Seedling raising method for improving grafting survival rate of phoebe bournei

Abstract

The invention relates to the technical field of forest tree genetic breeding and propagation, and particularly discloses a seedling raising method for improving the grafting survival rate of phoebe bournei. Comprising the following steps: S1, cultivating phoebe bournei cutting seedlings as rootstocks, and keeping the rootstocks in a robust state for later use; s2, semi-lignified branches growing in the current season are collected from the excellent phoebe bournei stock plants to serve as scions; s3, performing disinfection and pretreatment on the scions to prepare scion sections with wedge-shaped notches; s4, cutting off and cutting the stock, and combining the scions treated in the step S3 with the stock to enable cambiums to be aligned; s5, sealing and fixing the grafting joint part by using a binding belt material; s6, performing stage moisturizing and light and temperature regulation and control on the grafted plants. The seedling raising method can be applied to the fields of efficient germplasm resource utilization, artificial forest and landscape forest construction and the like, and has the advantages that the grafting survival rate is high and stable, the interface healing speed is high, the quality is good, and nursery stocks grow robustly and neatly.

Description

Technical Field

[0001] This application relates to the field of forest tree genetics, breeding and propagation technology, and more specifically, it relates to a seedling cultivation method to improve the grafting survival rate of Phoebe bournei. Background Technology

[0002] In the field of forest tree genetics, breeding, and propagation technology, grafting of Phoebe zhennan is used as an asexual reproduction method. Its application lies in the complete fixation and efficient replication of the superior traits of strictly selected mother trees, thereby overcoming the bottleneck of severe trait segregation and slow improvement of varieties in offspring propagated from seed. Its advantages are reflected in the fact that it can not only maintain 100% of the genetic gain of the mother tree, realizing the large-scale rapid propagation and early promotion of superior clones, but also improve the resistance and adaptability of seedlings by using highly adaptable rootstocks, and significantly shorten the breeding cycle, providing reliable technical support for the genetic improvement, germplasm resource preservation, and high-efficiency artificial forest construction of Phoebe zhennan.

[0003] The grafting of *Machilus chinensis* involves using seedlings as rootstock and cuttings from superior mother plants as scions. Conventional cleft grafting or whip grafting methods are employed. However, the diverse sources of rootstocks lead to variations in their genetic background, physiological state, and pest and disease carriage. Furthermore, the lignification, nutritional status, and disinfection treatment of the scions are often rudimentary. This results in difficulty for the cambium layers of the rootstock and scion to align and heal quickly and adequately, leading to low vascular connection efficiency and easy water loss or infection at the graft union. Consequently, the grafting survival rate is low and unstable, and seedling growth is inconsistent, making it difficult to meet the industry's demand for efficient and large-scale propagation of superior clonal lines. Summary of the Invention

[0004] To address the issues of low and unstable grafting survival rates and poor seedling growth uniformity caused by using wild seedlings as rootstock in the grafting of Phoebe zhennan, this application provides a seedling cultivation method to improve the grafting survival rate of Phoebe zhennan.

[0005] This application provides a method for improving the survival rate of grafted *Phoebe zhennan* seedlings, employing the following technical solution: A method for improving the survival rate of grafted *Machilus chinensis* seedlings includes the following steps: S1. Cultivate *Machilus pungens* cuttings as rootstock, and wait for the rootstocks to grow into a robust state for use; S2. Collect semi-lignified branches that sprout in the current season from superior Phoebe bournei mother plants as scions; S3. Disinfect and pre-treat the scion to prepare scion segments with wedge-shaped cuts; S4. Cut and incise the rootstock, and combine the scion treated in step S3 with the rootstock to align the cambium layers. S5. Use binding material to seal and fix the grafting joint; S6. After grafting, maintain moisture and regulate light and temperature in stages until the scion grows stably.

