Key Points of Mango Grafting and Seedling Cultivation Techniques
1. Selection of scions: Collect scions from a certified mother stock orchard or from superior individual trees of mature mother trees. The mother trees must be of pure variety, high and stable yield, good quality, and free of quarantine pests and diseases. Where conditions permit, nurseries should establish scion orchards specifically for collecting scions. Select branches from the outer periphery of the canopy exposed to sunlight, vigorous, well-developed, with plump buds, and free of pests and diseases - 1-year-old or 2-year-old mature lignified branches. Generally, autumn grafting uses current-year spring and summer shoots, while spring and summer grafting uses last year's autumn shoots or current-year spring shoots. Branches that are flowering, fruiting, or have just finished fruiting, as well as shaded weak branches, are not suitable for scions. Leaves can be removed 10-15 days in advance; after the petioles drop off, soak the collected scions in 1000 times carbendazim solution for 3 minutes, then air-dry before grafting immediately, which can improve the survival rate. Collected scions should be grafted promptly; if kept for more than 3 days, they must be stored at low temperature with moisture retention. If scions are collected from other locations, bundle them well, wrap with wet paper or wet cloth, and place in a cardboard box lined with plastic film. During transport, protect against sun exposure and heat buildup or dehydration and shrinkage.
1. Selection of scions: Collect scions from a certified mother stock orchard or from superior individual trees of mature mother trees. The mother trees must be of pure variety, high and stable yield, good quality, and free of quarantine pests and diseases. Where conditions permit, nurseries should establish scion orchards specifically for collecting scions. Select branches from the outer periphery of the canopy exposed to sunlight, vigorous, well-developed, with plump buds, and free of pests and diseases - 1-year-old or 2-year-old mature lignified branches. Generally, autumn grafting uses current-year spring and summer shoots, while spring and summer grafting uses last year's autumn shoots or current-year spring shoots. Branches that are flowering, fruiting, or have just finished fruiting, as well as shaded weak branches, are not suitable for scions. Leaves can be removed 10-15 days in advance; after the petioles drop off, soak the collected scions in 1000 times carbendazim solution for 3 minutes, then air-dry before grafting immediately, which can improve the survival rate. Collected scions should be grafted promptly; if kept for more than 3 days, they must be stored at low temperature with moisture retention. If scions are collected from other locations, bundle them well, wrap with wet paper or wet cloth, and place in a cardboard box lined with plastic film. During transport, protect against sun exposure and heat buildup or dehydration and shrinkage.
2. Grafting time: When the rootstock has been cultivated to a diameter (at 15 cm above ground level) of 1 cm, grafting can be carried out. The grafting time can be determined according to climate. When the temperature is below 20°C, the grafting survival rate decreases as the temperature drops. The best time of year for grafting is March to April, followed by August to October. If there is drought, irrigate 1-2 days before grafting to improve the grafting survival rate. High temperature and rainy weather, or low temperature and overcast rainy weather, are not suitable for grafting.
3. Grafting methods: Patch budding and cut grafting are mostly used.
(1) Patch budding method:
① Select rootstock with a diameter of 0.8 cm or more. At 30 cm above ground, open the bud grafting site by making two parallel cuts from top to bottom with a knife, 0.8 cm to 1.0 cm wide and 3 to 3.5 cm long. Cut the upper end of the incision into a tongue shape, then lift the bark and tear the cortex downward, removing most of the cortex while leaving a small section.
② Select 1 plump bud from the middle-upper part of the scion. With the bud as the center, cut a square piece around it 2.5 to 3.0 cm long and 0.5 to 0.7 cm wide, deep to the xylem. Then use the knife edge to insert flatly on the right side of the incision and push left; then insert on the left side and push right, and remove the bud piece. Alternatively, cut a bud piece 3 to 5 cm long and 1.2 to 1.5 cm wide with xylem, then trim the edges to a width of 0.5 to 0.7 cm, tear off the xylem, and cut to 2.5 to 3.0 cm.
③ Place the peeled bud in the center of the grafting site, insert the lower end into the pocket bark, leave a small gap at the upper end and both sides with the rootstock incision, press the bud piece tightly, and tie the bud piece with ultra-thin film 0.8 to 1.0 cm wide.
