Low-cost large-scale breeding method for dwarf self-rooted seedlings of pear tree middle dwarf No.1

Abstract

According to the low-cost large-scale breeding method for the dwarf self-rooted seedlings of the pear trees in the middle-dwarf No.1 mode, a multi-year-old seed tree which takes pyrus betulaefolia as a base stock and is grafted with the middle-dwarf No.1 is planted in a small arched shed of a field, and early-stage management is carried out to ensure healthy growth of the seed tree. Then, within a specific time range, the illumination and temperature are regulated and controlled by covering plastic cloth and a sunshade net, girdling treatment is conducted on the selected branches, then rooting hormone is sprayed, and a heat-preservation and moisture-preservation high-oxygen-content substrate beneficial to rooting is covered. Meanwhile, the drip irrigation system is used for accurately controlling water supply, and the optimal temperature and humidity conditions are maintained to promote rooting. By means of the measures, the purpose of completing the process from planting the seed tree to successfully breeding the dwarf self-rooted seedlings of the middle-dwarf No.1 in the same year is achieved. The method can significantly improve the breeding efficiency and the seedling quality, and promotes the modern development of pear tree cultivation.

Description

Technical Field

[0001] The present invention belongs to the technical field of fruit propagation, and particularly relates to a method for large-scale propagation of self-rooted dwarfing seedlings of Zhong'ai No. 1 pear trees at low cost. Background Art

[0002] As the third largest cultivated fruit tree in China, pear trees rank first in terms of cultivated area, yield, and export volume globally. The cultivation of dwarf and high-density pear trees is the development trend of modern pear cultivation, which is conducive to achieving early fruiting, high yield, high quality, and high efficiency. Among them, the cultivation of self-rooted dwarfing seedlings is regarded as an important prerequisite and basic condition for modern pear cultivation.

[0003] Pear tree cultivation rootstocks are divided into seedling rootstocks (including dwarf interstocks) and self-rooted dwarfing seedlings. Seedling rootstocks (including dwarf interstocks) are rootstock seedlings obtained by sowing seeds, such as Pyrus betulaefolia and Pyrus calleryana. Dwarf interstocks are obtained by grafting dwarf rootstocks after sowing. The seeds sown for seedling rootstocks are obtained through pollination and belong to sexually hybridized seeds. According to plant genetics theory, the seeds obtained in this way have serious trait segregation (trait segregation caused by gene recombination, with a variation rate of 30%-45% among individual plants). The rootstocks obtained after sowing show the following characteristics when used for cultivation: the biological characteristics of each tree in an orchard are different, the crown sizes are uneven, management is difficult and time-consuming. It starts to bear fruit 5-6 years after planting, has a late onset of the high-yield period, serious biennial bearing phenomenon, low yield, high management cost, inconsistent fruit quality, and low commerciality. In addition, due to the large crown, to ensure yield and quality, more chemical fertilizers and pesticides are applied, resulting in high costs and serious pollution, and low economic benefits. Therefore, the cultivation of seedling rootstocks does not meet the development trend of modern pear cultivation.

[0004] Self-rooted dwarfing seedlings are obtained by asexual propagation using excellent dwarf rootstocks. Since they are obtained by asexual propagation methods during the propagation process, this method can maintain all the excellent traits of the mother plant, with a very low mutation rate, which is suitable for achieving the goals of early fruiting, high quality, and high efficiency, and is conducive to standardized management and precise management of fertilizer, water, diseases, and pests, improving the consistency and stability of fruit quality. It is precisely because of the many advantages of the cultivation of self-rooted dwarfing pear trees that the cultivation of self-rooted dwarfing pear trees has become the preferred method and trend in the development of world pear cultivation.

[0005] According to different genetic backgrounds, the rootstocks for pear tree cultivation in the world are mainly divided into two categories: occidental pear rootstocks and oriental pear rootstocks. Although some western pear rootstocks have been introduced into China for experiments, they have not been widely used due to problems such as poor compatibility, poor anchorage, yellowing of leaves in alkaline soil, and poor cold resistance and rot resistance. Since the 1970s, China has made progress in the breeding of dwarfing rootstocks for pear trees, and has successfully cultivated three series: Zhong'ai series, K series and D series. In particular, Zhong'ai No. 1 shows wide adaptability and good dwarfing effect. However, due to reproductive technology limitations (there is no successful case of the technology for propagating self-rooted seedlings of Zhong'ai No. 1 by asexual propagation methods such as tissue culture, layering, and cutting commonly used at present), it is currently mainly used as a seedling intermediate rootstock, which affects the full play of its performance and also affects the development of modern pear trees in China.

[0006] In order to promote the modernization of pear tree cultivation, it is urgent to solve the technical problem of low-cost industrialized propagation of self-rooted seedlings of Zhong'ai No. 1, so as to make full use of the advantages of the dwarfing rootstock of Zhong'ai No. 1, and promote the healthy development of the pear tree industry and the improvement of economic benefits. Summary of the Invention

[0007] (I) Technical Problems to be Solved

[0008] In view of the above-mentioned disadvantages and deficiencies in the prior art, the present invention aims to provide a low-cost and large-scale propagation method for self-rooted dwarf seedlings of Zhong'ai No. 1 pear trees, so as to realize the industrialized production of self-rooted dwarf seedlings of Zhong'ai No. 1, overcome the limitations of traditional propagation technologies, ensure the stable inheritance and efficient expression of excellent variety characteristics, which is of great significance for improving the overall level and economic benefits of the pear tree cultivation industry, and helps to achieve the goal of high-quality and efficient agricultural development.

[0009] (II) Technical Solutions

[0010] The present invention provides a low-cost large-scale propagation method for self-rooted dwarf seedlings of Zhong'ai No. 1 pear trees, including the following steps:

[0011] S1. Selection and Planting of Mother Trees

[0012] The mother tree is selected as a two-year-old or older Pyrus betulaefolia Bunge rootstock grafted with Zhong'ai No. 1 with a basal diameter of 1.5 - 3 cm; the mother tree is planted after the local soil thaws, and the planting depth is such that the Zhong'ai No. 1 section is buried below the surface soil; before planting the mother tree, a small arched shed area with a north-south orientation is planned in the breeding nursery, and a small arched shed skeleton without film cloth is built in the small arched shed area, and the mother tree is planted in the planned small arched shed area;

[0013] S2. Cutting the Rootstock and Promoting Shoots

[0014] After planting the mother tree, water it to ensure the survival of the mother tree. After the first watering, cut the rootstock, and cut off the Zhong'ai No. 1 rootstock at a position 3 - 4 cm above the ground surface to promote the growth of new shoots;

[0015] S3. Set up a small arched shed

[0016] Cover the top of the small arched shed with a film cloth and a sunshade net with a light transmittance of 50 - 60%, leave ventilation openings at both the north and south ends, and seal the rest; the mother trees grow in the small arched shed from germination until the new shoots take root.

