A rapid propagation method for hawthorn and crabapple

Abstract

This invention discloses a rapid propagation method for *Crassula ovata*, relating to the field of forest tree seedling propagation technology. It includes the following steps: (I) Rootstock and Scion: (1) Rootstock selection and pretreatment; (2) Scion selection and preservation; (II) High-branch grafting process: (3) Grafting location and method; (4) Interface healing regulation; (III) Post-grafting cutting system: (5) Cutting scion selection; (6) Cutting substrate and root promotion; (7) Precise environmental regulation after cutting. This invention effectively overcomes the technical bottlenecks of low propagation efficiency, poor seedling quality, and imbalance between protection and utilization in existing technologies for *Crassula ovata*, providing core technical support for the resource protection and diversified application of this rare and endangered tree species, and possessing clear practical value and industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of forest tree seedling propagation technology, and more specifically to the efficient seedling cultivation, population restoration, and large-scale propagation of superior germplasm of the rare and endangered tree species *Malus baccata* of the Rosaceae family. Background Technology

[0002] Hawthorn and crabapple ( Malus komarovii Malus (Malus) is a rare and endangered small tree endemic to China, belonging to the genus Malus in the family Rosaceae. It is a Class II protected wild plant in China, naturally distributed only in the Changbai Mountains region of Jilin Province. It possesses extremely high ecological conservation value, systematic evolutionary research value, and potential for developing distinctive forestry and fruit production. Affected by habitat fragmentation, limited natural regeneration capacity, and human disturbance, its wild population has sharply declined to endangered levels, and it has been listed in the "China Biodiversity Red List." The rescue protection and large-scale propagation of its germplasm resources have become core issues urgently needing to be addressed.

[0003] Asexual reproduction is a key technological approach for the stable preservation of superior genetic traits and the precise propagation of rare germplasm in crabapple. However, existing asexual reproduction techniques for this species are mostly limited to single grafting or single cutting methods, and lack a composite propagation system adapted to its species characteristics. This presents numerous technical bottlenecks and makes it difficult to meet the dual needs of population restoration and industrial application. Specific problems are as follows:

[0004] Firstly, the single grafting technique has extremely low propagation efficiency and insufficient stability. Current techniques mostly use Malus baccata as rootstock and employ conventional branch grafting or bud grafting processes. Although this can achieve stable inheritance of traits from the mother plant, it requires cultivating 2-year-old rootstocks first, and after grafting, it still needs 1-2 years of growth before it can be transplanted, with the entire seedling cultivation cycle lasting 3-4 years. Moreover, a single rootstock can only be grafted with 1-2 scions, resulting in extremely low utilization of scarce wild Malus baccata and Malus gracilis scion resources, making it impossible to achieve large-scale propagation. Meanwhile, existing technologies have not been optimized for the compatibility of hawthorn and crabapple rootstocks, resulting in frequent problems such as poor graft union healing and nutrient transport obstruction. The survival rate of seedlings is only 50%-60%, and their cold resistance and disease and pest resistance are weak. The survival rate of transplanted seedlings in the high-altitude native habitat of Changbai Mountain is less than 50%, which cannot meet the seedling quality standards for ecological restoration. In addition, traditional grafting requires strict manual operation techniques, has high seedling costs, and the operation window is only concentrated in the spring sap flow period. The technology has a high threshold for promotion and is not suitable for grassroots seedling units.

[0005] Secondly, single-method cutting propagation is difficult to root, has a low survival rate, and is prone to trait differentiation. Hawthorn and crabapple branches are highly lignified and have low levels of endogenous rooting hormones, making rooting extremely difficult. Even with the addition of exogenous rooting agents, existing softwood cutting techniques generally achieve a rooting rate of less than 30%. Furthermore, the root systems of cuttings are mostly fine adventitious roots without a distinct taproot, resulting in extremely poor drought and wind resistance after transplanting, with a survival rate of less than 40% after field transplanting. Simultaneously, single-method cutting carries the risk of genetic trait differentiation; some seedlings may exhibit weakened growth and decreased stress resistance, failing to retain 100% of the superior germplasm characteristics of the mother plant, which is detrimental to the precise protection of this rare resource. In addition, existing cutting techniques rely on high-precision temperature, humidity, and light control equipment, leading to high seedling costs. Moreover, the technical parameters are not customized to the physiological characteristics of hawthorn and crabapple, making stable reproduction difficult in natural seedling environments, severely limiting their practicality and universality.

[0006] Third, there are gaps in the adaptability of composite propagation technologies, and they fail to address both the needs of conservation and propagation. Existing domestic composite asexual propagation technologies for woody plants mostly employ a process of "first propagating by cuttings, then grafting for improvement," primarily serving the improvement of common fruit tree varieties. They fail to address the unique characteristics of hawthorn and crabapple species, such as "difficulty in rooting branches and special compatibility between rootstock and scion," by constructing a reverse composite propagation system of "high-branch grafting combined with cuttings." This results in the inability to directly transfer and apply existing composite technologies. Simultaneously, existing technologies in the propagation of rare and endangered tree species largely focus on static germplasm preservation (such as tissue culture preservation). However, tissue culture technology suffers from drawbacks such as long seedling cultivation cycles, low seedling survival rates, and high costs. An integrated technical solution that balances "stable preservation of traits" and "rapid mass seedling production" has long been lacking, failing to simultaneously meet the dual needs of scientific research conservation and ecological restoration.

