycelial growth, high yield, good color and solid fruiting bodies; lingzhi cultivated on castanopsis logs shows slower mycelial growth and later fruiting, but the fruiting bodies are thick and solid with slightly lower yield; lingzhi grown on maple and other miscellaneous trees has lighter and thinner fruiting bodies and fruits easily, with high yield in the same year. Miscellaneous trees to be felled should be selected from sunny hillsides with fertile soil.
Selecting good strains is the primary step to achieving high-quality and high-yield lingzhi. First, the genetic traits of the spawn should be good; second, the quality of spawn propagation should be good. At present, the strains commonly used in production include Shinshu and South Korea, which show wide adaptability, good stability, strong resistance to weed fungi and contamination, large and well-formed fruiting bodies, high rate of first-grade products and high yield, making them ideal varieties for Longquan lingzhi cultivation. Strains such as 801, Japan No. 2, Plant Protection No. 6, Taiwan, China No. 1 and Yunnan No. 4 can also be used.