[0017] S4. Management of new shoots

[0018] Use a drip irrigation system to keep the soil moisture content at 35 - 38%, apply water-soluble fertilizer to the mother trees through the drip irrigation system, thin out the thin, weak, medium-short and No. 1 new shoots, and leave 2 - 3 strong-growing new shoots; during this period, conduct pest and disease control, remove weeds and Pyrus betulifolia buds in a timely manner.

[0019] S5. Girdling and hormone treatment of new shoots

[0020] Conduct girdling during the critical period when the new shoot cells differentiate to form adventitious root primordium cells; remove the film cloth, sunshade net and drip irrigation system 1 - 3 hours (not in advance) before girdling, make a circumferential cut around the new shoot at a distance of 3 - 5 cm from the ground surface and remove the epidermis of the girdled new shoot, the girdling depth reaches the cambium layer without damaging the cambium layer, and immediately spray a rooting hormone circumferentially within the range of 1 - 2 cm above and below the girdling opening after girdling.

[0021] S6. Landfill the substrate

[0022] After the hormone spraying is completed, landfill the substrate in the small arched shed area and make the substrate fully contact with the girdling opening of the new shoot, spray water to make the substrate compact and keep the substrate thickness at 9 - 11 cm; the substrate is obtained by crushing the mushroom stick materials after mushroom harvesting into powder particles and then mixing them wet with urea and carbendazim solution.

[0023] S7. Root-promoting management of new shoots

[0024] Restore the film cloth, sunshade net and drip irrigation system of the small arched shed to their original state, leave ventilation openings at both the north and south ends; control the temperature and humidity of the substrate at the girdling opening at 31 - 31.5°C and 45 - 48% on the 1st - 7th day after landfilling the substrate; starting from the 8th day, control the temperature and humidity of the substrate at the girdling opening at 23 - 25°C and 34 - 36%; four months later (after mid-September), ventilate day and night around the small arched shed, and completely remove the small arched shed when the new shoot leaves turn to the normal color of open-field leaves and the epidermis turns brown.

[0025] S8. Dig out the seedlings and temporary planting

[0026] Before the autumn and winter leaves fall and before the soil freezes, dig out the substrate, cut at the girdling opening to obtain self-rooted seedlings, and temporarily plant the self-rooted seedlings indoors for the winter.

[0027] According to a preferred embodiment of the present invention, in S1, before planting the mother tree, the root system of the mother tree is pruned and sorted out, including: removing the diseased roots and damaged roots of the mother tree, shortening the overlong vertical roots and horizontal root systems of the mother tree, so that the vertical roots are reserved at 20 cm ± 2, and the horizontal root systems are reserved at 12 - 16 cm.

[0028] According to a preferred embodiment of the present invention, in S1, after pruning and sorting out the root system of the mother tree, the pruned root system of the mother tree is soaked in a 1# rooting powder solution of 3000 ppm for 8 - 12 min, and then taken out for planting; the planting time of the mother tree is in mid-March, and the planting depth is such that the middle-short 1 segment is buried 5 - 8 cm below the surface soil, that is, 5 - 8 cm of the main trunk of the middle-short 1 is in the soil. According to a preferred embodiment of the present invention, S0 is also included before S1: planning a small arch shed area in the breeding nursery, the small arch shed is arranged in the north-south direction, the single shed is 9 - 11 meters long and 1.4 - 1.6 meters wide; a 0.5 - 0.55 m space is left between each small arch shed as an operation path; when planting the mother tree, the mother tree is planted in the planned small arch shed area, and the planting is carried out with a north-south plant spacing of 20 cm ± 1 and an east-west row spacing of 34 - 36 cm.

[0029] According to a preferred embodiment of the present invention, in S2, water is promptly applied after planting the mother tree, and the tilted mother tree is righted after the first watering, and then watering is carried out every 7 days; after the first watering, the rootstock is cut, and the middle-short 1 rootstock is cut off at a position 3 - 4 cm above the ground surface to promote the growth of new shoots.

[0030] According to a preferred embodiment of the present invention, in S1, when building the small arch shed framework, a number of small arch rings are arranged at intervals in the north-south direction, and the small arch rings are firmly connected by connecting rods, and the top height of the small arch shed is set at 1 - 1.2 m; in S3, a non-drip film cloth is covered on the small arch shed, and a sunshade net with a light transmittance of 50 - 60% is covered on the non-drip film cloth; except for leaving ventilation openings at both the north and south ends, the other parts are compacted with soil for the non-drip film cloth and the sunshade net.

[0031] According to a preferred embodiment of the present invention, in S3, a single small arch ring is made of a 1-inch steel pipe and bent according to the standard by a pipe bending machine, the adjacent small arch rings are spaced 1 m apart, and the small arch rings are connected and tied firmly with 1-inch steel pipes.

[0032] According to a preferred embodiment of the present invention, in S4, the drip irrigation system adopts a two-stage pipeline. The first-stage pipeline is a number of 2-inch EP plastic pipelines arranged in the east-west direction. One end of the first-stage pipeline is connected to a water-soluble fertilizer fertilization device or a well water source, and the other end is blocked; the second-stage pipeline is a drip irrigation capillary tube arranged in the north-south direction beside the mother tree in the small arch shed area. Four rows of drip irrigation capillary tubes are arranged in each small arch shed area. One end of the second-stage pipeline is connected to the first-stage pipeline through a valve, and the other end is blocked; holes are drilled in the drip irrigation capillary tube and drip heads are installed, and the drip heads are located beside each mother tree.

[0033] According to a preferred embodiment of the present invention, in S4, a drip irrigation system is adopted to maintain the soil water content at 35-38%. When the soil water content is low, the deep well pump is turned on to supply water. By adjusting the valve between the secondary pipeline and the primary pipeline, the drip heads in each small arch shed area can drip water evenly. During fertilization, water-soluble fertilizer is applied to the mother trees through the drip irrigation system. The water-soluble fertilizer is a balanced fertilizer with a nitrogen:phosphorus:potassium ratio of 10:10:10.

[0034] According to a preferred embodiment of the present invention, in S4, the removal of Pyrus betulifolia Bunge buds includes removing them when they just emerge from the ground surface, thereby reducing the nutrient loss of the mother trees and enabling the new shoots of Zhong'ai No. 1 to grow robustly. When the new shoots grow to 4-5 cm, operations such as girdling and root promotion are started to be prepared.

[0035] According to a preferred embodiment of the present invention, in S5, the girdling time is carried out during the critical period of cell differentiation to form adventitious root primordium cells until the end of the critical period of adventitious root primordium cell differentiation. The judgment method of the critical period is as follows: when the basal diameter of the current-year new shoots of Zhong'ai No. 1 reaches 0.3-0.5 cm, the basal epidermis is light green, the lenticels are not obvious, the xylem color is greenish-white, the pith color is greenish-white, and the leaf color is light green without being mature and aging, it indicates the start of the critical period of adventitious root primordium cell differentiation (the best girdling time); when the new shoot leaves are mature and aging, the new shoot epidermis begins to turn brown, the lenticels appear, the xylem color is white, and the pith color is white, it indicates the end of the critical period of adventitious root primordium cell differentiation, and at this time, the girdling should be stopped immediately.

