Detailed Explanation of Key Points for Bitter Gourd Grafted onto Luffa Cultivation Techniques

    After bitter gourd is grafted, the plants grow vigorously and robustly, with increased moisture tolerance, enhanced adaptability to temperature, a long harvest period, high yield, large fruits, and good quality. By selecting a suitable rootstock, grafting can provide resistance to gummy stem blight and phytophthora blight, and also has a certain tolerance to root-knot nematodes. Some management measures in bitter gourd grafting are basically the same as those for other cucurbit grafting and can be referred to; for cultivation management of grafted plants, refer to the above cultivation techniques (but the graft union must not come into contact with the soil). There are many grafting methods for bitter gourd; below only a few methods that are relatively easy to carry out in production are introduced for reference.

    1. Selection of rootstock: For bitter gourd grafting, the rootstock is generally best chosen as luffa, especially vigorous-growing long luffa. 2. Grafting methods: (1) Approach grafting: Select plump, disease-free pumpkin (or luffa) and bitter gourd seeds, and after seed disinfection, soaking, and germination promotion, sow them together in 10 cm × 10 cm × 8 cm plastic nutrition pots. At 26°C, grafting can be done after about 10 days. At this time, the seedlings have grown 1 true leaf, and the second true leaf has not yet unfolded. On the hypocotyl where the rootstock and scion face each other, 1.5 cm below the cotyledons, use a very sharp knife to lightly cut a notch about one-third or one-quarter deep into the young stem and about 1 cm long, then bring the cuts of the rootstock and scion together and secure them with a grafting clip. After grafting, maintain warmth, moisture, and shade. About 10 days after approach grafting, the union has basically healed, and the roots of the scion can begin to be cut off. Seedlings 25 or 30 days after grafting can be transplanted. (2) Tongue approach grafting: After seed soaking, germination promotion, and sowing, bitter gourd and luffa seedlings can undergo tongue approach grafting after about 10 days (when 1 true leaf has unfolded and the second true leaf has not unfolded). When grafting, lift the bitter gourd and luffa seedlings from the seedbed (taking care to damage the roots as little as possible), select seedlings of the same size and height, and at the hypocotyl 1.5 cm below the cotyledons of the bitter gourd seedling, make an upward diagonal cut about half a centimeter deep to form a tongue-shaped cut; at the corresponding position on the luffa hypocotyl, also make a tongue-shaped cut, but with the cut facing downward, also about half a centimeter deep. Then fit the cuts of the bitter gourd and luffa together, secure the joined cut with a grafting clip, and then plant the grafted bitter gourd and luffa seedlings together in a seedling pot or seedling bed. This method has a high survival rate and has been adopted by most producers. (3) Top cleft grafting: Sow luffa 5-7 days earlier than bitter gourd. When luffa has grown to 3 true leaves, remove the luffa growing point and 2 true leaves, keep 1 true leaf, and at the top of the luffa young stem, aligned between the two cotyledons, cut straight downward to a depth of about 1 cm, not splitting it completely into two halves, only splitting one side of the young stem. Remove the roots of the bitter gourd seedling, and half a centimeter below the cotyledons cut downward into a wedge shape, with the cut about 1 cm long or slightly shorter than the luffa cut. Insert the prepared bitter gourd scion into the luffa cut and secure it with a grafting clip. It can also be done when the luffa rootstock has grown 1 true leaf: remove the luffa growing point and true leaf, keep only 2 cotyledons, and between the 2 cotyledons split one side of the hypocotyl, with the cut about 1 cm long. Cut the bitter gourd scion into a wedge shape as above, then insert it into the luffa cut and secure it with a grafting clip. Top cleft grafting is easier to perform, but the survival rate is not as good as approach grafting. (4) Top cleft approach grafting: This method is similar to top cleft grafting, except that the rootstock does not retain true leaves, only retains 1 cotyledon, and the cut is made between the two cotyledons. The bitter gourd roots are not cut off; instead, 1 cm below the cotyledon node, an upward diagonal cut is made into a tongue shape, so that the tongue-shaped cut of the bitter gourd is inserted into the luffa cut, and the cut is secured with a clip, with the bitter gourd planted diagonally beside the luffa.

    This technique can effectively control soilborne diseases (fusarium wilt, bacterial wilt, etc.), result in uniform growth vigor, extend the harvest period, increase bitter gourd yield, and at the same time solve the problem of continuous cropping of bitter gourd.