[0006] By adopting the above technical solutions, the rootstock has the characteristics of genetic consistency and freedom from pests and diseases, providing a stable basic material for grafting; the semi-lignified scion collected from superior mother plants contains abundant endogenous hormones and nutrients, which are conducive to interface healing; the wedge-shaped incision design increases the contact area between the cambium layers of the rootstock and scion, enabling the vascular tissues to establish connections more quickly; the sealing and fixing operation prevents moisture loss and pathogen invasion at the interface; and the subsequent staged environmental control promotes the smooth transition and healthy growth of the grafted body by simulating suitable growth conditions, thereby improving the grafting survival rate.

[0007] Preferably, in step S1, the rootstock is cultivated in a substrate composed of leaf mold, vermiculite and river sand in a volume ratio of 1.8~2.2:0.8~1.2:0.8~1.2.

[0008] By adopting the above technical solution, leaf mold provides abundant organic matter and trace elements, which can continuously supply the nutrients required for rootstock growth; vermiculite has water retention and ion exchange capacity, which can regulate the balance of water and nutrients in the substrate; river sand increases the aeration and drainage of the substrate, preventing water accumulation and rot of the roots; the substrate formed by mixing the three materials in a specific ratio has structural stability, water retention capacity and aeration characteristics, providing an ideal environment for the healthy development of rootstock roots, and providing rootstock materials in good physiological condition for subsequent grafting.

[0009] Preferably, in step S1, the rootstock is cultivated for 20 to 24 months, and the seedling height at grafting is 30 to 45 cm, and the ground diameter is 3.5 to 5.5 mm.

[0010] By adopting the above technical solution, the cultivation period of 20 to 24 months ensures that the rootstock reaches a suitable physiological maturity and that the root system is fully developed. At this time, the cambium cells are actively dividing, which is conducive to the healing process after grafting. The rootstock with a height of 30 to 45 cm has sufficient mechanical strength to support the growth of the scion and facilitates the grafting operation. The stem thickness of 3.5 to 5.5 mm can ensure that the cambium has sufficient contact area and avoid grafting difficulties caused by stems that are too thick or too thin. The synergistic effect of the above parameters provides conditions for the healing of the graft union.

[0011] Preferably, in step S2, the superior *Phoebe zhennan* mother tree has a tree height greater than the average tree height by 20% and a diameter at breast height (DBH) greater than the average tree diameter by 45%.

[0012] By adopting the above technical solutions, mother plants with height and diameter at breast height above average usually have stronger growth vigor and stress resistance, and their genetic traits are excellent. Scions collected from such mother plants contain richer nutrients and hormones, and have higher cell division activity. These characteristics enable the scions to establish physiological connections with the rootstock more quickly after grafting, improve the quality of interface healing, and ensure the stable inheritance and expression of excellent traits.

[0013] Preferably, in step S2, the diameter of the base of the collected scion is ≥3.0mm; the scion can be wrapped with moist moss and stored at 4-8℃ for no more than 3 days.

[0014] By adopting the above technical solutions, scions with a base diameter ≥3.0mm have a relatively robust tissue structure and a certain reserve of nutrients, which can support the initial growth needs after grafting; the wet moss wrapping can maintain an appropriate humidity environment for the scions and prevent them from wilting due to water loss; the low temperature storage conditions of 4-8℃ can effectively reduce the respiration and metabolic rate of the scions and reduce the consumption of nutrients; the subsequent storage period of no more than 3 days ensures that the scions are used for grafting in the best physiological condition and avoids the decline in vitality caused by long-term storage.

[0015] Preferably, in step S3, the scion is trimmed to a length of 3.5–5.5 cm, retaining at least two buds, and slanted cuts of 1.5–2.5 cm are made on both sides of the base.

[0016] By adopting the above technical solution, the length of 3.5 to 5.5 cm ensures that the scion has sufficient nutrient reserves and facilitates fixation during grafting. Retaining at least two buds ensures that the scion has strong germination potential, and even if one bud is damaged, the other bud can still germinate normally. The slanted cut design on both sides of the base maximizes the exposed area of ​​the cambium. The cut length of 1.5 to 2.5 cm matches the cut depth of the rootstock, ensuring that the cambium can fully contact the rootstock when the scion and rootstock are combined, promoting the rapid formation of callus tissue and the effective connection of the vascular system.