[0036] According to a preferred embodiment of the present invention, in S5, the girdling time starts in the middle and late May. If it is too early, the new shoots do not meet the requirements; if it is too late, the rooting rate is very low. The girdling width is preferably 0.05-0.1 cm. Immediately after girdling, a rooting hormone is sprayed. The composition of the rooting hormone is 1200 ppm of rooting powder No. 1 + 0.4-0.45 ppm of indolebutyric acid. It is evenly sprayed circumferentially in the range of 1-2 cm above and below the girdling mouth, and the spraying time of the hormone for each new shoot is 1-1.5 s. Among them, when girdling, because the new shoots are thin, brittle and tender, the operation should be careful and delicate to prevent breaking the new shoots. Destroying the cambium and having too wide a girdling width will cause the new shoots to die due to the non-healing of the callus above and below the girdling mouth before adventitious roots grow, affecting rooting.

[0037] According to a preferred embodiment of the present invention, in S6, the substrate is prepared by crushing the mushroom stick material after mushroom harvesting into powder particles the size of sawdust, and then uniformly wetting it with a solution containing 3‰ urea + 800 times carbendazim, adjusting the water content to 35 - 40% for standby; after the hormone spraying is completed, the substrate is landfilled in the small arch shed area and the substrate is fully contacted with the girdling mouth of the new shoot. The initial landfilling thickness is 10 - 12 cm above the ground (if the substrate is too thin or too thick, it is not conducive to meeting the temperature and humidity required for rooting). After the substrate landfilling is completed, artificial spraying is used to make the substrate compact and in close contact with the girdling mouth of the new shoot without gaps. After spraying, the final thickness of the substrate is maintained at 9 - 11 cm. If the substrate is too thin or too thick, it is not conducive to regulating the temperature and humidity required for new shoot rooting.

[0038] According to a preferred embodiment of the present invention, in S7, the requirements for air temperature and humidity in the small arch shed are as follows: from 8 am to 7 pm on the 1st - 7th days, the temperature is 31 - 32 °C, from 8 pm to 8 am the next day, the temperature is 30 - 30.5 °C, and the humidity throughout the day is 55 - 60%; the requirements for temperature and humidity of the substrate at the girdling mouth on the 1st - 7th days are: the temperature is 31 - 31.5 °C, and the humidity is 45 - 48%;

[0039] Starting from the 8th day, the requirements for air temperature and humidity in the small arch shed are: the temperature is 26.5 - 28.5 °C, and the humidity is 35 - 40%; the requirements for temperature and humidity of the substrate at the girdling mouth are: the temperature is 23 - 25 °C, and the humidity is 34 - 36%; starting from the 22nd day, the requirements for temperature and humidity of the substrate at the girdling mouth are: the temperature is 23 - 25 °C, and the humidity is 32 - 34%;

[0040] After 4 months (around mid - September), ventilation starts day and night around the small arch shed. When the leaves of the new shoot turn to the normal color of open - field leaves and the epidermis turns brown, the plastic film and sunshade net are completely removed.

[0041] According to a preferred embodiment of the present invention, in S7, the drip irrigation capillary is restored to its original position, so that a drip head is set beside each mother tree, and the film cloth and sunshade net of the small arch shed are restored to their original state; the film cloth is pressed firmly with soil in the east - west direction, and ventilation openings and observation openings are left at both the north and south ends; an air temperature and humidity monitor and a soil temperature and humidity monitor are set in the small arch shed; the probe of the air temperature and humidity monitor monitors the temperature and humidity at the top of the new shoot, and the probe of the soil temperature and humidity monitor monitors the temperature and humidity at the girdling mouth of the new shoot inside the substrate; the monitoring data of the air temperature and humidity monitor and the soil temperature and humidity monitor are displayed outside the small arch shed; the set temperature and humidity requirements are achieved by regulating the dripping speed of the drip head and the size of the ventilation openings at both the north and south ends.

[0042] According to a preferred embodiment of the present invention, in S7, during the entire management period of promoting root growth of the new shoot, a pest and disease control liquid medicine is sprayed on the mother tree once every 26 days. The composition of the pest and disease control liquid medicine is: a diluted solution of 800 times carbendazim + 600 times thiophanate - methyl + 2000 times imidacloprid.

[0043] According to a preferred embodiment of the present invention, S8 includes: after lifting the self-rooted seedlings, grading them, dividing them into large, medium, and small grades according to national standards, and performing temporary planting respectively; then performing indoor temporary planting, with the temporary planting substrate being river sand and the humidity of the river sand being 35 - 45%; in the temporary planting pit, through the alternating layer laying method of river sand - seedling - river sand, the self-rooted seedlings are temporarily planted one by one. The self-rooted seedlings can be officially transplanted into the field in the following year. During the temporary planting process, it is ensured that the river sand fills the gaps between the roots of the self-rooted seedlings, and the roots are in full contact with the sand. The temporary planting method can be: first, place a layer of sand with a width of 50 cm and a thickness of 20 cm in the temporary planting pit, then place a single layer of self-rooted seedlings, then fill in another layer of sand, and then place a single layer of self-rooted seedlings again, and so on in alternation.

[0044] According to a preferred embodiment of the present invention, S8 further includes: after lifting the seedlings, leveling and insulating the substrate in each small arch shed and watering it to ensure the safe wintering of the mother trees. These mother trees can continue to reproduce a large number of self-rooted seedlings according to the steps S2 - S8 of the present invention in the following year, greatly reducing the cost of self-rooted seedling reproduction in the coming year.

[0045] According to a preferred embodiment of the present invention, when there are multiple small arch sheds arranged in a breeding nursery, operations such as new shoot girdling, hormone treatment, landfill of substrate, restoration of the film, sunshade net, and drip irrigation system in one small arch shed need to be continuously carried out and completed before starting the operations in the next small arch shed; that is, when operating on one small arch shed, the remaining small arch sheds remain covered with the film; each small arch shed sequentially completes the following operations: new shoot girdling, spraying rooting hormone, landfill of substrate, installation of drip irrigation capillary, restoration of the film and sunshade net, and reinforcement of the film around the small arch shed. Thus, all the operations of one small arch shed are completed; then the same operations are carried out on the next small arch shed. It is not allowed to remove the film, sunshade net, and drip irrigation system of all the small arch sheds in the breeding nursery at one time to prevent the new shoots from lignifying rapidly after being exposed to the open air due to untimely operations. The small arch shed and the sunshade net play a key role in the present invention. They are set for the slow growth and early cessation of growth of Zhong'ai No. 1 under open-air conditions, and can provide feasible conditions for promoting root growth of self-rooted seedlings.

