How is sexual propagation of the Chinese medicinal herb yellow ginger carried out for large-scale seedling production in greenhouses?

Yellow gingerIts scientific name is Dioscorea zingiberensis C.H.Wright (Dioscoreaceae), and it contains diosgenin sapogenin, commonly known as saponin genin or saponin (hereinafter referred to as saponin). It is an ideal plant for extracting diosgenin and is known as "medicinal gold." Growing yellow ginger offers relatively high economic returns and has developed rapidly across the country. Many counties and townships have established yellow ginger production bases and treat yellow ginger cultivation as a pillar industry to drive local economic development, with the scale of development rising in a straight line. Conventionally, it is propagated asexually by rhizomes, which requires a large amount of seed material and has high costs. Moreover, the rapid development of yellow ginger has led to problems such as a serious shortage of seed sources, mixed varieties, and declining yields. Using sexual propagation is one of the better ways to solve the above problems.

1 Materials and Methods

1.1 Cultivation of sexual seeds

Establish a seed cultivation base of 1 hectare. Introduce and collect high-quality resources from Shimen and Anhua in Hunan; Neixiang County in Shaanxi; Lijiang and Honghe in Yunnan; and Fang County, Yunxi, Yichang, Changyang, and Yuan'an in Hubei, and plant them mixed in the seed cultivation base to allow natural pollination. In terms of management, focus on promoting the formation of flowers, fruits, and seeds to ensure seed quality and quantity. Therefore, when sowing in the seed collection garden, apply additional organic fertilizer and nitrogen-phosphorus-potassium compound fertilizer. The trellis strips should be above 1.8 m. At the initial flowering stage, spray a mixed solution of 0.2%-0.4% monopotassium phosphate and 0.1%-0.25% borax; spray once every 7-10 days for a total of 3 sprays. When the leaf color is relatively pale, additionally spray 0.3%-0.4% urea plus seaweed fertilizer at 800 times dilution. Promptly thin out weak flowers and weak fruits on female plants to ensure seed quality.

1.2 Seed harvesting and treatment

The sign that yellow ginger seeds are mature is that the fruits are plump, and the capsules change from green to blue and finally to black-blue, and are relatively hard, while the winged seed kernels inside appear brown-yellow; at this point, harvest the capsules. Harvest according to local and seasonal conditions. Because the yellow ginger in the seed garden is a heterozygous population and does not mature uniformly, harvest in batches. After picking out the leaves from the harvested capsules, spread them in a ventilated, cool place to air-dry for one week. To prevent the capsules from heating up and becoming moldy and deteriorating, the spreading thickness should not exceed 20 cm. Wait until the capsules have completely turned blue-black, then sun-dry them. After they split open, gently turn and tap them so the seeds fall off naturally.

In mid-December, take the harvested and sun-dried seeds and first disinfect them with a 1000-fold aqueous solution of 25% carbendazim wettable powder for 12 h. Remove them and rinse clean with 30°C warm water, then soak them in 30°C warm water for 10 h, stirring continuously during soaking. Remove shriveled seeds and insect-damaged seeds, then remove and air-dry. Next, soak them with 10 mg/L GA for 24 h, then remove and drain the seeds. Finally, treat them by sand storage for 20-30 days, with the temperature controlled below 2-5°C and the humidity maintained at about 50%.

1.3 Seed germination

The size of the germination room is determined according to the scale of germination. Generally, for a capacity of 80 kg of seeds per batch, the germination room requires an area of 20 square meters and must be light-proof, ventilated, and insulated. It also requires matching germination trays, and then matching germination racks should be built. Place the seedling trays on the germination racks, strictly control temperature, and leave ventilation holes in the germination room.

Start germination in early January. Before germination, disinfect the germination room and supporting equipment with 800-fold 25% carbendazim solution. Then evenly spread sterilized sawdust into the trays, and then evenly scatter the treated seeds into the trays. The area is 3500 cm2, using 1 kg of seed per tray, about 80,000 seeds. Place them in the germination room for germination. Control the temperature at 25-30°C for the first two days, then maintain it at about 25°C, keep relative humidity above 80%, and maintain light-proof conditions and uniform ventilation. Germination begins in 7 days, 50% germination occurs in 10-12 days, and when germination reaches more than 80% in 13-15 days, sowing can begin.

1.4 Greenhouse seedling cultivation

One month before sowing, prepare nutrient soil at 90 cubic meters per hectare, using 70% fine sandy soil, 10% plant ash, 20% decomposed organic fertilizer, and 5 kg of high-efficiency compound fertilizer per cubic meter. Mix thoroughly and evenly, then compact it, cover it well with plastic film, and set aside for use.

Half a month before sowing, deeply plow the greenhouse seedling bed soil to 30 cm and make beds 1.2 m wide and 0.2 m high. Level and finely break up the bed surface. Evenly spread sieved nutrient soil onto the bed surface to a thickness of about 2 cm, then spray and disinfect with 800-fold 25% carbendazim solution, and water thoroughly one week before sowing. Sow in mid-January. The sowing method is to open shallow furrows horizontally on the bed surface, with a furrow depth of 2-3 cm and a row spacing of 15 cm. Evenly broadcast the germinated seeds into the furrows and cover with 2 cm of sieved nutrient soil. In addition, plant seeds with sprouts longer than 2 cm into the furrows at a spacing of 2 cm.

After sowing, attention should be paid to keeping the bed surface moist. Maintain the temperature inside the greenhouse at 20-28°C, and maintain the temperature by uncovering and covering the film. When the temperature is relatively low, build another small tunnel inside the greenhouse. Keep relative humidity above 80%. Seedlings begin to emerge about 15 days after sowing. After about 30 days, 1-2 complete leaves can grow. At this time, ventilate the greenhouse frequently. From 50 to 60 days after emergence, that is, in early April, uncover the film to harden the seedlings. About 3 months after emergence (late April), when most yellow ginger seedlings have grown 3-5 complete leaves, they can leave the nursery. During seedling hardening, if there is a lot of rain, spray 800-fold 50% Xinling solution to control yellow ginger diseases, and use Chongduosha to control cutworms. Keep the seedling bed free of weeds.

1.5 Transplanting seedlings

In late April and early May, when the seedlings have grown about 3 leaves, they can leave the nursery and be planted in the field. When lifting seedlings, keep the roots undamaged and carry as much soil as possible, then transport them in seedling trays or cardboard boxes. Choose a sunny day for planting. The planting depth depends on seedling size and is generally 2-3 cm. After planting, water thoroughly to settle the roots.