[0017] Preferably, in step S3, the disinfection treatment involves soaking the affected area in a plant essential oil compound disinfectant with a volume concentration of 0.05% to 0.15% for 2 to 4 minutes.

[0018] By adopting the above technical solution, a plant essential oil compound disinfectant with a volume concentration of 0.05% to 0.15% has suitable bactericidal activity, which can kill pathogenic microorganisms on the surface of the scion while avoiding damage to the plant tissue. The subsequent soaking time of 2 to 4 minutes ensures that the disinfectant can fully contact and remove the pathogens on the surface, while avoiding damage to the plant tissue due to excessive treatment time. This treatment method creates sterile starting conditions for grafting and reduces the risk of infection at the graft union.

[0019] Preferably, the plant essential oil compound disinfectant contains tea tree oil or eucalyptus oil.

[0020] By adopting the above technical solutions, the terpenoids in tea tree oil and the eucalyptol in eucalyptus oil have broad-spectrum antibacterial properties, which can inhibit the growth of a variety of plant pathogens. These natural plant essential oils are relatively safe for plant tissues at appropriate concentrations, avoiding the risk of harmful residues caused by the use of chemical disinfectants. Their use ensures disinfection effect while avoiding adverse effects on the callus formation ability of scions.

[0021] Preferably, in step S4, the rootstock is cut off 12-18 cm above the base and a 1.5-2.5 cm deep incision is made diagonally downward along one side of the cut surface.

[0022] By adopting the above technical solution, cutting the rootstock 12-18cm above the base avoids aging tissues or diseased / insect-infested areas, allowing for the selection of physiologically active stem segments for grafting. The downward slanted cut facilitates the stable insertion of the scion, and the 1.5-2.5cm depth of the cut is coordinated with the length of the slanted cut on the scion, ensuring maximum alignment and contact of the cambium layers. This cut design reduces mechanical stress on the graft union, providing conditions for rapid healing of the rootstock and scion.

[0023] Preferably, step S6 includes: first stage: after grafting, build an arched shed and cover it with a light-transmitting film, maintain the humidity inside the shed at 80% to 88%, the temperature at 22 to 28°C, and spray once every 5 to 8 days; second stage: after the scion sprouts, gradually uncover the film for ventilation and apply foliar fertilizer mainly composed of phosphorus and potassium fertilizer.

[0024] By adopting the above technical solution, the high humidity environment in the first stage reduces water transpiration from the scion, and the temperature range of 22-28℃ promotes callus formation. The light-transmitting film maintains humidity while allowing appropriate photosynthesis, and regular spraying replenishes water requirements. In the subsequent second stage, the grafted body adapts to the external environment by gradually removing the film, and the application of phosphorus and potassium fertilizers promotes the lignification and vigorous growth of new shoots. This phased management ensures a smooth transition of the grafted body from the healing period to the growth period and improves the survival stability.

[0025] In summary, this application has the following beneficial effects: 1. Since this application uses cuttings to cultivate rootstocks and collects semi-lignified scions from superior mother plants, the genetic consistency and disease-free characteristics of the rootstocks cultivated from cuttings are combined with the rich endogenous hormones and nutrients in the scions. Subsequently, the wedge-shaped incision is used to increase the contact area of ​​the cambium and to seal and fix it to prevent moisture loss. Furthermore, the appropriate growth conditions are simulated through staged environmental regulation. The synergistic effect of the above steps is to improve the healing speed of the grafting interface, the efficiency of vascular connection, and the overall survival rate.