[0046] (III) Beneficial effects

[0047] The present invention provides a method for efficiently breeding self-rooted dwarfing seedlings of Zhongai No. 1 pear trees in small arch sheds in the field. By planting perennial mother trees grafted with Zhongai No. 1 on Pyrus betulifolia Bunge as the basic rootstock in the small arch sheds in the field and carrying out preliminary management to ensure their healthy growth. Subsequently, within a specific time range, by covering with plastic sheets and sunshade nets to regulate light and temperature, girdling selected branches and then spraying rooting hormones, and covering with a specific substrate conducive to rooting. At the same time, using a drip irrigation system to precisely control water supply and maintaining the best temperature and humidity conditions to promote rooting. Through the above measures, the goal of completing the breeding of self-rooted dwarfing seedlings of Zhongai No. 1 from planting mother trees to successful breeding is achieved within the same year. This method can significantly improve the propagation efficiency and seedling quality, and promote the modernization development of pear tree cultivation.

[0048] The present invention delays the aging of new shoots through the environmental regulation of small arch sheds, and combines with the mushroom stick substrate to provide an environment with high oxygen content, significantly improving the rooting rate; by precisely controlling the girdling width, hormone concentration, and temperature and humidity thresholds during the root-promoting management, ensuring repeatability and the rooting rate and rooting quality of new shoots, greatly increasing the harvesting rate of self-rooted seedlings. After lifting the seedlings, level and heat preservation the substrate in each small arch shed and water it to ensure the mother trees can survive the winter safely, and these mother trees can continue to reproduce a large number of self-rooted seedlings in the following year. The refined self-rooted seedling propagation technology of Zhongai No. 1 of the present invention has been experimentally proven to be feasible, realizing the low-cost industrialized breeding of self-rooted seedlings of Zhongai No. 1, making full use of the advantages of Zhongai No. 1 dwarfing rootstock, and promoting the healthy development of the pear tree industry and the improvement of economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a flowchart of the method for breeding self-rooted dwarfing seedlings of Zhongai No. 1 pear trees according to the present invention.

[0050] Figure 2 It is a schematic diagram of setting up small arch sheds and drip irrigation systems in the breeding nursery. DETAILED DESCRIPTION OF THE INVENTION

[0051] In order to better explain the present invention for easy understanding, the present invention will be described in detail below through specific embodiments.

[0052] Example 1

[0053] The process of the large-scale breeding method of self-rooted dwarfing seedlings of Zhongai No. 1 pear trees in this example is as follows:

[0054] (1) Plan the small arch shed area in the breeding nursery and build the small arch shed framework in the small arch shed area

[0055] The breeding nursery used for planting mother trees and breeding self-rooted seedlings of Zhongai No. 1 is called the breeding nursery. Before planting the mother trees, the breeding nursery and the small arch sheds in the nursery should be planned and sorted out first.

[0056] (1) Plan the small arch shed area in the breeding nursery

[0057] To better facilitate daylighting, several rectangular blocks with a north-south length are demarcated in the breeding nursery as the small arch shed area. For ventilation and light transmission and to reduce pests and diseases, the small arch sheds should not be too long. In a preferred embodiment, a north-south length of 10 meters is appropriate. To facilitate subsequent operations during the rooting process (including girdling, root promotion, etc.), the small arch sheds should not be too wide, and a width of 1.5 meters is appropriate. For convenient management, a 0.5-meter space is reserved between each small arch shed as an operation path. After planning the small arch shed area, the mother trees can be planted in an orderly manner according to the demarcated small arch shed area.

[0058] (2) Construct the small arch shed framework in the small arch shed area

[0059] Construct the small arch shed framework on the small arch shed area planned in the breeding nursery. The small shed plays an important role in the present invention. Its purpose is to delay the maturation and aging of the shoot pith, xylem, and phloem tissue organs while promoting the rapid growth of the current-year dwarfing rootstock shoots to reach the rooting thickness, maintaining their activity for better rooting, improving the shoot rooting rate and rooting quality, and thus obtaining a large number of qualified self-rooted seedlings in the current year. Since Zhongai No. 1 grows slowly and stops growing early, under open-air growth conditions, when the current-year shoots reach the required rooting thickness, the aging of the shoot tissue organs is already very serious. The more aged or mature the tissue organs are, the less conducive they are to shoot rooting. This is the main reason why there is currently no successful case of breeding Zhongai No. 1 self-rooted seedlings (the small annual growth of Zhongai No. 1 shoots is also one of the reasons). The length and width of each small arch shed are based on a length of 10 m and a width of 1.5 m for each small arch shed area. The arch height is based on 1 m from the ground surface to the top of the arch. Each single small arch ring is made of one-inch steel pipe and bent according to the standard by a pipe bending machine, and the distance between adjacent small arch rings is 0.9 - 1.1 m. The small arch rings are connected with one-inch steel pipes and tied firmly.

[0060] (II) Mother tree management

[0061] (1) Mother tree selection: The original tree species used for propagating Zhongai No. 1 dwarfing self-rootstock is called the mother tree. Due to the biological characteristics of Zhongai No. 1 itself, the annual growth of Zhongai No. 1 shoots is very small. Through summarization, under the same conditions, compared with other tall mother trees, the rooted shoots of weak mother trees are very few after treatment, which is related to the fact that weak trees produce less rooting hormone by themselves. Strong mother trees will produce more hormones conducive to the formation of adventitious roots. In the present invention, in order to achieve the goal of planting and breeding self-rooted seedlings in the current year, seedlings with a base stock of Pyrus betulifolia and grafted with Zhongai No. 1 at its base for more than two years (≥2 years) should be selected as the mother trees, and the mother trees need to be robust and have excellent growth, and the base diameter of the mother trees should reach 1.5 - 3 cm. At this time, the survival rate of the mother trees and the rooting rate of the shoots can be effectively guaranteed.

[0062] (2) Root treatment before planting the mother tree: Prune and trim the overly long vertical roots, horizontal roots, diseased roots, and damaged roots of the mother tree. Retain about 20 cm of vertical roots and about 15 cm of horizontal roots, ensuring that the mother tree has no diseased roots or damaged roots. This is more conducive to the healing and growth of root wounds, avoiding the death of the mother tree due to diseases, preventing infected damaged roots from spreading soil-borne pathogens, and facilitating the survival rate of the mother tree. To ensure the survival of the planted mother tree, then soak the pruned roots in a 3000 ppm No. 1 rooting powder solution for 10 minutes and take them out for planting.

[0063] (3) Planting the mother tree: The earlier the planting time after the local soil thaws, the better. Generally, it is advisable to start around mid-March (around March 20). Plant the mother tree in the planned small arch shed area. The north-south plant spacing is 20 cm, and the east-west row spacing is 35 cm. Plant four rows in each small arch shed area. The planting depth should be such that the Zhong'ai No. 1 section is buried 5 - 7 cm below the surface soil. This can reduce the sprouting of basal stock Pyrus betulifolia Bunge, facilitating the growth of new shoots of Zhong'ai No. 1.

