Detailed Explanation of the Bag-Cultivation Technique for Sexual Propagation of Gastrodia elata

Gastrodia elata is a precious traditional Chinese medicinal herb, a perennial herbaceous plant of the Orchidaceae family, with no roots and no green leaves, mainly obtaining nutrients by digesting fungi such as Armillaria mellea that invade its body. It contains vanillyl alcohol, vanillin, glycosides, vitamin A-like substances, crystalline neutral substances and trace amounts of alkaloids as well as mucilage, and has the effects of tonifying qi and nourishing the liver, calming fright, extinguishing wind and stopping spasms. The history of artificial cultivation of Gastrodia elata is not long, but cultivation techniques have developed rapidly. In the past, artificial cultivation of Gastrodia elata generally used asexual propagation, and the seed tubers degenerated generation by generation, with low and unstable yields, greatly affecting production. Sexual propagation of Gastrodia elata is an effective method to overcome variety degeneration. Sexual propagation of Gastrodia elata is also called seed propagation, that is, cultivation and propagation using the seeds set after flowering and pollination of arrow tubers. The bag-cultivation technique for sexual propagation of Gastrodia elata can make better use of space, save costs, reduce labor intensity and improve labor efficiency, and can solve the problems of field sowing requiring a large propagation site, being easily affected by environmental factors such as temperature and humidity, and being difficult to manage. The bag-cultivation technique for sexual propagation of Gastrodia elata is introduced as follows:  

1 Preliminary work preparation  1.1 Pollen and seed cultivation The length of growth time and size of the underground tubers of Gastrodia elata are classified by appearance into arrow tubers, white tubers, rice tubers, mother tubers and large white tubers. Arrow tubers and large white tubers can both be used as medicine, also called commercial tubers. Arrow tubers can grow aboveground stems and can flower and set seeds. When it bolts, the stem resembles an arrow, hence the name arrow tuber. Select fresh, robust arrow tubers without damage, mildew or rot, and free of pests and diseases, with a tuber weight of about 100-200 g as seed. Arrow tubers must be dug from the Beginning of Winter to before seedling emergence in spring. The survival rate of spring planting is significantly higher than that of winter planting. Because the arrow tuber itself stores abundant nutrients that can meet the needs of bolting, flowering and fruiting, it is not necessary to plant it with fungal wood, and indoor cultivation is generally used. For outdoor cultivation, a rain-shelter shade shed should be built and attention should be paid to wind protection; in dry weather, water should be applied in time to keep the soil moist. Measures such as pinching off the tips and artificial cross-pollination between different plants and different flowers can significantly increase the fruit set and single-seed weight of arrow tubers. It should be noted that for Gastrodia elata fruits, the germination rate differs greatly between harvesting after ripening and before dehiscence. Picking dehiscent fruits and mature tender fruits and sowing them in time is an important measure to ensure a relatively high germination rate. The signs of fruit maturity of Gastrodia elata are: 1) the fruit changes from hard to soft when touched by hand; 2) the fruit suture has not split and appears white and shiny; 3) the seeds scatter when the fruit skin is peeled open. Seed storage must absolutely avoid exposure to sunlight. The storage time at natural environmental temperature has a great impact on seed germination rate. Seeds harvested before natural dehiscence of the fruit can reach a germination rate of 94%; on the day of natural dehiscence of the fruit, the seed germination rate drops to 88.4%; after storage at room temperature for 3 d, the germination rate drops to 22.3%. After harvesting, Gastrodia elata seeds should be sown as soon as possible, preferably harvesting and sowing at the same time. If they cannot be sown immediately, the seeds should be placed in glassware or put into paper bags and stored under low-temperature conditions of 3°C-5°C in a refrigerator, and sown within half a month to ensure the germination rate.  1.2 Mixing seeds with germination fungus For the germination of Gastrodia elata seeds, a germination fungus is needed for companion sowing, and companion sowing with Mycena purpureofusca gives a relatively high germination rate. Before sowing, take out the already cultured secondary spawn of Mycena purpureofusca germination fungus or the tertiary leaf cultivation spawn from the culture bottle, put it into an enamel basin that has been cleaned and disinfected, use one bottle of spawn per bag, break the secondary spawn into pieces the size of walnut kernels or separate the sticky fungus leaves one by one for later use. Shake the seeds of mature tender fruits and near-dehiscent fruits of Gastrodia elata out of the capsules, gently sprinkle them on the spawn blocks (leaves), mixing while sprinkling. The seeds should be sprinkled in multiple batches, and after sprinkling, mix evenly again, so as to avoid the seeds concentrating on a small number of spawn blocks or fungus leaves, which would affect inoculation and germination. The sowing amount should not be too large or too small; sow 5-7 plump capsules per bag. After the germination fungus is evenly mixed with the powdery seeds inside the capsules, cover the basin with clean newspaper or plastic film and place it in a leeward, shady and moist place. After 24 h, when a layer of white hairy aerial hyphae grows on the spawn blocks (leaves) and completely covers the seeds, then bag them. In this way, after the Gastrodia elata seeds combine with the Mycena purpureofusca germination fungus, the germination rate is high and growth is fast.