[0007] Fourth, there is a core contradiction in the utilization of germplasm resources. As a national key protected wild plant, the collection of wild plant scions is strictly controlled by laws and regulations. However, existing propagation techniques cannot achieve efficient propagation while minimizing the consumption of wild scions, resulting in a sharp contradiction between "protecting wild resources" and "meeting propagation needs," making it difficult to balance the relationship between scientific sampling, population restoration, and resource protection.

[0008] Therefore, existing technologies cannot adapt to the biological characteristics of crabapple and are difficult to overcome the dual bottlenecks of "stable preservation of traits" and "efficient and rapid propagation". Developing a targeted and highly adaptable asexual reproduction technology has become the key to solving the crisis of crabapple germplasm resources. Summary of the Invention

[0009] In view of this, the present invention provides a method for rapid propagation of hawthorn and crabapple.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A rapid propagation method for hawthorn and crabapple trees includes the following steps: (a) Rootstock and scion (1) Rootstock selection and pretreatment: Select healthy 6-8 year old seedlings of *Malus baccata* or *Malus* with a diameter at breast height of 8-10 cm as rootstock for grafting; Rootstock pretreatment: 15-20 days before sap flow in spring, the rootstock is cut off, leaving a 60-120cm main stem; (2) Scion selection and preservation: Using superior seedlings of hawthorn and crabapple as mother plants, from November to early March of the following year, select one-year-old branches with plump and strong buds, good lignification, and no diseases or pests as scions. The length of the scion should be 15 cm. For scion preservation, after the scions are collected and cut into sections, they should be immediately wax-sealed and then stored in a low-temperature environment of -2 to -2℃. Enhanced pretreatment of scions: Before budding, the base of the scion is lightly cut and soaked in a 50 mg / L IBA solution for 3 minutes to improve the callus formation ability of the bud and rootstock and the grafting survival rate. (II) High-branch grafting technique (3) Grafting site and method: The grafting site should be selected on a healthy branch of the rootstock, 60-120cm above the ground. Choose a sunny, disease-free, and uniformly thick branch. This ensures that the bud has enough room to grow after it sprouts and also makes it easier to cut the grafted scion for propagation later. (4) Interface healing regulation: Bag protection: Immediately after grafting, cover the graft with a transparent polyethylene film bag and tie the bag opening tightly with a rope. After the leaf buds emerge, poke 3-5 small holes in the bag for ventilation, which will maintain the relative humidity of the graft union at 85%-90% and prevent mold caused by high temperature and high humidity. Environmental control: Grafting and shading, controlling the light intensity to 50%-60% of natural light, and maintaining the ambient temperature at 18-25℃; Nutrient regulation during the healing period: 10 days after grafting, spray the rootstock leaves with a 0.2% potassium dihydrogen phosphate solution once every 7 days for a total of 3 times to provide nutrient support for the healing of the graft union and shorten the healing period to 25-30 days. (III) Grafting and Cutting System (5) Cuttings for propagation: Accurately control the timing and specifications of cuttings. After the grafting interface has completely healed, continue to cultivate until the spring of the second or third year. At this time, the new shoots sprouting from the scion have grown into sufficient branches. Ensure that each grafted seedling sprouts ≥5 branches before carrying out the collection of cuttings. (6) Cutting substrate and root promotion: Given the difficulty in rooting hawthorn and crabapple, a composite cutting substrate (perlite: river sand in a 1:1 mass ratio) was used. This substrate has good air permeability, which prevents the base of the cuttings from rotting. Rooting was promoted by a combination of soaking in rooting agent and substrate disinfection. (7) Precise environmental control after cutting: Intermittent spraying combined with precise temperature and humidity control is employed. The core parameters are designed as follows: after cutting, the ambient temperature is controlled at 20-25℃, and the relative humidity is maintained at 80%-95%. An intermittent spraying mode is used, with spraying for 10 seconds and an interval of 10 minutes to prevent the cuttings from losing water and wilting. For the first 20 days after cutting, the shading rate is maintained at 70%, and after 20 days, the shading rate is gradually reduced to 50% to guide the cuttings to adapt to the light environment. At the same time, a 0.1% carbendazim solution is sprayed every 7 days for disease control to ensure that the rooting rate of cuttings is increased to over 90% and the rooting cycle is shortened to 35-40 days.

[0011] Further, in step (1), the rootstock is subjected to stress resistance pretreatment. After the branch is cut off, the cross section is coated with tree healing agent for protection and the whole plant is sprayed with low concentration of carbendazim solution for disinfection. Combined with low temperature hardening, the seedlings are cultured in an environment of 0-5℃ for 7-10 days.

