In southern China, tomatoes are typically grown during spring and autumn, while in the western part of Guangdong, they can also be cultivated in winter. However, the region's high temperatures and frequent rainfall create favorable conditions for diseases, particularly bacterial wilt, which significantly affects tomato production. To address this issue, the Provincial Academy of Agricultural Sciences conducted over two years of grafting experiments, ultimately developing an efficient technique tailored for tomato cultivation in the Guangdong region.
First, the selection of rootstock and scion is crucial. Given that Guangdong is located in a tropical and subtropical zone, where bacterial wilt is prevalent, the rootstock must exhibit strong resistance to this disease. Meanwhile, the scion should be a high-quality variety that is popular in the market. In the experiment, the rootstock used was "Stock 101," and the scion was "Crown 333," both developed by the Solanaceous Research Institute. "Stock 101" is highly resistant to bacterial wilt and viral diseases, while "Crown 333" is known for its firm, high-quality fruit.
Second, timing is essential for planting. Rootstocks are sown in late January for spring planting and in early July for autumn planting. The scion should be sown about one week later than the rootstock. Using seedling trays or plug cells helps ensure healthy growth.
Third, the size and shape of the rootstock and scion matter. When the rootstock has 5–6 true leaves, it is cut 2 cm above the second leaf from the bottom, removing the growing tip. For the scion, when it has 4–5 true leaves, it is cut 1 cm below the first leaf, keeping the upper portion as the scion. Some lower leaves are removed, leaving only two leaves and the growing point to maintain stability and reduce water loss after grafting.
Fourth, there are two main grafting methods: splicing and needle connection. In splicing, the rootstock is cut at a 45-degree angle, and the scion is shaped into a wedge before being inserted into the rootstock. A graft clip is then used to secure the union. This method ensures good healing and a high survival rate. Another technique involves pulling the scion vertically into the rootstock stem. For efficiency, two people can work together—one cutting the scion, the other attaching it. To prevent dehydration, the scion can be placed in a 50% MS medium or potassium dihydrogen phosphate solution before grafting. Afterward, the grafted plants are covered with plastic film and shade nets to protect them from wind and direct sunlight.
The needle connection method is ideal when both the rootstock and scion have 2–3 true leaves. The stems are cut at a 45-degree angle and joined using sterilized needles. It’s important to ensure the cuts align properly to promote healing. Care must be taken to avoid bacterial infection, which could reduce survival rates.
After grafting, proper management is key. Within the first 3–5 days, the seedlings need protection from wind, light, and excessive moisture. In spring, the environment is more favorable, making survival easier. In summer, higher temperatures and stronger sunlight require more careful control. Shade nets, moisture retention, and controlled ventilation help maintain optimal conditions. After 5–7 days, the coverings can be gradually removed, allowing the seedlings to adjust to normal conditions.
Once the grafts have healed, the seedlings should be carefully selected for planting. The graft site should be at least 10 cm above the soil surface to prevent re-rooting of the scion, which could reduce disease resistance. Special attention should be given to disease prevention, such as spraying a bactericide like thiophanate-methyl. Moisture and light protection are also critical—especially in summer, where shading and watering techniques help keep the environment stable. Regular checks should be done to identify any failed grafts, and replacements can be made if necessary.
Using these techniques, the survival rate in spring can reach over 95%, and in autumn, around 90%. Grafted plants show increased resistance to bacterial wilt and virus diseases. However, it’s important to note that other diseases like late blight and gray mold still require conventional management practices.
This method has proven effective for improving tomato yields and disease resistance in Guangdong, and it is now widely recommended by the Vegetable Institute of the Provincial Academy of Agricultural Sciences. Researchers involved include Li Zhenxing, Sun Baojuan, and Li Zhiliang.
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