[0026] 2. In this application, it is preferred to use a substrate made of leaf mold, vermiculite and river sand mixed in a specific volume ratio to cultivate rootstocks, and to control the cultivation time and seedling height and diameter parameters. This substrate formula provides a balance of nutrients, water retention and aeration, and is compatible with the physiological maturity and mechanical strength requirements of the rootstock to obtain rootstock material with strong root system and active cambium, providing a stable foundation for grafting healing.

[0027] 3. The method of this application involves disinfecting the scion with plant essential oils and preparing a wedge-shaped incision, cutting and incising the rootstock at a suitable position, and combining two stages of moisturizing and light and temperature control after grafting. The disinfection treatment reduces the risk of infection, the incision design promotes cambium alignment, and the staged management ensures the transition from the healing period to the growth period. Therefore, the grafted body achieves rapid healing, smooth germination, and robust growth. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating a method for improving the survival rate of grafted *Phoebe zhennan* seedlings proposed in this application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Example 1: A method for improving the survival rate of grafted *Machilus chinensis* seedlings, comprising the following steps: S1. Cultivate *Machilus pungens* cuttings as rootstock, and wait for the rootstocks to grow into a robust state for use; The rootstock was cultivated in a substrate composed of leaf mold, vermiculite and river sand in a volume ratio of 1.8:0.8:0.8 for 20 months. The seedlings were 30cm tall and 3.5mm in diameter at grafting.

[0031] S2. Collect semi-lignified branches that sprout in the current season from superior Phoebe bournei mother plants as scions; Among them, the height of the superior Phoebe bournei mother trees is 21% greater than the average tree height and the diameter at breast height is 46% greater than the average tree diameter. The diameter of the base of the collected scions is 3.0 mm. The scions are wrapped in moist moss and stored at 4℃ for no more than 2 days.

[0032] S3. Disinfect and pre-treat the scion to prepare scion segments with wedge-shaped cuts; The scion is pruned to a length of 3.5cm, retaining at least two buds, and slanted cuts of 1.5cm length are made on both sides of the base. The disinfection treatment is to soak the scion in a 0.05% volume concentration of plant essential oil compound disinfectant for 2 minutes. This plant essential oil compound disinfectant contains tea tree oil.

[0033] S4. Cut and incise the rootstock, and combine the scion treated in step S3 with the rootstock to align the cambium layers. Specifically, the rootstock is cut off 12cm above the base, and a 1.5cm deep incision is made diagonally downwards along one side of the cut surface.

[0034] S5. Use binding material to seal and fix the graft union.

[0035] S6. After grafting, the plant should be kept moist and the light and temperature should be controlled in stages until the scion grows stably. The process is as follows: First stage: After grafting, build an arched shed and cover it with a light-transmitting film to maintain the humidity inside the shed at 80% and the temperature at 22℃, and spray once every 5 days; Second stage: After the scion sprouts, gradually uncover the film for ventilation and apply foliar fertilizer mainly composed of phosphorus and potassium fertilizer.

[0036] Example 2: A method for improving the survival rate of grafted *Machilus chinensis* seedlings, comprising the following steps: S1. Cultivate *Machilus pungens* cuttings as rootstock, and wait for the rootstocks to grow into a robust state for use; The rootstock was cultivated in a substrate composed of leaf mold, vermiculite and river sand in a volume ratio of 2.0:1.0:1.0 for 22 months. The seedlings were 40cm tall and 4.5mm in diameter at grafting.

[0037] S2. Collect semi-lignified branches that sprout in the current season from superior Phoebe bournei mother plants as scions; Among them, the height of the superior Phoebe bournei mother trees is 25% greater than the average tree height and 50% greater than the average tree diameter at breast height. The diameter of the base of the collected scions is 4.5 mm. The scions are wrapped in moist moss and stored at 6℃ for no more than 3 days.

[0038] S3. Disinfect and pre-treat the scion to prepare scion segments with wedge-shaped cuts; The scion is pruned to a length of 4.5cm, retaining at least two buds, and slanted cuts of 2.0cm length are made on both sides of the base. The disinfection treatment is to soak the scion in a 0.10% volume concentration of plant essential oil compound disinfectant for 3 minutes. This plant essential oil compound disinfectant contains eucalyptus oil.