[0012] Further, in step (2), the hawthorn and crabapple branches are divided into sections to extract buds, and 2-3 healthy buds can be selected from each section.

[0013] Furthermore, in step (3), the grafting method adopted is bark grafting: Bark grafting: Suitable for spring. Cut the rootstock 60-120cm above the ground, flatten the cut surface, and make a 2-3cm vertical cut along the cambium on one side. Cut the lower end of the scion into a 2-3cm long double-sided wedge shape, retaining 2 buds. Insert the scion into the bark of the rootstock, ensuring that the cambium layers are aligned. Tightly wrap the interface with plastic film, making sure the white part of the scion is exposed. Grafting should be done at the right time, ideally between the time when the sap separates from the bark and before the leaves unfold. By precisely cutting the size and smoothness of the scion, the adhesion between the cambium layers of the rootstock and scion can be improved. The binding should be neither too tight nor too loose to ensure normal respiration of the buds and subsequent germination, while avoiding propagation failure caused by poor healing of a single grafting point.

[0014] After cutting the scions, the remaining branches of the mother plant are properly pruned and shaped to promote the continued growth of new shoots, enabling repeated scion collection from a single mother plant over many years and improving the overall propagation efficiency.

[0015] Furthermore, in step (6), the rooting agent is used for soaking: before cutting, the base of the cutting is soaked in a mixed solution of 150 mg / L NAA (naphthaleneacetic acid) + 50 mg / L IBA for 3-4 hours to improve the efficiency of adventitious root induction. The substrate is disinfected by spraying it with a 0.3% potassium permanganate solution in advance, covering it with plastic film and sealing it for 24 hours, then letting it air dry for 3 days to eliminate pathogens in the substrate and reduce the risk of cutting diseases.

[0016] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. Use for the protection and population restoration of rare germplasm resources: It is used for the large-scale propagation of high-quality seedlings of Crabapple and Malus baccata, providing a stable source of seedlings for the in-situ replanting of wild populations of this endangered tree species, supporting the construction and operation of ex-situ conservation bases, effectively expanding the scale of artificial populations, alleviating the endangerment crisis of wild populations caused by insufficient natural regeneration and habitat fragmentation, realizing the rescue protection and sustainable continuation of Crabapple and Malus baccata germplasm resources, and meeting the specific technical needs in the field of biodiversity conservation.

[0017] 2. Applications in ecological restoration and native greening: The cultivated hawthorn and crabapple seedlings inherit the excellent characteristics of cold resistance and tolerance to poor soil from their mother plants. They can be directly applied to vegetation restoration, afforestation of barren mountains, and soil and water conservation projects in the high-altitude native habitat of Changbai Mountain, contributing to the restoration and reconstruction of the native ecosystem. At the same time, they can be used as a characteristic native greening tree species in cold northern regions, applied to urban and rural parks, road greening, courtyard landscapes, etc., filling the gap in the variety of winter-fruiting greening seedlings in cold regions and enhancing the diversity and stability of the regional ecological landscape.

[0018] 3. Applications in Scientific Research and Seedling Technology Promotion: Due to their clear genetic background and high trait uniformity, the cultivated seedlings can serve as standardized experimental materials for research fields such as the systematic evolution of endangered tree species of the genus Malus in the Rosaceae family, the study of stress resistance mechanisms, and the innovation and improvement of germplasm resources, providing basic support for related scientific research projects. At the same time, the seedlings cultivated by this invention and the supporting propagation technology process can be directly applied to the large-scale seedling production of forestry seedling units and grassroots forest farms, reducing seedling costs and technical barriers, promoting the standardized promotion of hawthorn and crabapple seedling technology, and meeting the technological upgrading needs of the forest tree seedling propagation industry.

[0019] 4. Specialized Industrial Development Applications: On the one hand, it provides high-quality seedlings for the construction of large-scale artificial planting bases for hawthorn and crabapple, enabling standardized harvesting of fruits and branches based on the cultivated seedlings. This supports the deep processing and development of derivative products such as functional foods (e.g., hawthorn and crabapple preserves and jams) and medicinal products (e.g., extracts based on the active ingredients of the fruit). On the other hand, leveraging the strong cold resistance and tolerance to poor soil conditions of hawthorn and crabapple, the high-quality hawthorn and crabapple seedlings cultivated in this invention can be used as dedicated rootstocks for grafting superior cold-resistant apple varieties, cultivating robust cold-resistant apple seedlings. This effectively overcomes the climatic limitations of apple cultivation in cold northern regions, expands the planting range of apples in cold areas, and improves the yield and quality of the apple industry in cold regions. Simultaneously, combining the rarity and ecological value of hawthorn and crabapple, it can create an integrated industrial model of "rootstock cultivation + cold-resistant apple planting + ecotourism + specialty product processing," contributing to rural revitalization, achieving synergistic progress in ecological protection and economic development, and meeting the application needs of upgrading specialty forestry and cold-region fruit industries.