[0064] Water the mother tree in time after planting. Straighten the tilted mother tree after the first watering. Then water once every 7 days for a total of three times, and observe the growth trend of the mother tree in real time to ensure the survival of the mother tree.

[0065] (4) Cutting the rootstock of the mother tree: Cut the rootstock after the first watering. The method is as follows: After straightening the tilted mother tree after the first watering, start cutting the rootstock. Cut the Zhong'ai No. 1 rootstock at a position 3 - 4 cm above the ground surface to promote the sprouting of new shoots.

[0066] (5) Setting up the drip irrigation system and covering with a non-drip plastic film and sunshade net

[0067] The mother tree grows in the small arch shed from germination to before the new shoots take root. Therefore, precise water management is very important. The leaves and other organs of the new shoots of Zhong'ai No. 1 are relatively tender and have low disease resistance. The small arch shed has good moisture retention performance. However, high humidity will increase the diseases of the new shoot leaves and various organs, reducing the rooting rate of the new shoots. To ensure the humidity of the substrate required for rooting while reducing the occurrence of diseases, the present invention uses a drip irrigation system to precisely control the humidity of the soil and the subsequent root-promoting substrate. Compared with other micro-spray pipes, artificial sprinkler irrigation, etc., the drip irrigation system can better avoid the direct contact of the leaves and other organs above the ground surface with the water during the water replenishment and humidity increase process on the premise of ensuring the humidity of the substrate required for rooting. The non-drip film of the small arch shed can prevent humidity from gathering at the top of the small arch shed and forming water droplets that directly contact the leaves and other organs, reducing the humidity of the new shoot leaves and various organs and the probability of disease occurrence, which is conducive to improving the rooting rate of the new shoots.

[0068] ① Install a drip irrigation system in the small arch shed

[0069] The drip irrigation system used for drip irrigation adopts a two - level pipeline method. The first - level pipeline consists of several 2 - inch EP plastic pipelines arranged in the east - west direction (the number of the first - level pipelines is the same as the number of rows of small arched greenhouses arranged in the north - south direction in the breeding nursery, and the length is the same as the east - west length of the breeding nursery). One end of the first - level pipeline is connected to the water - soluble fertilizer application equipment or the well water source, and the other end is blocked. The second - level pipeline is the drip irrigation capillary tube arranged in the north - south direction beside the mother trees in the small arched greenhouse area. The length of each second - level pipeline is the same as the north - south length of the small arched greenhouse. Four rows of drip irrigation capillary tubes are set in each small arched greenhouse area, and holes are drilled and drip heads are installed at the corresponding positions of the drip irrigation capillary tube and the mother trees. The drip heads are located beside each mother tree. One end of the second - level pipeline is connected to the first - level pipeline through a valve, and the other end is blocked. The setting method is shown in Figure 2 。 Figure 2 In Figure 2 , 1 is the breeding nursery, 2 is the small arched greenhouse, 3 is the first - level pipeline, 4 is the second - level pipeline (drip irrigation capillary tube), 5 is the mother tree, and 6 is the valve.

[0070] ②Cover with non - drip plastic film and sunshade net

[0071] Cover the small arched greenhouse frame with plastic non - drip film, leaving the north and south ends uncovered tightly for easy observation and ventilation, and pressing the plastic film and sunshade net tightly with soil at the east and west ends.

[0072] Cover the plastic cloth with a sunshade net with a light transmittance of 50 - 60%. The sunshade net can block most of the sunlight. Its purpose is also to extend the aging time of the new shoots, which is more conducive to leaving time for root - promoting operations and the rooting rate of new shoots. Except for leaving ventilation openings at the north and south ends of the small arched greenhouse, the other parts are compacted with soil for the plastic cloth and sunshade net.

[0073] (6) Pest control of mother trees

[0074] After the mother trees germinate, pest control should be carried out in a timely manner to ensure the healthy growth of the new shoots of the mother trees. Since the mother trees grow in the greenhouse and have poor drug resistance, the dosage of pesticides should be lower than that in the open air to avoid causing phytotoxicity. From the germination of new buds to the start of girdling, imidacloprid at a concentration of 2000 times is sprayed once every 20 days to control pests.

[0075] (7) Water and fertilizer management

[0076] Strengthen the water and fertilizer management of mother trees to promote the growth of new shoots. During the period when the mother trees germinate new shoots, ensure that the soil moisture content is between 35 - 38%. Use a soil temperature and humidity detector to measure the soil moisture content. When it is monitored that the soil moisture content is low, turn on the deep - well water pump to supply water. By adjusting the opening and closing degree of the valve between the second - level pipeline (drip irrigation capillary tube) and the first - level pipeline, ensure that each drip head of the drip irrigation capillary tube in each small arched greenhouse area can drip water evenly. Water each small arched greenhouse area one by one to ensure that each drip head drips water evenly. The fertilizer uses water - soluble fertilizer and is applied to the mother trees through dripping. The water - soluble fertilizer uses a balanced fertilizer with a nitrogen: phosphorus: potassium ratio of 10:10:10.

[0077] (8) Weeding: Remove weeds in a timely manner before the new shoots of the mother tree take root to avoid affecting the growth of the new shoots of the mother tree.

[0078] (9) Sprouting removal: When using Pyrus betulifolia as the rootstock and grafting Zhongai No. 1 as the mother tree, the buds of Pyrus betulifolia will germinate. The germinated buds of Pyrus betulifolia must be removed when they first emerge above the ground surface, which can reduce the nutrient loss of the mother tree and make the new shoots of the mother tree grow more robustly.

[0079] (10) Thinning out weak Zhongai No. 1 new shoots

[0080] Remove the weak Zhongai No. 1 new shoots on the mother tree with small growth amounts, and leave 2 - 3 robust new shoots. After cutting the rootstock of the mother tree, the mother tree generally sends out more than 3 Zhongai No. 1 new shoots. The growth amount of the current-year Zhongai No. 1 new shoots is relatively small. Thinning out weak branches can ensure that the current-year new shoots can meet the requirements for rooting, so as to concentrate nutrients and ensure that the remaining new shoots grow to meet the rooting requirements. When the new shoots grow to 9 - 12 new leaves, start preparing for new shoot rooting. (III) Substrate preparation

[0081] The substrate uses the materials inside the mushroom sticks after mushroom harvesting. Most mushroom substrates use a mixture of sawdust powder, rice husks, and cottonseed hulls. Compared with substrates such as sand or soil, these substances have the characteristics of high water content, high temperature, high oxygen content, and relatively stable temperature and humidity. This characteristic very much meets the conditions of high temperature, high humidity, and high oxygen content necessary for new shoot rooting. Method for preparing the substrate: Crush the mushroom stick materials after mushroom harvesting to the size of sawdust powder particles, and then evenly moisten them with a solution containing 3‰ urea + 800 - fold carbendazim, and adjust the water content to 35 - 40%, then it can be used. Other common nursery substrates are difficult to meet the root-promoting requirements of Zhongai No. 1 new shoots in terms of their own specific gravity, heat preservation and moisture retention, oxygen content, etc.

