What are the latest propagation methods for monk fruit?
Monk fruit (Siraitia grosvenorii) is a perennial vine of the Cucurbitaceae family, hailed by people as the “immortal fruit.” It blooms in summer and fruits in autumn. In China, it is mainly produced in Longjiang Township, Longsheng, and Baishou towns of Yongfu County, Guilin City, Guangxi Zhuang Autonomous Region. Its propagation methods mainly include vine layering, grafting, and seed propagation, with vine layering being the primary method used in production. Let's take a look at the propagation methods of monk fruit!
Monk Fruit Vine Layering Propagation
1. Layering time: This depends on local climatic conditions. Generally, it is suitable when the ten-day average temperature is 25-28°C, that is, from White Dew to the Autumnal Equinox.
2. Material selection: Choose the drooping, rampant vines on the trellis that have vigorous growth, are thick and strong, have long internodes, small leaves, rounded tips, and light green color. For superior plants that bear many fruits but have no rampant vines, layering propagation cannot be carried out that year. In early spring of the following year, let part of the vine trail along the ground to encourage rampant growth and thickening, forming good layering material. To speed up propagation, tubers planted that year can be kept from climbing the trellis and allowed to trail on the ground, with timely pinching to promote lateral vine growth and cultivate layering material.
3. Layering methods
① Layering in place: Layering in place means digging a pit near the layering material to perform layering. According to the amount of layering material, determine the width of the pit. Generally, for one vine or 3-4 vines, dig a pit 25 cm long, 10-20 cm wide, and 10 cm deep on the bed. Guide the vine into the pit, place the tip of the vine at 2/3 of the pit, with each vine 3-4 cm apart. Then gently cover with fine soil 3-4 cm above the bed surface, cover with rice straw, water, and keep the soil moist to promote new root growth and tuber expansion.
② Air layering: Air layering, also called off-soil layering, uses moss as the growing medium. Take a piece of plastic film 20 cm long and 25 cm wide, spread moss 3 cm thick on it, place the tip of the selected layering material at 2/3 of the moss, then roll and wrap the vine into a cylinder shape, tie both ends with rope, and place it in a shady spot on the trellis, avoiding direct sunlight. After 50-60 days, around the Start of Winter, cut it off from the base of the tuber, and bring the wrapped tuber indoors for storage over winter until use.
Monk Fruit Seed Propagation
1. Seed collection: During the monk fruit ripening season, select robust, high-yielding, pest-free plants from superior varieties as mother plants for seed collection. Choose plump fruits with the characteristics of the variety as seed stock, and harvest when the fruit stalk turns withered yellow and the fruit skin turns yellow.
① Fruit storage of seeds: Monk fruits used for seed should retain the fruit stalk and keep the skin undamaged. After harvesting, first soak in a 500-fold diluted Topsin solution for 10 minutes to disinfect and eliminate pathogens on the fruit surface, then hang in a ventilated place to dry. This method is beneficial for seed after-ripening, and the seed germination rate can reach as high as 70-80%.
② Bag storage of seeds: For harvested fruits, first remove the fruit skin, put into a linen bag, wash clean in clear water, select the seeds, dry indoors, then store in bags until use. However, seeds preserved this way have a lower germination rate than fruit-stored seeds.
2. Germination promotion and disinfection: Monk fruit seeds are germinated in early spring when the ten-day average temperature stabilizes above 15°C. The seed shell is hard, and if the shell is not removed before germination, it is very difficult for water to be absorbed, germination is very slow, and it is uneven. For this reason, during germination promotion, use a single-edge blade to make a light cut at the side suture of the seed, pry open the seed shell and take out the seed kernel, and select plump seed kernels for germination. Before germination promotion, disinfect the seed kernels by soaking in a 500-fold diluted Topsin solution for 8-10 minutes, then rinse with cold boiled water or distilled water and prepare for germination.
3. Seedbed preparation: For the monk fruit germination bed, use bamboo or wooden containers filled with fine sand 8-10 cm deep. Place the seed kernels on the sand surface at a spacing of 2×3 cm, then cover with fine sand 0.5 cm, keep the germination bed moist, and cover with plastic film. Keep the germination bed at 25-28°C; in 5-6 days, they will sprout.
4. Sowing and transplanting: Monk fruit seeds germinate very unevenly. To cultivate strong seedlings, transplant the first-germinated seedlings to the seedbed for intensive management. The seedbed can use decomposed manure soil (disinfected) mixed with 1/3 fine sand. Make beds 1.2 m wide in cultivated land and level the bed surface. Transplant seedlings with cotyledons open or half-open into the seedbed at a spacing of 10×12 cm. After transplanting, water with settling water and keep the bed soil moist. Seedlings can also be transplanted into nutrient cups made of a 1:2 mixture of garbage soil and loess for later transplanting and field planting.