[0020] By achieving the above-mentioned uses, this invention effectively overcomes the technical bottlenecks in the existing technology, such as low propagation efficiency of hawthorn and crabapple, poor seedling quality, and imbalance between protection and utilization. It provides core technical support for the resource protection and diversified application of this rare and endangered tree species, and has clear practical value and industrial application prospects. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 The attached figure shows a grafted seedling of Embodiment 1 of the present invention; Figure 2 The attached figure shows the cutting process of Embodiment 1 of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 Experimental materials and treatment Because *Crassula ovata* is a Class II protected plant in China, the collection of branches from the wild is limited. Therefore, the experimental material for this invention was tender shoots grown from grafted *Crassula ovata*. The experiment was conducted in April at the greenhouse of the Xinshan Nursery Cooperative in Xinshan Village, Jiangmifeng Town, Jilin City. In mid-to-late April, the tips of robust lateral branches from the upper part of the *Crassula ovata* crown were taken as cuttings. After collection, the branches were sprayed with water to maintain moisture, and scions approximately 10-15 cm in length were prepared, each retaining at least 2-3 buds.

[0025] Rootstock and scion 1. Rootstock selection and pretreatment: Based on the species characteristics of the Malus genus in the Rosaceae family and the need for adaptation to the cold northern environment, robust 6-8 year old Malus crassifolia seedlings or Malus baccata were selected as grafting rootstocks.

[0026] 6-8 year old rootstocks have sufficient nutrient accumulation to ensure the healing ability of the graft union, and can also avoid the decline in rootstock-scion compatibility caused by excessive tree age; For rootstock pretreatment, a combination of "flat-top grafting + nutrient regulation" is adopted. The rootstock is cut off 15-20 days before the sap flow in spring, and 3-4 main branches are retained for each rootstock to enhance the nutrient reserves of the rootstock. Pre-treatment of rootstocks to enhance their resistance to stress involves spraying a low-concentration carbendazim solution for disinfection after root pruning, combined with low-temperature hardening-off, and cultivation in an environment of 0-5℃ for 7-10 days to enhance the rootstocks' cold and disease resistance, laying the foundation for subsequent grafting and environmental adaptation after cutting.

[0027] 2. Scion selection and preservation: Using superior seedlings of hawthorn and crabapple as mother plants, propagation is carried out by bark grafting, with the scion buds selected to preserve trait fidelity and vigor.

[0028] Select plump buds from the current year's semi-lignified, healthy branches of the mother plant as grafting buds. The buds should be plump and free from pests and diseases. The size of the scion should be controlled to be about 15cm in length to ensure that the grafting bud has sufficient germination potential. For scion preservation, after the scions are collected and cut into sections, they should be immediately wax-sealed and then stored in a low-temperature environment of -2 to -2℃. High-branch grafting technique 3. Grafting site and method: The combined technique of high grafting and subsequent cutting propagation involves selecting a healthy branch of the rootstock 60-120cm above the ground for grafting. Priority should be given to branches that are sunny, free from pests and diseases, uniform in thickness, and 1.0-1.5cm in diameter. This ensures that the grafted bud has sufficient space to grow after sprouting and also facilitates the subsequent cutting of the grafted scion for propagation.

[0029] The grafting method primarily employs the "bark grafting" technique, and the specific operational method is as follows: Bark grafting: Suitable for spring. Cut the rootstock 60-120cm above the ground, flatten the cut surface, and make a 2-3cm vertical cut along the cambium on one side. Cut the lower end of the scion into a 2-3cm long double-sided wedge shape, retaining 2 buds. Insert the scion into the bark of the rootstock, ensuring that the cambium layers are aligned. Tightly wrap the interface with plastic film, making sure the white part of the scion is exposed. The timing of grafting is crucial; it should ideally occur between the time the sap separates from the bark and before the leaves unfold. Precise cutting of the scion, ensuring a smooth cut, enhances the adhesion between the cambium layers of the rootstock and scion. The binding should be appropriately tight to ensure normal bud respiration and subsequent germination, while also preventing propagation failure due to poor healing of a single graft union (see grafted seedlings). Figure 1 ).

[0030] 4. Interface healing regulation: In response to the slow healing speed of hawthorn and crabapple rootstocks and scions, an integrated healing regulation scheme of "bagging for moisture control + shading for temperature control + nutrient supplementation" was adopted.

[0031] Bag protection: Immediately after grafting, cover the graft with a transparent polyethylene film bag, tie the bag opening tightly with a rope, and poke 3-5 small holes in the bag for ventilation. This will maintain the relative humidity of the graft union at 85%-90% and prevent mold growth caused by high temperature and humidity. Environmental control: Grafting and shading, controlling the light intensity to 50%-60% of natural light, and maintaining the ambient temperature at 18-25℃; Nutrient regulation during the healing period: 10 days after grafting, spray the rootstock leaves with a 0.2% potassium dihydrogen phosphate solution once every 7 days for a total of 3 times to provide nutrient support for the healing of the graft union and shorten the healing period to 25-30 days.

