The new technology of watermelon hybrid seed production
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In the production of hybrid watermelon seeds, careful planning and precise execution are essential to ensure high-quality results. First, the crop rotation system must be carefully selected. Fields that have not been used for Cucurbitaceae, Solanaceae, or tobacco crops in recent years are ideal for planting corn, alfalfa, wheat, or legumes. The soil should be loamy, rich in organic matter, and have a neutral pH. It is also important to keep the farming area at least 500 to 1,000 meters away from melon fields to avoid cross-pollination.
Next, the selection of parent seeds is crucial. The parent seeds must meet strict quality standards, with a purity of at least 99.7% and a germination rate of no less than 90%, as per national seed regulations. Parent seeds are categorized into large, medium, and small sizes, with specific amounts required per 667 square meters. For example, large seeds require about 0.3–0.35 kg, while small seeds need 0.1–0.15 kg. The male parent seeds are generally around 20 grams per 667 square meters, and the ratio of male to female seeds should be 1:20.
Planting typically begins in northern Xinjiang during spring when the soil temperature at 5 cm depth stabilizes above 15°C, usually between late April and early May. The male parent should be sown 7–10 days earlier than the female to ensure synchronization during flowering. Plant spacing varies depending on the variety—large-fruited females may be broadcasted, while smaller ones are more densely seeded. Male plants are placed on separate ridges with 20–30 cm spacing. Seeds are sown in holes on plastic mulch, with 1–2 seeds per hole and a depth of 1.5–2 cm. A small amount of insecticide like carbofuran is added to each hole to protect against underground pests. After sowing, the seeds are covered with fine dry soil to ensure good contact with the ground.
Thinning and pruning are essential steps after emergence. When seedlings have 3–4 true leaves, one plant per hole is kept, and missing plants are replaced with two. For male parents, two to three vines are allowed per plant, while side branches are removed. Female parents should have only one main vine, with all other shoots pruned. Male flowers are retained for pollination, while female flowers are left to receive pollen. Pruning should be done on sunny days to prevent disease spread, and tools should be disinfected with alcohol and trisodium phosphate before use.
Artificial cross-pollination is a critical step. During the male parent's flowering period, any plants showing mixed traits are removed to maintain purity. Pollination occurs when female flowers open, typically between 6:30 AM and 11:00 AM, when temperatures are around 22–24°C. Female flower buds are capped with red paper the day before to facilitate controlled pollination. Male flowers are collected early in the morning and stored in cool, sealed containers. Each male flower can pollinate 2–3 female flowers. After pollination, the female flowers are covered with paper caps, and the pedicels are tied to confirm successful cross-pollination.
Once the fruit reaches egg size, the pollination process stops, and all non-pollinated fruits are removed. The entire field is then cleared of parent plants to prevent unwanted cross-pollination. Cross-pollinated fruits are marked again when they reach bowl-mouth size to ensure uniform development and proper identification. Any unmarked or irregular fruits are removed to prevent contamination.
Harvesting occurs once the seeds inside the fruit are fully mature. Fruits with abnormal shapes, colors, or signs of disease are discarded. Hybrid fruits are carefully broken open, fermented, and cleaned to extract the seeds. Fermentation helps remove mucus and improve seed viability. After washing, the seeds are dried on plastic screens, avoiding direct sunlight or metal surfaces that could damage them. Drying continues until moisture levels reach 8%, meeting national standards.
Seed disinfection is performed using a 1:80 solution of disinfectant and water, with seeds soaked for 15 minutes. After drying, seeds are stored in labeled bags and kept in dry conditions. Quality checks include field and lab testing for purity, germination, moisture, and clarity, ensuring compliance with national standards.
Throughout the process, attention must be given to common diseases such as damping-off, blight, and powdery mildew, as well as pests like aphids and whiteflies. Integrated pest management strategies involving biological, physical, and chemical methods are essential to maintain healthy seed production.