Propagation of Pinus sylvestris var. mongolica grafted Pinus koraiensis seedlings

Pinus sylvestris var. mongolica has strong adaptability, cold resistance, drought resistance and barren resistance. Grafting Korean pine with Pinus sylvestris var. mongolica as rootstock has the advantages of early flowering and fruiting, quick garden formation and good effect.

1 preparation of scion

1.1 selection of Mother Tree

Choose excellent mother tree as scion. The tree height, DBH, crown width, fruiting layer thickness, young fruit number, cone number, male and female flowers of each clone were measured in the selected area. at the same time, seed collection per plant, cone number, cone weight, seed yield, seed emergence rate, kernel emergence rate, empty shell rate, insect damage rate, 1000-grain weight and cone length and width were tested. The single tree with high yield was selected as the mother tree.

1.2 Collection of scions

The scion should be collected in the first and middle March of the grafting year, and the collection site should be on the outer 1-year-old branches in the middle and upper part of the trunk of the mother tree. The middle and lower parts and inner bore branches grow weakly and are not suitable for scion. Strip harvesting should protect the growth of excellent mother trees from being affected, and should not be picked too much at one time. According to the size of the mother tree, there are generally 10-50 branches per tree, each branch with the vegetative branch of 15~20cm, and then bundled according to the number of the superior tree.

1.3 Storage of scion

The storage of scion will directly affect the survival rate of grafting. If the harvesting place is far from the storage place and requires long-distance transportation, the branches should be packed in plastic bags, sealed with a small amount of sawdust and moisturized. It is better to store branches in an ice cellar, and the size of the cellar depends on the number of scions. Before entering the cellar, put snow or ice cubes about 50cm thick at the bottom of the scion, and finally cover the scion with snow or ice, and then seal the pit.

2 selection of rootstocks

The grafting rootstock Pinus sylvestris var. mongolica is suitable for transplanting large seedlings with high 40~50cm. In the first 1 ~ 2 years of grafting, 2-3-year-old seedlings with strong growth and free of diseases and insect pests were selected to change beds in the nursery or planted on woodland. Changing the bed in the nursery can be done with 2-year-old seedlings after changing beds for 1 year, and 3-year-old seedlings can be planted in the afforestation site.

3 grafting supplies

3.1 plastic strips

PVC agricultural plastics with strong telescopic ability were selected and cut to grow strips with a width of 35 × 1cm. It is used to bind the marriage interface.

3.2 adhesive strips

Medical white glue strips. Used for hanging labels and so on.

3.3 Alcohol, skimmed cotton

Used for wiping blades, etc.

3.4 Blade and tool holder

Double-sided or single-sided surgical blade (No. 22), single-sided blade is better. It is used to cut the grafting section.

3.5 pruning shears

Used for pruning scions and rootstocks.

4 grafting period and method

The grafting period can be divided into spring and summer, preferably when the sap flows in spring (about mid-April).

The grafting site can be divided into the top of the central leading branch and the upper end of the first to third whorl branches. The survival rate of grafting is low due to the thick bark of the central leading branch and the poor matching between scion and rootstock, so it should be grafted at the site of 1-3 whorls of branches.

Among the grafting methods, the survival rate of pith cambium grafting was the highest. The suitable thickness of scion is about 2 to 3 of the thickness of the grafting site of rootstock. The scion was cut from the upper 7~8cm of the 1-year-old branch, and 8-10 needles were retained at the top. The rest of the needles were pulled out along the needle direction and cut at the left and right of the lower 0.5cm of the reserved needles. the cutting surface was 6~7cm and the depth reached the pith. The one-year-old main branch of the rootstock is the suitable part for grafting. After pulling out the needles in the grafting part, cut the section equal to the length of the scion and reach the depth to the forming layer. After combining the scion with the rootstock, tie it tightly with a plastic strip. It is required that the section should be smooth, preferably completed with a knife, the section of the scion should not be larger than the section length of the rootstock, and the grafting operation should be fast in order to reduce the flow of glue.

5 Management after grafting

At the beginning of May, the terminal buds of scions begin to sprout gradually. The terminal buds and lateral buds of grafted rootstocks should be cut off, and then the wound should be smeared with lead oil. The banding was untied for the first time from the end of May to the beginning of June, and the dead plant was untied completely. The second loosening was carried out in mid-late July, and the top and lateral buds of all whorled branches exceeding the grafting height were cut off at the same time. After the current year's branches of Pinus sylvestris var. mongolica were cut, many adventitious buds grew and formed many young branches, which should be cut again in autumn, but the vegetative branches should not be cut off once, so as to affect the grafting overwintering and survival.

Remove the bound plastic strip about 90 days after grafting or before the spring grafting bud germinated in the following year, and cut off the terminal buds of the main branches and some side branches of the rootstock. The tree potential management should be carried out continuously for 5-7 years after the grafting survived. Because the height growth of the scion was less than that of the rootstock within a few years after the grafting survived, the main branch position of the scion was easily replaced by the lateral branches. In order to keep the scion in the position of the main branch, the top of the lateral branches affecting the growth of the scion should be pruned once a year in early spring, and pruning to promote fruiting should be carried out after 8-10 years.