5. Temporary planting method: When seedlings grow 5-6 true leaves, they can be temporarily planted. Temporary planting is mainly for identifying male and female plants, so the plant density is relatively high, with a spacing of 1×1 m. Dig pits 40×30×30 cm in length, width, and depth, backfill with mature soil and basal fertilizer, and plant two plants per pit. Strengthen seedling management to promote early flowering, which facilitates identification of male and female plants. After flowering and confirming male and female plants, carry out final planting.
6. Seedling management: Given that monk fruit fears both strong light and drought, during the seedling stage, shade should be provided during the hot sunny season and frequent watering should be done to prevent drought. Pay attention to applying diluted decomposed human manure, or use 0.5% urea solution to water the roots to promote seedling growth. At the same time, pay attention to pest and disease control.
Monk Fruit Grafting Propagation
1. Rootstock cultivation: Select highly adaptable varieties such as Qingpiguo, Chashanguo, and Hongmaoguo, and cultivate rootstock using vine layering or seedling propagation methods. Rootstock cultivated by vine layering has tubers that grow quickly and can bear fruit earlier after grafting. The seedling propagation method for rootstock has the characteristics of robust plants, well-developed root systems, and a high propagation coefficient, and can be used for large-scale grafting.
2. Scion selection: From superior varieties, select the middle portion of semi-lignified vines with large leaves, short internodes, thick stems, and no pests or diseases as scions. Cut off the 3-4 too-tender nodes at the vine tip, take 8-10 nodes with plump buds from the middle portion of each vine, and cut off 2/3 of the leaves. Insert into a bucket of water or temporarily wrap with a moist towel for later use.
3. Grafting time: To allow grafted seedlings to flower and fruit in the same year and form thick main vines before overwintering for safe winter survival, grafting in the first half of the year is best. Experiments have shown that monk fruit has the highest grafting survival rate in early June when growth is most vigorous. Choose windless, warm sunny days or cloudy days; avoid high temperature, dry, rainy, or hot midday conditions.
4. Grafting methods: There are many grafting methods for monk fruit. Commonly used are the side-veneer graft and the splice graft, which have the advantages of high survival rate, easy splitting of rootstock and insertion of buds, large contact surface between rootstock and scion, and good healing of the union, but the rootstock must have its buds removed promptly.
① Side-veneer method: Use single-bud side grafting, centered on the axillary bud, use a blade to peel off the bark layer, leaving 1.5 cm on each of the upper and lower ends, and cut both ends into wedge shapes. At 10-15 cm from the base of the rootstock, select an internode with a curvature similar to the scion. Centered on the internode, make a longitudinal cut from top to bottom, with a cut length of 3 cm. The cross-section of the cut should equal the width of the scion. The cut should be smooth, shallow at both ends and slightly deeper in the middle. When inserting the scion, align the bark layers of the rootstock and scion. After cutting the scion and splitting the rootstock, insert promptly, align the bark layers of the rootstock and scion, and ensure the bud is not placed sideways to improve the survival rate.
② Splice method: Use a single-bud scion. When cutting the scion, center on the bud, make a longitudinal cut on the opposite side of the bud, 3 cm long, leaving 1.5 cm on the front side of the bud, and cut both ends into 45-degree bevels. At 10-15 cm from the base of the rootstock, select a relatively straight internode, use a blade to make a cut upward and downward, with a cut length of 3.5 cm, and peel off a 0.8 cm bark layer in the middle of the cut to expose the scion bud. Align the cut of the scion with the cut of the rootstock and insert, taking care to align the bark layers on both sides of the rootstock and scion. If the scion is smaller than the rootstock, align it to one side.
③ Side grafting method: Use single-bud grafting. Make an oblique cut below the bud on each side, with a cut of 2 cm, forming a wedge shape. Above the internode of the rootstock, near the bud side, make a longitudinal cut from top to bottom, 2 cm long, then insert the scion into the rootstock cut, so that the bark layers fit tightly, and wrap.
④ Cleft grafting method: Use single-bud grafting. Cut the scion on both sides below the bud, with a cut of 2 cm, forming a wedge shape. Cut off the rootstock at 10-15 cm above the ground, make a longitudinal cut from the center of the cut surface with a blade to split it open, with a cut length of 2 cm. Insert the scion into the cut, align the bark layers of the rootstock and scion. If the scion is smaller than the rootstock, place the scion close to one side of the rootstock to align the bark layers, and wrap tightly.
5. Wrapping and unbinding: After inserting the scion into the rootstock cut, use a 0.5 cm wide synthetic fiber binding tape to wrap from bottom to top, coil over coil, up to the upper cut. When the scion bud shoot grows about 30 cm, loosen the binding tape. To concentrate nutrients for the new scion shoot, promptly remove new buds on the rootstock.
6. Protecting vines through winter: To protect the grafted main vine of monk fruit through winter safely, in areas with frost, after monk fruit harvest, the tender vines gradually die. Before the Start of Winter, cut the main vine at 1.5 m above the ground, and apply wax to the cut to prevent dieback. Use rice straw to wrap and bundle the main stem, or use nylon film bags for insulation, or bend the main vine and bury it in soil for warmth. However, the soil must be fine and crumbly, and the humidity should not be too high, to prevent rot.