[0032] Grafted cutting propagation system (see cutting process) Figure 2 ) 5. Cuttings for propagation: Accurately control the timing and specifications of scion cuttings. After the grafting interface has fully healed, continue cultivation until the spring of the second or third year. At this time, the new shoots sprouting from the scion have grown into sufficient branches, ensuring that each grafted seedling has sprouted ≥5 branches before carrying out the collection of cuttings.

[0033] Select robust scions: retain 2-3 plump buds on each scion, make a 45° angled cut at the base, 0.5-1cm away from the bud. At the same time, remove the lower leaves of the scion, retaining the upper 2 small leaves, and cut off 1 / 2 of the leaf area to reduce water evaporation and ensure the vigor of the scion. After selecting the scions, prune and shape the remaining branches of the mother plant to promote the continued growth of new shoots, enabling repeated scion collection from a single mother plant for many years and improving the overall propagation efficiency.

[0034] 6. Cutting substrate and root promotion: Given the difficulty in rooting hawthorn and crabapple trees, a composite cutting substrate (perlite: river sand in a 1:1 ratio) was used. This substrate has good aeration, preventing rotting at the base of the cuttings. Rooting promotion employed a combination of "rooting agent soaking + substrate disinfection": before planting, the base of the cuttings was soaked in a mixed solution of 150 mg / L NAA (naphthaleneacetic acid) and 50 mg / L IBA for 3-4 hours to improve the efficiency of adventitious root induction; the substrate was disinfected by spraying with a 0.3% potassium permanganate solution beforehand, covered with plastic film and sealed for 24 hours, then air-dried for 3 days to eliminate pathogens in the substrate and reduce the risk of cutting diseases.

[0035] 7. Precise environmental control after cutting: Intermittent spraying combined with precise temperature and humidity control is employed. The core parameters are designed as follows: after cutting, the ambient temperature is controlled at 20-23℃, and the relative humidity is maintained at 80%-85%. An intermittent spraying mode is used, with spraying for 10 seconds and an interval of 10 minutes to prevent the cuttings from losing water and wilting. For the first 20 days after cutting, the shading rate is maintained at 70%, and after 20 days, the shading rate is gradually reduced to 50% to guide the cuttings to adapt to the light environment. At the same time, a 0.1% carbendazim solution is sprayed every 10 days for disease control to ensure that the rooting rate of cuttings is increased to over 90% and the rooting cycle is shortened to 35-40 days.

[0036] Grafting propagation techniques The grafting survival rate of different treatment groups was compared using the method of this invention for grafting propagation on different rootstocks: The experimental results showed that the rootstock type had a significant impact on the grafting survival rate of *Crataegus pinnatifida* and *Crataegus tinctoria* (P<0.05). Specific survival rate data are shown in Table 1 below. Table 1. Effect of rootstock type on the survival rate of grafted hawthorn and crabapple.

[0037] Note: Different lowercase letters after the data in the same column indicate significant differences (P<0.05), and the same applies below.

[0038] As shown in Table 1, the grafting survival rate with crabapple rootstock was the highest, with a spring grafting survival rate of 87.7%, significantly higher than other rootstock types; followed by hawthorn rootstock, with a spring grafting survival rate of 82.0%; and wild hawthorn seedling rootstock had the lowest survival rate.

[0039] Scion shoot growth Table 2. New Shoot Growth

[0040] The growth of new shoots of the scion was measured 6 months after grafting. The results showed that the average length of the new shoots grafted with crabapple rootstock was 68.5±5.3cm and the thickness was 0.82±0.06cm, which was significantly better than other treatment groups. The new shoots grafted with hawthorn rootstock had a length of 57.3±4.8cm and a thickness of 0.71±0.05cm, which was the second best.

[0041] Propagation by cuttings Different rooting agents (IBA, NAA, and ABT1) were used, and different mass concentrations (100 mg·L⁻¹) were set. -1 200 mg·L -1 and 300 mg·L -1 Three mass concentrations were used for cutting propagation, with water as the control (CK).

[0042] Cuttings and Management Soak the lower end of the prepared cuttings in rooting hormone for 0.5 hours, then insert them into the sterilized substrate to a depth of about 1 / 3 of their length. Firm the soil around the cuttings and water thoroughly immediately to ensure close contact between the base and the substrate. Water regularly and weed periodically. After planting, turn on the full-light misting system to maintain high humidity (above 90%). The ideal rooting temperature is around 25°C during the day and around 15°C at night.

[0043] Rooting index determination Sixty days after cutting, the rooting rate, number of roots per cutting, and root length of each treatment group were measured and recorded, with the length accurate to 0.01 cm.

[0044] Table 3 Analysis of Cutting Test Results

[0045] The experimental results showed that 200 mg·L -1 IBA and 200 mg·L -1 ABT1 treatment showed the best effect in promoting rooting of hawthorn and crabapple cuttings, with a rooting rate exceeding 70%, which was significantly better than other treatment groups and the control.