[0039] S4. Cut and incise the rootstock, and combine the scion treated in step S3 with the rootstock to align the cambium layers. Specifically, the rootstock is cut off 15cm above the base, and a 2.0cm deep incision is made diagonally downwards along one side of the cut surface.

[0040] S5. Use binding material to seal and fix the graft union.

[0041] S6. After grafting, the plant should be kept moist and the light and temperature should be controlled in stages until the scion grows stably. The process is as follows: First stage: After grafting, build an arched shed and cover it with a light-transmitting film to maintain a humidity of 84% and a temperature of 25℃ inside the shed, and spray once every 6 days; Second stage: After the scion sprouts, gradually uncover the film for ventilation and apply foliar fertilizer mainly composed of phosphorus and potassium fertilizer.

[0042] Example 3: A method for improving the survival rate of grafted *Machilus chinensis* seedlings, comprising the following steps: S1. Cultivate *Machilus pungens* cuttings as rootstock, and wait for the rootstocks to grow into a robust state for use; The rootstock was cultivated in a substrate composed of leaf mold, vermiculite and river sand in a volume ratio of 2.2:1.2:1.2 for 24 months. The seedlings were 55cm tall and 5.5mm in diameter at grafting.

[0043] S2. Collect semi-lignified branches that sprout in the current season from superior Phoebe bournei mother plants as scions; Among them, the height of the superior Phoebe bournei mother trees is 30% greater than the average tree height and 55% greater than the average tree diameter at breast height. The diameter of the base of the collected scions is 5.0 mm. The scions are wrapped in moist moss and stored at 8℃ for no more than 3 days.

[0044] S3. Disinfect and pre-treat the scion to prepare scion segments with wedge-shaped cuts; The scion is pruned to a length of 5.5cm, retaining at least two buds, and slanted cuts of 2.5cm length are made on both sides of the base. The disinfection treatment is to soak the scion in a 0.15% volume concentration of plant essential oil compound disinfectant for 4 minutes. This plant essential oil compound disinfectant contains a mixture of tea tree oil and eucalyptus oil.

[0045] S4. Cut and incise the rootstock, and combine the scion treated in step S3 with the rootstock to align the cambium layers. The rootstock is cut off 18cm above the base and a 2.5cm deep incision is made diagonally downwards along one side of the cut surface.

[0046] S5. Use binding material to seal and fix the graft union.

[0047] S6. After grafting, the plant should be kept moist and the light and temperature should be controlled in stages until the scion grows stably. The process is as follows: First stage: After grafting, build an arched shed and cover it with a light-transmitting film to maintain the humidity inside the shed at 88% and the temperature at 28℃, and spray once every 8 days; Second stage: After the scion sprouts, gradually uncover the film for ventilation and apply foliar fertilizer mainly composed of phosphorus and potassium fertilizer.

[0048] Comparative Example 1: This comparative example refers to the content of Example 1, except that the rootstock is cultivated in a substrate composed of leaf mold, vermiculite and river sand in a volume ratio of 2.34:0.8:0.8. The rest of the content is the same as Example 1.

[0049] Comparative Example 2: This comparative example is the same as that in Example 1, except that the rootstock was cultivated for 4.9 months.

[0050] Comparative Example 3: This comparative example refers to the content of Example 1, except that the diameter of the base of the collected scion is 2.8 mm, and the rest of the content is the same as that of Example 1.

[0051] Comparative Example 4: This comparative example refers to the content of Example 1, except that the disinfection treatment is to soak in a 0.02% volume concentration of plant essential oil compound disinfectant for 2 minutes, and the rest is the same as Example 1.

[0052] Comparative Example 5: This comparative example refers to the content of Example 1, except that 1.0 cm long oblique cuts are made on both sides of the base of the scion. The rest of the content is the same as Example 1.

