Broccoli (broccoli) breeding techniques

Broccoli is a major vegetable export crop in Zhejiang Province, with an annual planting area consistently around 10,000 hectares. However, due to the sowing season falling between July and September—when high temperatures and typhoon activity are common—it is crucial to make the most of the limited growth window to produce healthy, strong seedlings. This has become a key challenge for broccoli production, processing, and export. To address this issue, Xiangshan County's Modern Agricultural Experiment Field successfully cultivated 140 hectares of broccoli seedlings from 2001 to 2002, aiming to improve seedling quality and availability. Here’s a detailed overview of the process: **I. Environmental Requirements for Broccoli Seedling Growth** Broccoli seedlings go through three main stages: germination, basic vegetative growth, and rapid seedling development. The plant prefers cooler conditions and is classified as a semi-cold crop. Germination requires a minimum temperature of 3°C, with optimal growth between 20–25°C. Temperatures above 35°C can hinder growth. For plant development, 20–22°C is ideal, while flower buds may be damaged at temperatures below -5°C to 3°C. Early-flowering varieties can develop flower buds when average temperatures remain below 20°C. However, low temperatures during the seedling stage can lead to small, unmarketable flower bulbs. If temperatures drop below 8°C, growth slows down significantly. Late-maturing varieties require cold temperatures for flower bud differentiation, making them unsuitable for hot seasons, where they may form undesirable flower bulbs. Broccoli needs ample light but not direct sunlight. It thrives in humid conditions but is sensitive to drought and waterlogging. Water management is critical, especially during the nursery phase. The soil should be loose, fertile, and well-draining to support healthy root development. **II. Seedling Cultivation Methods** In eastern Zhejiang, open field sowing combined with shade nets and agricultural film is commonly used to manage temperature and rainfall. These techniques help protect young plants from extreme weather conditions and ensure better survival rates. **III. Standards for Strong Seedlings** Strong broccoli seedlings should be 30–35 days old, with 5–6 true leaves, robust growth, no pests or diseases, thick stems, short internodes, large and thick leaves, normal color, and well-developed fibrous roots. They should be uniform in size and appearance. **IV. Preparation of Seedbeds** 1. **Seedbed Selection**: Choose well-drained, loose soil rich in organic matter, avoiding areas where cruciferous crops were grown in the past two years. A 1:20 ratio of seedbed to field is recommended. Soil should be tilled one week before sowing, with 25 kg of compound fertilizer applied per 667 square meters. Raised beds (2m wide, 40–50cm deep) are ideal. 2. **Disinfection**: Use a mixture of 25% Lai Duomi (500 times dilution) and 40.7% Loe Si (800–1000 times dilution) to disinfect the seedbed and control underground pests. 3. **Weed Control**: Apply 70% Dole EC (20mL per 15kg water) before sowing to reduce weed competition and lower seedling costs. 4. **Soil Moisture Regulation**: Adjust soil moisture to ensure proper seed germination. The soil should be moist enough to allow seedlings to emerge without being overly wet. **V. Sowing Practices** 1. **Sowing Date**: Sowing dates vary by variety. Early varieties like Green Wind are sown mid-July to mid-August; mid-season varieties like Green Belt are sown late August to early September; and late varieties like Meilv 90 are sown mid-September to early October. 2. **Seeding Rate**: Calculate based on seed weight, germination rate, and safety factor. For example, for Green Belt, 15g per 667 square meters is recommended. 3. **Sowing Technique**: Use fine sand to mix seeds and sow evenly. Avoid covering seeds with soil; instead, mist them lightly after sowing and cover with shade netting to maintain moisture and coolness. **VI. Seedling Management** 1. **Germination and Emergence**: Monitor daily for 2–3 days. Maintain soil temperature between 25–30°C using watering and shading. Remove shade nets once cotyledons turn green. 2. **Basic Vegetative Period**: From cotyledon emergence to the 2-leaf-1-heart stage, focus on shading, irrigation, and pest control. Use shade nets from 8 AM to 4 PM, and apply fungicides like 40.7% Locust and 3% Jinggangmycin to prevent damping-off. 3. **Rapid Growth Phase**: After the 2-leaf-1-heart stage, focus on water control, spacing, and fertilization. Ensure each seedling has about 10 cm² of space and apply small amounts of urea to weak plants. Use insecticides like 5% Ruijinte and 10% imidacloprid to manage pests. **VII. Transplanting and Post-Management** Transplant seedlings with 5–6 true leaves. Two days before transplanting, apply a small amount of urea and check for pests. Ensure seedlings are well-watered and free from disease. Select uniform, strong seedlings for planting to maximize yield and quality. By following these practices, farmers in Zhejiang have been able to optimize broccoli cultivation, ensuring high-quality seedlings that meet market demands and support the province’s thriving agricultural exports.

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