[0046] This invention uses semi-lignified branches of *Crataegus pinnatifida* and *Crataegus pinnatifida* as cuttings to investigate the effects of different types of rooting agents (IBA, NAA, ABT1) and different mass concentrations (100 mg·L⁻¹). -1 200 mg·L -1 300mg·L -1 The effect of this treatment on the rooting efficiency of cuttings was investigated, using water as a control (CK). The optimal cutting treatment was determined by measuring four indicators: rooting rate, average number of roots, average root length, and average root diameter. The experimental results are summarized below: 1. The rooting agent treatment significantly promoted rooting of hawthorn and crabapple cuttings compared to the control: All rooting indicators in the rooting agent treatment groups were significantly higher than those in the water control group (P<0.05). The rooting rate of the control group was only 23.33±2.89%, with an average of 3.2±0.5 roots per plant, an average root length of 4.5±0.6 cm, and an average root diameter of 1.2±0.1 mm, all of which were the lowest levels among all treatments. This indicates that exogenous rooting agents can effectively overcome the rooting obstacles in hawthorn and crabapple cuttings.

[0047] 2. The promoting effects of different types of rooting agents vary: Based on four rooting indicators, IBA and ABT1 showed better promoting effects than NAA. The highest rooting rate in the IBA treatment group reached 87.33±2.89%, the highest rooting rate in the ABT1 treatment group was 83.33±2.89%, while the highest rooting rate in the NAA treatment group was only 65.00±3.33%. Furthermore, the average number of roots, average root length, and average root diameter in the IBA and ABT1 treatment groups were generally higher than those in the NAA treatment group at the same concentration.

[0048] 3. The rooting agent concentration showed a "low concentration promotes, high concentration inhibits" trend in the effect of rooting on cuttings: all three rooting agents showed a high concentration at 200 mg / L. -1 The optimal treatment effect is achieved at a high concentration (300 mg / L). -1 ) or too low (100 mg·L -1 At that time, all rooting indicators decreased. Specifically, at 200 mg·L⁻¹ -1 The IBA treatment group performed best, with a rooting rate of 87.33±2.89%, an average number of roots of 10.5±1.2 per plant, an average root length of 11.6±0.9 cm, and an average root diameter of 2.8±0.2 mm, all of which were the highest among all treatment groups; 150 mg·L -1 The ABT1 treatment group showed the second-best results, with all indicators being similar to those treated with 200 mg·L⁻¹. -1 There was no significant difference in the IBA treatment group (P>0.05), but it was significantly better than other concentration treatment groups of the same type.

[0049] 4. Optimal cutting treatment: Based on comprehensive experimental results, 200 mg·L⁻¹ -1 IBA or 200 mg / L -1 Treating hawthorn and crabapple cuttings with ABT1 for 30 minutes can significantly improve the rooting effect of cuttings, making it the optimal technical solution for hawthorn and crabapple cutting propagation and applicable in actual production.

[0050] in conclusion: The optimal combination for grafting propagation of hawthorn and crabapple is as follows: using crabapple seedlings is best, and grafting should be performed in late March using the bark grafting method. The survival rate can reach over 88.7%, and the scions grow vigorously and have strong resistance. Considering the rootstock cultivation period, hawthorn can be used as an alternative rootstock. Spring grafting has a survival rate of 82%, with excellent overall performance and a shorter cultivation period, making it more suitable for large-scale propagation. After grafting, timely removal of rootstock buds, timely untying, and setting up supports for seedlings can effectively reduce nutrient consumption, prevent wind damage, and further improve the survival rate and growth quality of grafted seedlings.

[0051] This invention uses semi-lignified branches of *Crataegus pinnatifida* and *Crataegus pinnatifida* as cuttings to investigate the effects of three rooting agents (IBA, NAA, and ABT1) and their different concentrations on rooting of cuttings, and to determine the optimal technical solution, which is 200 mg·L⁻¹. -1 IBA or 200 mg / L -1 Soak cuttings in ABT1 for 30 minutes. This provides support for large-scale seedling production. The experimental results are consistent with studies on most woody plants, and the superior effects of IBA and ABT1 are related to their mechanisms of action. 200 mg·L -1 The optimal concentration is crucial; excessively high or low concentrations are detrimental, providing flexibility for production. This method increased the rooting rate to over 88.3%, which is of great significance for the germplasm conservation and large-scale propagation of the rare and endangered Hawthorn and Crabapple. However, the experiment did not address the interaction between treatment time and other environmental factors, requiring further multi-factor experiments to optimize parameters. In practical applications, standardized selection and handling of cuttings, along with appropriate maintenance measures, are necessary to ensure seedling success.