[0082] (IV) New shoot rooting treatment

[0083] The rooting treatment of new shoots in each small arch shed includes: preparations before girdling → girdling → spraying hormones → filling the substrate → resuming drip irrigation → resuming covering the film cloth and sunshade net and strengthening the surroundings, etc., 6 consecutive processes. After completing all the processes of one small arch shed, the rooting treatment of new shoots in the next small arch shed can be carried out. Do not remove the shed film, sunshade net, and drip irrigation system of all small arch sheds at one time to prevent the rapid lignification of the current-year new shoots.

[0084] In other words, when there are multiple small arched sheds in the breeding nursery, when operating on one small arched shed, the remaining small arched sheds must remain covered with film. Each small arched shed completes the following operations in sequence: girdling the new shoots, spraying rooting hormones, filling the substrate, installing drip irrigation capillary tubes, restoring the film and sunshade net, and strengthening the film around the small arched shed. Thus, all operations for one small arched shed are completed; then the same operations are carried out on the next small arched shed. It is absolutely not allowed to remove the film, sunshade net, and drip irrigation system of all small arched sheds in the breeding nursery at one time (the new shoots of Zhong'ai No. 1 will age or mature quickly when growing in the open air), so as to prevent the new shoots from lignifying rapidly after being exposed to the open air due to untimely operation, resulting in the inability to take root.

[0085] (1) Preparation before girdling

[0086] One hour before girdling, remove the non-drip film, sunshade net, and drip irrigation capillary tubes of the small arched shed in sequence.

[0087] (2) Girdling the new shoots

[0088] Use a girdling knife to make a circular cut around the new shoot at a distance of 3 - 5 cm from the ground surface, and take out the tree epidermis cut off by the girdling. The purpose of girdling is: during the critical period of adventitious root primordium cell differentiation, the nutrients synthesized by the photosynthesis of the new shoot's own leaves, which are beneficial to the formation of adventitious roots, cannot flow back to the roots temporarily. At the same time, girdling can expose the wound surface, and external hormones and suitable environmental conditions can be used to promote the formation of adventitious root primordium cells at the girdling site.

[0089] The girdling time is determined as: during the critical period of cell differentiation to form adventitious root primordium cells, until the end of the critical period of adventitious root primordium cell differentiation. Preferably, the girdling operation starts in the middle and late May. If it is too early, the new shoots do not meet the requirements; if it is too late, the rooting rate is very low. The sign of the start of the critical period of adventitious root primordium cell differentiation is: when the basal diameter of the current-year new shoots of Zhong'ai No. 1 reaches 0.3 - 0.5 cm, the basal epidermis is light green, the lenticels are not obvious, the xylem color is greenish-white, the pith color is greenish-white, and there are 9 - 12 leaves, and the leaf color is light green and not mature and aged, it is the best time. When the new shoot leaves age and mature, the new shoot epidermis begins to turn brown, the lenticels appear, the xylem color is white, and the pith color is white, which indicates the end of the critical period of adventitious root primordium cell differentiation, and the girdling should be stopped immediately.

[0090] The girdling depth should be such that the cambium is not damaged. The girdling width is preferably 0.05 cm - 0.1 cm. Since the new shoots are thin, brittle, and tender during girdling, care should be taken during operation to prevent breaking the new shoots. Therefore, the girdling width should not be too wide. Damaging the cambium and having too wide a girdling width will cause the new shoots to die because the callus above and below the girdling wound cannot heal before adventitious roots grow, affecting the number and quality of new shoot roots.

[0091] (3) Spraying rooting hormones

[0092] The rooting hormone composition is: ABT No.1 powder 1200 ppm + indolebutyric acid 0.4 - 0.45 ppm. Immediately spray the hormone after girdling, evenly spray within the range of 1 - 2 cm above and below the girdling mouth in the circumferential direction of the girdling, and the spraying time for each new shoot is 1 - 1.5 s.

[0093] (4) Filling the substrate

[0094] After the hormone spraying is completed, fill the prepared mushroom stick substrate in the small arch shed area, so that the substrate is in full contact with the new shoots (especially the girdling mouth). The initial thickness of the covered substrate is 10 - 12 cm from the ground surface upwards, and then manually spray water on the substrate to make the substrate more compact and in close contact with the new shoots without gaps. After spraying water on the substrate, the final thickness is maintained at 9 - 11 cm. Too thin or too thick substrate is not conducive to regulating the temperature and humidity required for new shoot rooting.

[0095] (5) Restoring drip irrigation

[0096] After the substrate filling is completed, re - arrange the drip irrigation capillary pipes as they were originally, ensuring that there is a drip head beside each mother tree. Since the water dripping volume of the drip irrigation capillary pipe is small and cannot quickly achieve the purpose of compacting the substrate, an artificial water spraying operation (as in the previous step) is required after the substrate filling is completed. Subsequently, the humidity of the substrate in the small arch shed is controlled through the drip irrigation system.

[0097] (6) Restoring the small arch shed film and sunshade net

[0098] After the water spraying is completed, cover the plastic film and sunshade net as they were originally, press them tightly with soil in the east - west direction, and leave observation ports and ventilation ports at the north - south ends without covering them tightly.

[0099] (7) Regulating the temperature and humidity in the small arch shed to promote rooting

[0100] Temperature and humidity regulation: Place two temperature and humidity monitors at the middle position in each small arch shed. One is an air temperature and humidity monitor, and its probe is located at the top of the new shoot to monitor the temperature and humidity at the top of the new shoot. The other is a soil temperature and humidity monitor, and the tip of its probe is located at the girdling mouth inside the substrate to monitor the temperature and humidity at the girdling mouth of the new shoot inside the substrate.

[0101] The display screens of the monitoring data of the air temperature and humidity monitor and the soil temperature and humidity monitor are set outside the small arch shed, and the management personnel can monitor the temperature and humidity environment inside the small arch shed in real - time from outside the small arch shed. Achieve the set temperature and humidity requirements by regulating the dripping speed of the drip head and the size of the ventilation ports at the north - south ends.

[0102] To ensure the cell differentiation to generate adventitious roots, the temperature and humidity requirements in each small arch shed during the rooting process are as follows:

[0103] ① Requirements for air temperature and humidity in the small shed after covering with plastic film and sunshade net: Temperature from the 1st to 7th day: from 8 am to 7 pm: 31°C - 32°C; from 8 pm to 8 am the next morning: 30°C - 30.5°C. Humidity throughout the 24 hours of the day: 55 - 60%.

[0104] ② Requirements for temperature and humidity of the girdling wound substrate in the small shed after covering with plastic film and sunshade net:

[0105] Temperature from the 1st to 7th day: 31°C - 31.5°C, humidity 45 - 48%.