④ 20 to 30 days after grafting, once the grafting site has healed, cut off the upper part above the rootstock bud grafting site. Wait until the grafted bud swells and protrudes before removing the tie.
(2) Cut grafting method:
① Select rootstock with a diameter of 0.5 cm or more. At 30 cm above ground, cut the rootstock diagonally, then make a straight vertical cut downward on the higher side about 2 cm long, with depth suitable for removing part of the xylem, then cut away 1/2 or 2/3 of the cortex.
② Cut the base of a scion similar in thickness to the rootstock (containing 1 to 3 buds) into a slant, and make a smooth cut from top to bottom on one side of the tip, the same length as the rootstock, removing 2/3 of the cortex.
③ Insert the scion into the rootstock incision so that the cortexes match, tie tightly from bottom to top with ultra-thin film, and seal and wrap the scion well.
4. Management of grafted seedlings:
(1) Bud removal: After decapitation grafting, adventitious buds often sprout from the lower part of the rootstock below the grafting site. They must be checked once a week and removed promptly to avoid affecting the growth of the grafted bud. Of the buds sprouting from the scion, also keep only 1 and remove the rest.
(2) Re-grafting: 3 weeks after grafting, check whether the scion has survived. If not, re-graft promptly.
(3) Fertilizer and water management: The nursery should always remain moist, neither drought-stressed nor waterlogged. During drought, irrigate promptly. One month after grafting, apply dilute fertilizer water; apply urea solution once every other month. Apply fertilizer frequently and thinly, gradually increasing the fertilizer concentration month by month.
(4) Pest and disease control: During the seedling stage, pests and diseases are prone to occur, especially the fruit-piercing moth and anthracnose, so attention should be paid to their control.
(5) Shaping: After grafting, the sprouted main branch, once mature, should be topped at about 20 cm to promote side branch development. When side branches grow to 15-20 cm, pinch off the tips, and successively promote secondary side branches.
5. Timing and methods of lifting seedlings: Bagged seedlings can leave the nursery in all four seasons, but orchards with inconvenient irrigation should not plant in winter (November to February of the following year). When leaving the nursery, new shoots must be mature; if they are not mature and must leave the nursery, the new shoots should be cut off. At the same time, shorten or thin out excessive and overly long branches and leaves.
10 days before bagged seedlings leave the nursery, dig up the seedlings together with the whole bag, cut off roots outside the bag, place them in rows in the original location, and shade them, taking care to keep the seedling bags intact and the soil ball not loose.
6. Seedling selection: For commercial planting, grafted seedlings are always selected. The basic requirements for purchased or self-propagated grafted seedlings leaving the nursery are:
① Variety purity greater than or equal to 97%.
② The grafting site is no more than 30 cm above ground; the rootstock incision diameter is greater than or equal to 0.8 cm; the scion has produced more than 2 flushes of shoots, each flush having more than 3 complete mature leaves, the shoots produced by the scion are greater than or equal to 15 cm long, and the diameter at 5 cm from the incision is greater than or equal to 0.5 cm.
③ The incision has healed well, with no tumors or strangulation by tying bands.
④ Good growth vigor, sound and complete leaves, glossy, free of quarantine pests and diseases such as leaf blight and free of wilting. Stems and branches have no broken skin or cracks.
⑤ For bagged seedlings, the soil column diameter is greater than or equal to 11 cm, the height is greater than or equal to 21 cm, and the root system is complete; if large roots are broken due to movement, the seedlings may leave the nursery only after new roots grow and the leaves return to normal.
⑥ When leaving the nursery, watering of bagged seedlings should be stopped; when leaving the nursery, the soil column should be firm and the bag should not rot.
Before lifting seedlings, plant quarantine certificates should be processed in accordance with the national "Plant Quarantine Regulations", and seedlings with quarantine objects are strictly prohibited from being transferred into protected areas.
Bagged seedlings should keep the plastic bag and soil column intact, and tender shoots still in the growth period should be cut off. If the scion has produced more than three flushes of shoots, the upper more tender part may be cut off, keeping 2 to 3 mature flushes. During transport, take care to keep the seedling bags intact and the soil ball not loose. Strictly prevent heavy pressure, sun exposure, and rain during transport; transport by covered truck is preferable. After arriving at the destination, unload the seedlings immediately, place them under tree shade or in a shade shed, and plant them as early as possible (or heel them in temporarily).
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