[0052] For the Hawthorn and Crabapple populations, which suffer from severe habitat destruction and difficulty in natural recovery, priority should be given to conducting surveys of potential suitable distribution areas, establishing specialized breeding bases, achieving ex-situ conservation through introduction and domestication, and promoting naturalization trials to reduce the risk of extinction. Considering the scarcity of seedlings under Hawthorn and Crabapple forests, the application of asexual propagation techniques should be strengthened: on the one hand, the proven and feasible cutting propagation technique should be promoted, using 200 mg·L⁻¹ saturation solution. -1 IBA or 200 mg / L -1 The optimal solution for treating semi-lignified cuttings with ABT1 for 30 minutes enables rapid propagation of seedlings. On the other hand, multi-rootstock grafting experiments are conducted to utilize the stress resistance advantages of superior rootstocks such as crabapple or hawthorn to improve the survival rate and growth vigor of grafted seedlings, build a large-scale artificial propagation system, and provide sufficient seedling support for ex-situ conservation.

[0053] Full-process standardization and resource protection are compatible 1. Standardized Process Throughout: To meet the needs of industrialization and promotion, a standardized operating procedure is designed, clearly defining key parameters for each stage, such as rootstock age, scion specifications, and cutting substrate ratio. This ensures stable reproduction across different seedling production units and lowers the technical barrier. Simultaneously, a "segmented seedling cycle management" scheme is designed, breaking down the entire propagation cycle into the scion cultivation period (1-2 years), grafting healing period (25-30 days), cutting rooting period (35-40 days), and hardening-off period (45-50 days). Key management points are clearly defined for each stage, improving seedling efficiency and ensuring the overall seedling cycle is shortened to 6-8 months.

[0054] 2. Adaptation for the Protection of Rare Resources: In view of the scarcity of wild hawthorn and crabapple resources, a "minimum scion collection" scheme is designed. By cultivating scions from seedlings, using scions in segments, and then propagating them by cuttings after grafting, a single scion segment can be used to cultivate multiple seedlings, reducing the collection pressure on wild mother plants. At the same time, a mechanism for connecting artificial population propagation and wild population replenishment is designed. The cultivated seedlings are given priority for wild population replenishment and ex-situ conservation, and the remaining seedlings are used for industrial applications, achieving a balance between protection and utilization.

[0055] 3. Industrialization Extension of Rootstock: In line with the development needs of the fruit industry in cold regions, an industrialization extension plan for hawthorn and crabapple rootstocks is designed. The cultivated hawthorn and crabapple seedlings are clearly defined as suitable rootstocks for grafting cold-resistant apples (rootstock diameter ≥ 1.5cm, tree age ≥ 2 years). This ensures that after grafting with excellent cold-resistant apple varieties, the cold resistance of apples in cold regions can be improved, and they can withstand temperatures as low as -35℃. This expands the apple planting range in the cold northern regions and realizes the diversified extension of technological value.

[0056] In summary, the key design features of this invention, through precise adaptation and synergistic optimization of each stage, not only solve the core pain points of hawthorn and crabapple propagation in existing technologies, but also achieve full-chain adaptation of "protection-propagation-industrialization", providing standardized and efficient technical support for the resource protection and diversified application of this rare and endangered tree species.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rapid propagation method for hawthorn and crabapple, characterized in that, Includes the following steps: (1) Rootstock selection and pretreatment: Select healthy 6-8 year old seedlings of Malus baccata or Malus baccata as grafting rootstock. A large number of branches will emerge in 1-2 years, quickly producing propagation material. Rootstock pretreatment: 15-20 days before sap flow in spring, the rootstock is topped and the main trunk is left at 60-120cm. (2) Scion selection and preservation: Using superior seedlings of hawthorn and crabapple as mother plants, from November to early March of the following year, select one-year-old branches with plump and healthy buds, good lignification, and no diseases or pests as scions. Cut the scions into scions about 15 cm long, and each scion must retain 2-3 plump buds. Dip both ends of the scions in wax and store them at -1 to 2℃. Scion pretreatment enhancement: Before grafting, the base of the scion is lightly cut and soaked in 50 mg / L IBA solution for 3 minutes to enhance the callus formation ability of the scion and rootstock and the grafting survival rate. (3) Grafting site and method: The grafting site is selected on a healthy branch of a rootstock with a large diameter at breast height, 60-120cm above the ground. Choose a sunny, disease-free, and uniformly thick branch. This ensures that the scion has enough room to grow after sprouting and makes it easy to cut the grafted scion for cuttings later. (4) Interface healing regulation: Bag protection: Immediately after grafting, cover the graft with a transparent polyethylene film bag and tie the bag opening tightly with a rope. After the leaf buds emerge, poke 3-5 small holes in the bag for ventilation, which will maintain the relative humidity of the graft union at 85%-90% and prevent mold caused by high temperature and high humidity. Environmental control: Grafting and shading, controlling the light intensity to 50%-60% of natural light, and maintaining the ambient temperature at 18-25℃; Nutrient regulation during the healing period: 10 days after grafting, spray the rootstock leaves with a 0.2% potassium dihydrogen phosphate solution once every 7 days for a total of 3 times to provide nutrient support for the healing of the graft union and shorten the healing period to 25-30 days. (5) Cuttings for propagation: Accurately control the timing and specifications of cuttings. After the grafting interface has completely healed, continue to cultivate until the spring of the second or third year. At this time, the new shoots sprouting from the scion have grown into sufficient branches. Ensure that each grafted seedling sprouts ≥5 branches before carrying out the collection of cuttings. (6) Cutting substrate and root promotion: Given the difficulty in rooting hawthorn and crabapple, a composite cutting substrate (perlite: river sand in a 1:1 mass ratio) was used. This substrate has good air permeability, which prevents the base of the cuttings from rotting. Root promotion uses a combination of rooting agent soaking and substrate disinfection. (7) Precise environmental control after cutting: Intermittent spraying combined with precise temperature and humidity control is employed. The core parameters are designed as follows: after cutting, the ambient temperature is controlled at 20-25℃, and the relative humidity is maintained at 80%-95%. An intermittent spraying mode is used, with spraying for 10 seconds and an interval of 10 minutes to prevent the cuttings from losing water and wilting. For the first 20 days after cutting, the shading rate is maintained at 70%, and after 20 days, the shading rate is gradually reduced to 50% to guide the cuttings to adapt to the light environment. At the same time, a 0.1% carbendazim solution is sprayed every 7 days for disease control to ensure that the rooting rate of cuttings is increased to over 90% and the rooting cycle is shortened to 35-40 days.