[0106] Since the bark of the new shoots starts to crack from the 8th day, a large amount of callus forms at the girdling wound and the bark cracking area, and cell differentiation and meristem end to form adventitious root primordia. The adventitious roots begin to enter the growth stage, and too high temperature and humidity of the substrate will affect the growth of adventitious roots. Therefore, temperature and humidity adjustment are required, as follows:

[0107] ③ Requirements for air temperature and humidity in the small shed after covering with plastic film and sunshade net: From the 8th day, temperature: 26.5°C - 28.5°C, humidity 35 - 40%.

[0108] ④ Requirements for temperature and humidity of the girdling wound substrate in the small shed after covering with plastic film and sunshade net: From the 8th day, temperature: 23 - 25°C, humidity 34 - 36%.

[0109] According to the data shown by the recorder, timely adjust the dripping speed of the drip irrigation pipe and the sizes of the air vents at the north and south ends to meet the requirements of each temperature and humidity. As the roots grow and age, from the 22nd day, the requirements for temperature and humidity of the substrate in the later growth stage of the roots are 23 - 25°C and 32 - 34%. The temperature and humidity at each stage are achieved by adjusting the water supply equipment and the ventilation openings of the small shed, etc.

[0110] During the period of mother tree planting and new shoot root promotion management in the entire small shed, pest and disease control is required. Since the new shoots have been growing in the shed and have poor drug resistance, the dosage of pesticides should be lower than that in the open air. During the period of mother tree planting and new shoot root promotion management in the entire small shed, spray a diluted solution of carbendazim 800 times + thiophanate-methyl 600 + imidacloprid 2000 times every 26 days to prevent and control various possible pests and diseases.

[0111] (8) Remove the plastic film and sunshade net

[0112] After the root promotion measures, adventitious roots will start to grow at the girdling wound and the substrate landfill area above the girdling wound after 15 days, reach the peak of rooting after 18 days, secondary roots will start to grow after 22 days, and adventitious roots will still grow until early September. It gradually stops after mid-September (4 months after girdling).

[0113] (V) Ventilation

[0114] After mid-September (about four months after girdling), ventilation around the small arch shed starts day and night, and the ventilation openings gradually increase. When the leaves of the new shoots turn to the normal color of open-field leaves and the epidermis turns brown, the plastic film and sunshade net are completely removed, and at this time, the new shoots grow normally in the open air.

[0115] (VI) Seedling lifting and temporary planting after autumn

[0116] Since the substrate uses the mushroom sticks after mushroom harvesting, mostly with wood as the raw material, it has low heat preservation and moisture retention performance in winter and poor cold resistance. To ensure that the self-rooted seedlings are not damaged by freezing, the seedlings must be lifted after the autumn leaves fall and before the soil freezes. When lifting the seedlings, dig open the substrate and cut at the girdling site to obtain the self-rooted seedlings of Zhong'ai No. 1.

[0117] After the self-rooted seedlings are lifted, they are graded and divided into three grades: large, medium, and small according to national standards, and are temporarily planted separately. The substrate is river sand. The temporary planting is carried out indoors, and the humidity of the river sand is adjusted to a water content of 35-45% with water. First, lay a layer of river sand with a width of 50 cm and a thickness of 20 cm in the temporary planting pit, then place a single layer of self-rooted seedlings, then fill in another layer of sand, and then place another layer of self-rooted seedlings. It is necessary to ensure that the sand fills the gaps between the roots of the self-rooted seedlings and the roots are in full contact with the sand. The self-rooted seedlings are temporarily planted in turn. The self-rooted seedlings can be officially transplanted into the field in the following year.

[0118] (VII) Winter management of mother trees

[0119] After the seedlings are lifted, level the substrate in each small arch shed for heat preservation and water it to ensure the safe overwintering of the mother trees. These mother trees can continue to reproduce a large number of self-rooted seedlings according to the method of the present invention in the following year, greatly reducing the cost of self-rooted seedling reproduction in the coming year.

[0120] The scheme of Application Example 1 was tested in a pear tree planting base in Hebei. The mother trees used two-year-old Pyrus betulaefolia Bunge rootstocks grafted with Zhong'ai No. 1 with a basal diameter of 2-2.5 cm; the small arch shed was covered with a sunshade net with a light transmittance of 55%. Before planting the mother trees, remove the diseased roots and damaged roots of the mother trees, retain 20 cm of the upright roots of the mother trees, and retain 15 cm of the horizontal roots. The girdling width is controlled at 0.1 cm. During the period of regulating the temperature and humidity of the small arch shed to promote root growth, as long as the air temperature and humidity and the substrate temperature and humidity fluctuate within the range of Example 1, it is not necessary to strictly maintain a constant value. Breeding Zhong'ai No. 1 self-rooted seedlings according to the above method has the following advantages compared with the current tissue culture method and layering and cutting methods:

[0121]

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements, or in the case where the technical features in the above embodiments do not conflict with each other, can be combined in the manner described in the embodiments, and these modifications, replacements or combinations do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A large-scale breeding method for self-rooted dwarfing seedlings of Zhong'ai No. 1 dwarfing pear trees with low cost, characterized in that, It includes the following steps: S1. Selection and planting of mother trees The mother trees are selected as two-year-old or older Pyrus betulifolia Bunge rootstocks grafted with Zhong'ai No. 1 with a basal diameter of 1.5 - 3 cm; the mother trees are planted after the local soil thaws, and the planting depth is such that the Zhong'ai No. 1 section is buried below the surface soil; before planting the mother trees, a small arch shed area with a north-south orientation is planned in the breeding nursery and a small arch shed skeleton without film is built in the small arch shed area, and the mother trees are planted in the planned small arch shed area; S2. Cutting the rootstock and promoting shoots After the mother trees are planted, water is applied to ensure the survival of the mother trees. After the first watering, the rootstock is cut, and the Zhong'ai No. 1 rootstock is cut off at a position 3 - 4 cm above the ground surface to promote the growth of new shoots; S3. Building a small arch shed The top of the small arch shed is covered with a film and a sunshade net with a light transmittance of 50 - 60%, ventilation openings are left at both the north and south ends, and the rest are sealed; the mother trees grow in the small arch shed from germination to before the new shoots take root; S4. Management of new shoots A drip irrigation system is used to keep the soil moisture content at 35 - 38%, water-soluble fertilizer is applied to the mother trees through the drip irrigation system, weak and slender Zhong'ai No. 1 new shoots are removed, and 2 - 3 strong new shoots are left; during this period, pest and disease control, timely weed removal and removal of Pyrus betulifolia Bunge buds are carried out in parallel; S5. Ring barking and hormone treatment of new shoots Ring barking is carried out during the critical period when new shoot cells differentiate to form adventitious root primordium cells; 1 - 3 h before ring barking, the film, sunshade net and drip irrigation system of the small arch shed are removed, a circular cut is made around the new shoot at a position 3 - 5 cm above the ground surface and the epidermis of the ring-cut new shoot is removed, the ring barking depth reaches the cambium layer and does not damage the cambium layer, and immediately after ring barking, a rooting hormone is sprayed circumferentially in the range of 1 - 2 cm above and below the ring barking opening; S6. Landfilling the substrate After the hormone spraying is completed, the substrate is landfilled in the small arch shed area and the substrate is made to be in full contact with the new shoot ring barking opening, water is sprayed to make the substrate compact and the substrate thickness is kept at 9 - 11 cm; the substrate is obtained by crushing the mushroom harvesting mushroom stick material into powder particles and then mixing and wetting it with urea and carbendazim solution; S7. Management of promoting root growth of new shoots The film, sunshade net and drip irrigation system of the small arch shed are restored to their original state, and ventilation openings are left at both the north and south ends; from the 1st to the 7th day after landfilling the substrate, the temperature and humidity of the substrate at the ring barking opening are controlled at 31 - 31.5 °C, 45 - 48%; starting from the 8th day, the temperature and humidity of the substrate at the ring barking opening are controlled at 23 - 25 °C, 34 - 36%; after 4 months, the small arch shed starts to ventilate day and night around, and when the new shoot leaves turn to the normal color of open-field leaves and the epidermis turns brown, the small arch shed is completely removed; S8. Digging out seedlings and temporary planting Before the autumn and winter leaves fall and before the soil freezes, the substrate is dug up, self-rooted seedlings are obtained by cutting at the ring barking opening, and the self-rooted seedlings are temporarily planted indoors for the winter.

