Potato virus-free seed breeding technology is a critical approach to enhancing potato yields and ensuring high-quality production. The quality of the seed potatoes directly influences the success of field cultivation. Therefore, maintaining the genetic purity of virus-free seed potatoes and preventing viral infections and variety degeneration are essential in producing superior seed stock.
1. **Preparation of Original Seed Stock**
To ensure high-quality virus-free seeds, it is important to select high-purity, detoxified seed potatoes from specialized units that produce virus-free materials. These potatoes should be of 20–30 grams in weight, free from insect damage, cracks, or sprouting, with smooth skin and uniform size. Approximately 90–120 kg per mu is required for planting. Whole tubers must be used, and mulching techniques are not recommended during sowing.
2. **Selection of Breeding Sites**
Breeding areas should be located in cool, humid, and well-ventilated regions, preferably on flat terrain without nearby cruciferous crops. The site should be isolated from other potato varieties to prevent cross-infection. Soil should be fertile, loose, and evenly nourished. It’s crucial to avoid planting non-detoxified or mixed varieties to maintain the integrity of the virus-free seed stock.
3. **Deep Plowing**
Deep plowing improves soil structure, enhances organic matter decomposition, and increases water retention. It is typically done when soil moisture is between 40% and 60%, at a depth of 20–30 cm. This process should be combined with chemical soil treatments and applied along with base fertilizer.
4. **Balanced Fertilization**
Potatoes require rich nutrients, so organic fertilizers are essential. However, they should not contain leaves from solanaceous plants like potatoes. Virus-free seed potatoes have strong growth potential, so adequate base fertilizer and suitable seed fertilizer are necessary. A general recommendation includes 5,000 kg of high-quality organic manure, 23 kg of pure nitrogen, 4.6 kg of phosphorus pentoxide, and 26 kg of potassium oxide. During the flowering stage, top-dressing with 5–10 kg of compound fertilizer per mu or foliar spraying with 0.3% potassium dihydrogen
Phosphate solution is advised.
5. **Sowing Techniques**
5.1 **Planting Density**: Plant approximately 4,500 to 5,500 plants per mu, with row spacing of 50–65 cm and plant spacing of 25–35 cm.
5.2 **Sowing Time and Depth**: Sow when the soil temperature reaches 7–8°C at a depth of 10 cm. In Qinghai Province, this is usually between late April and early May, with a sowing depth of 8–12 cm.
6. **Field Management**
6.1 **Soil Loosening and Weeding**: Virus-free seed potatoes grow rapidly, so prompt management is necessary. Manual weeding can help increase soil temperature and strengthen seedlings. When the plants reach about 20 cm, the second earthing-up should be done before mulching.
6.2 **Removal of Diseased and Mixed Plants**: Regular inspections should be conducted during the seedling, budding, and flowering stages, as well as 20–25 days after. Diseased or mixed plants should be removed to prevent contamination. At harvest, only healthy plants should be selected, and any diseased or damaged tubers must be discarded.
6.3 **Pest Control**: Pesticides should be used to manage underground pests such as wireworms and beetles. If late blight occurs, timely spraying is necessary to control the disease.
7. **Harvesting and Storage**
Before harvesting, care must be taken to avoid frost and mechanical damage. Tubers should be air-dried for one or two days to improve storage quality. When placing them in storage, handle them gently to prevent bruising. The ideal storage temperature is 2–4°C with 80% relative humidity. Good ventilation is essential to ensure proper airflow and prevent rotting or premature sprouting. Different varieties should be stored separately, and the storage pit should be cleaned and fumigated one month before harvest. During storage, attention should be given to temperature control, moisture prevention, and avoiding mix-ups to maintain seed quality.
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