2. The rapid propagation method according to claim 1, characterized in that, Step (1) also includes rootstock stress resistance pretreatment, applying tree healing agent to the cut surface of the branch after the top is cut off for protection, and spraying the whole plant with low concentration of carbendazim solution for disinfection, combined with low temperature hardening, and cultivating in an environment of 0-5℃ for 7-10 days.

3. The rapid propagation method according to claim 1, characterized in that, Step (2) Take buds from hawthorn and crabapple branches in sections, and select 2-3 healthy buds from each section.

4. The rapid propagation method according to claim 1, characterized in that, Step (3) The grafting method adopted is bark grafting: Bark grafting: Suitable for spring. Cut the rootstock 60-120cm above the ground, flatten the cut surface, and make a 2-3cm vertical cut along the cambium on one side. Cut the lower end of the scion into a 2-3cm long double-sided wedge shape, retaining 2 buds. Insert the scion into the cut of the rootstock, ensuring that the cambium layers are aligned. Tightly wrap the interface with plastic film, leaving the scion bud exposed.

5. The rapid propagation method according to claim 4, characterized in that, The specific operation method for the bark grafting is as follows: Step 1, rootstock incision preparation: Flatten the cross-section with a sterilized grafting knife, and make a 2-3cm vertical cut along the cambium on one side, with a cut length of 1.5-2.0cm and a depth reaching the xylem but without damaging it; gently lift the phloem on both sides of the cut with the tip of the grafting knife to facilitate scion insertion, and be careful to avoid touching the inner wall of the cut during the operation to prevent contamination; The second step is to prepare the scion: cut the lower end of the scion into a 2-3cm long double-sided wedge shape, and retain 2-3 buds; The third step is bud insertion and binding: Quickly insert the prepared scion into the bark of the rootstock, ensuring that both sides of the cut surface of the scion are in close contact with the phloem of the rootstock without any gaps; then use plastic binding tape to bind it spirally upwards from 1cm below the cut, with moderate tightness during the binding process, ensuring that the scion and rootstock are in close contact while avoiding pressure on the bud, and finally exposing the bud, binding and sealing all other cut areas to prevent moisture loss and pathogen invasion; By precisely matching the incision size with the bud patch specifications, the adhesion between the cambium layers of the rootstock and scion is improved; the exposed bud binding method is adopted to ensure normal bud respiration and subsequent germination, while avoiding propagation failure caused by poor healing of a single grafting interface.

6. The rapid propagation method according to claim 1, characterized in that, Step (5) Cut healthy scions: Keep 2-3 plump buds on the scion, cut the base at a 45° angle, and cut 0.5-1cm away from the bud. At the same time, both ends of the scion must be dipped in wax to reduce water evaporation and ensure the viability of the scion. After cutting the scions, prune and shape the remaining branches of the mother plant in a reasonable way to promote the continued sprouting of new shoots, so as to realize the repeated collection of scions from a single mother plant for many years and improve the overall propagation efficiency.

7. The rapid propagation method according to claim 1, characterized in that, Step (6) involves soaking the cuttings in a rooting agent: before planting, the base of the cuttings is soaked in a mixed solution of 150 mg / L NAA (naphthaleneacetic acid) + 50 mg / L IBA for 3-4 hours to improve the efficiency of adventitious root induction. The substrate is disinfected by spraying it with a 0.3% potassium permanganate solution in advance, covering it with plastic film and sealing it for 24 hours, then letting it air dry for 3 days to eliminate pathogens in the substrate and reduce the risk of cutting diseases.

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