2. The large-scale breeding method according to claim 1, characterized in that, In S1, before planting the mother trees, the roots of the mother trees are pruned and sorted out, including: removing the diseased roots and damaged roots of the mother trees, cutting short the overlong upright roots and horizontal roots of the mother trees, so that the upright roots are kept at 20 cm ± 2, and the horizontal roots are kept at 12 - 16 cm; after pruning and sorting out the roots of the mother trees, the pruned roots of the mother trees are soaked in a 1# rooting powder solution of 3000 ppm for 8 - 12 min, and then taken out for planting; the planting time of the mother trees is in the middle of March, and the planting depth is such that the Zhong'ai No. 1 section is buried 5 - 8 cm below the surface soil.

3. The large-scale breeding method according to claim 1, wherein Before S1, there is also S0: Plan the small arch shed area in the breeding nursery. The small arch shed is set in the north-south direction, with a single shed length of 9 - 11 meters and a width of 1.4 - 1.6 meters; Leave 0.5 - 0.55m between each small arch shed as the operation road; After planning the small arch shed area, build the small arch shed framework without film cloth in the small arch shed area; When planting the mother trees, the mother trees are planted in the planned small arch shed area, with a north-south plant spacing of 20cm ± 1 and an east-west row spacing of 34 - 36cm.

4. The large-scale breeding method according to claim 1, characterized in that, In S1, when building the small arch shed framework, arrange several small arch rings at intervals in the north-south direction, connect the small arch rings firmly with connecting rods, and set the top height of the small arch shed to 1 - 1.2m; In S3, cover the small arch shed with a non-drip film cloth, and cover the non-drip film cloth with a sunshade net with a light transmittance of 50 - 60%; Except for leaving ventilation openings at both the north and south ends, compact the non-drip film cloth and the sunshade net with soil at the other parts.

5. The large-scale breeding method according to claim 1, characterized in that, In S4, use the drip irrigation system to keep the soil moisture content at 35 - 38%. When the soil moisture content is low, turn on the deep well pump to supply water; During this period, fertilize by applying water-soluble fertilizer into the mother trees through the drip irrigation system. The water-soluble fertilizer is nitrogen: phosphorus: potassium = 10: 10:10 balanced fertilizer.

6. The large-scale breeding method according to claim 1, characterized in that, In S5, the girdling time starts in the middle and late May; The girdling width is 0.05 - 0.1cm; Immediately spray rooting hormone after girdling. The composition of the rooting hormone is 1200ppm of No. 1 rooting powder + 0.4 - 0.45ppm of indolebutyric acid; Spray evenly in the circumferential direction within the range of 1 - 2cm above and below the girdling mouth, and the spraying time of the hormone for each new shoot is 1 - 1.5s.

7. The large-scale breeding method according to claim 1, characterized in that, In S6, the substrate is to crush the mushroom stick materials after mushroom harvesting into powder particles the size of sawdust, and then evenly mix and moisten it with a solution containing 3‰ urea + 800 times carbendazim, and adjust the water content to 35 - 40% for standby.

8. The large-scale breeding method according to claim 1, wherein In S7, Requirements for air temperature and humidity in the small arch shed: From 8 am to 7 pm on the 1st - 7th day, the temperature is 31 - 32°C, from 8 pm to 8 am the next day the temperature is 30 - 30.5°C, and the humidity throughout the day is 55 - 60%; Requirements for temperature and humidity of the substrate at the girdling mouth on the 1st - 7th day: The temperature is 31 - 31.5°C, and the humidity is 45 - 48%; Starting from the 8th day, requirements for air temperature and humidity in the small arch shed: The temperature is 26.5 - 28.5°C, and the humidity is 35 - 40%; Requirements for temperature and humidity of the substrate at the girdling mouth: The temperature is 23 - 25°C, and the humidity is 34 - 36%; Starting from the 22nd day, requirements for temperature and humidity of the substrate at the girdling mouth: The temperature is 23 - 25°C, and the humidity is 32 - 34%; After 4 months, start ventilation day and night around the small arch shed. When the new shoot leaves turn to the normal color of open-field leaves and the epidermis turns brown, completely remove the plastic film and the sunshade net.

9. The large-scale breeding method according to claim 1, characterized in that In S7, during the entire new shoot root-promoting management period, spray the mother trees with a pest and disease control liquid every 26d. The composition of the pest and disease control liquid is: a diluted solution of 800 times carbendazim + 600 times thiophanate-methyl + 2000 times imidacloprid; S8 includes: After lifting the self-rooted seedlings, grade them according to the size of the self-rooted seedlings, and then conduct indoor temporary planting. The substrate for temporary planting is river sand, and the humidity of the river sand is 35 - 45%; In the temporary planting pit, lay the self-rooted seedlings alternately in the way of river sand - seedling - river sand, and complete the temporary planting of the self-rooted seedlings in turn. Ensure that the river sand fills the gaps between the roots of the self-rooted seedlings during the temporary planting process, and the roots are in full contact with the sand.

10. The large-scale breeding method according to claim 1, characterized in that, S8 also includes: after the seedlings are lifted, leveling the substrate in each small arch shed, keeping it warm and watering it to ensure the mother trees can survive the winter safely; in the following year, the mother trees are used to breed the dwarf self-rooted seedlings of Zhong'ai No. 1 pear tree in a cycle.

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