Detailed Explanation of Key Points of Bag Cultivation Technology for Sexual Propagation of Gastrodia elata

Gastrodia elata is a precious traditional Chinese medicinal herb, belonging to the orchid family as a perennial herbaceous plant. It has no roots and no green leaves, and mainly obtains 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, trace alkaloids, and mucilaginous substances, and has the effects of tonifying qi and nourishing the liver, calming fright, extinguishing wind, and relieving spasms. The history of artificial cultivation of Gastrodia elata is not long, but cultivation technology has 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 species degeneration. Sexual propagation of Gastrodia elata is also called seed propagation, that is, using the seeds set after flowering and pollination of arrow tubers for cultivation and propagation. The bag cultivation technology 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 technology for sexual propagation of Gastrodia elata is introduced as follows:

1 Preliminary Work Preparation

1.1 Pollen and Seed Cultivation The growth duration 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. Both arrow tubers and large white tubers can be used as medicine, also called commercial tubers. Arrow tubers can grow aboveground stems and can flower and set seeds. When they bolt, the stems resemble arrows, hence the name arrow tubers. Select fresh, robust arrow tubers without damage, mildew, or pests and diseases, with a tuber weight of about 100-200 g, as seed tubers. Arrow tubers must be dug from the Start of Winter to before emergence in spring. The survival rate of spring planting is significantly higher than that of winter planting. Because arrow tubers themselves store abundant nutrients that can meet the needs of bolting, flowering, and fruiting, they do not need to be planted together with fungal materials, and indoor cultivation is generally used. For outdoor cultivation, a rain-sheltered shade shed should be built and attention should be paid to wind protection; in dry weather, water should be supplied 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 after the fruits of Gastrodia elata mature, the germination rate differs greatly between harvesting before dehiscence and after dehiscence. Harvesting dehiscent fruits and mature tender fruits in time for sowing is an important measure to ensure a relatively high germination rate. The signs of fruit maturity in Gastrodia elata are: 1) the fruit changes from hard to soft when touched by hand; 2) the fruit suture has not split and appears whitish and shiny; 3) when the pericarp is peeled open, the seeds can scatter. 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 fruit dehiscence can reach a germination rate of 94%; on the day of natural fruit dehiscence, 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 sowing while harvesting. When immediate sowing is not possible, 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 Fungi For the germination of Gastrodia elata seeds, germination fungi are needed for companion sowing, and companion sowing with Mycena purpureofusca gives a relatively high germination rate. Before sowing, take out the prepared secondary spawn of Mycena purpureofusca germination fungi or the tertiary leaf cultivation spawn from the culture bottle and put it into a cleaned and disinfected enamel basin. Use one bottle of spawn per bag. Break the secondary spawn into pieces the size of walnut grains, or separate the sticky fungal leaves one by one for later use. Shake the seeds of mature tender fruits and dehiscent fruits of Gastrodia elata out of the capsules and gently sprinkle them onto the spawn blocks (leaves), mixing while sprinkling. The seeds should be sprinkled in multiple batches and then mixed evenly again, so as to avoid seeds concentrating on a small number of spawn blocks or fungal leaves, which would affect inoculation and germination. The sowing amount should be neither too large nor too small. Sow 5-7 plump capsules per bag. After evenly mixing the powdery seeds from the capsules onto the germination fungi, 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, bag them. In this way, after the Gastrodia elata seeds combine with Mycena purpureofusca germination fungi, the germination rate is high and growth is fast.