[0053] Comparative Example 6: This comparative example refers to the content of Example 1, except that the humidity inside the greenhouse is maintained at 56% in the first stage, and the rest of the content is the same as Example 1.

[0054] Performance testing Sample Preparation: The sample groups required for the performance testing included: an experimental group prepared using the method of this application, namely, one group of grafted seedlings each operated according to Examples 1-3, with 50 seedlings in each group; and a control group prepared using the comparative scheme, namely, one group of grafted seedlings each operated according to Comparative Examples 1-6, with 50 seedlings in each group. After grafting, all grafted seedlings in all groups were managed uniformly under the same environmental conditions that conformed to the conventional growth conditions of *Phoebe zhennan* until the end of the testing period.

[0055] Grafting survival rate test: After grafting, observe and record the budding and growth of the scion regularly; the test period is set to the 120th day after grafting. Count the number of plants in each group with obvious budding of the scion and new branches with a length of more than 2 cm, and calculate the percentage of the total number of grafted plants. This is the grafting survival rate at that time point; the test standard for performance parameters is: grafting survival rate (%) = (number of surviving plants / total number of grafted plants) × 100%, referring to the evaluation method for the survival of grafted seedlings in the "Guide to DUS Testing of New Forest Plant Varieties: Mahogany" (LY / T2587-2016).

[0056] Interface healing index test: On the 30th day after grafting, 10 grafted seedlings were randomly selected from each group, the binding was carefully removed, and the formation of callus tissue at the interface was observed. The degree of interface healing was quantified by a scoring method: 0 points indicated no callus formation and the interface was dry and shriveled; 1 point indicated a small amount of callus formation with a contact area of ​​less than 25%; 2 points indicated moderate callus formation with a contact area between 25% and 50%; 3 points indicated good callus formation with a contact area between 50% and 75%; 4 points indicated sufficient callus formation, a smooth and full interface, and a contact area greater than 75%. The average score of each group was calculated as the interface healing index. Test standard for performance parameters: Interface healing index (0-4 points), the scoring standard is based on the general method for morphological observation of plant grafted callus tissue.

[0057] Grafted seedling growth index testing: On the 120th day after grafting, the length of new shoots and the number of new leaves of all surviving plants in each group were measured; the length of new shoots was measured with a tape measure from the graft union to the tip of the new shoot, accurate to 0.1 cm; the number of new leaves was the total number of fully sprouted and unfolded leaves on the scion; the average length of new shoots and the average number of new leaves of each group were calculated; the test standards for performance parameters were as follows: the measurement of new shoot length (cm) was in accordance with the method for measuring seedling height in "Grading of Forest Tree Seedlings" (GB6000-1999); the number of new leaves (pieces) was directly counted.

[0058] Disease resistance testing of grafted seedlings: In the second stage after grafting, common pathogens affecting the leaves of *Machilus chinensis* were artificially inoculated in the cultivation environment, and suitable humidity conditions for disease development were maintained after inoculation. On the 7th and 14th days after inoculation, the number and expansion of lesions on the new shoots and leaves of each group of grafted seedlings were observed and recorded, and the disease index was obtained. The disease index was divided into level 0 (no lesions) to level 4 (severe lesions, yellowing and wilting of leaves), and the average value of each group was calculated. The test standards for performance parameters: Disease index (level 0-4), inoculation identification and grading standards refer to the relevant parts of the "Guidelines for Field Efficacy Trials of Pesticides".

[0059] Table 1: Comparison of Detection Data between Examples and Comparative Examples

[0060] Example Conclusion: Based on Examples 1-3 and Comparative Example 1, and in conjunction with Table 1, it can be seen that when the proportion of leaf mold in the seedling substrate exceeds the reasonable range, it will disrupt the structural balance and aeration of the substrate, thereby weakening the development foundation of the rootstock root system, leading to a decline in the rootstock's vitality and healing ability, and making it unable to provide stable water and nutrient support for the scion, ultimately affecting the graft union healing quality, initial growth vitality, and overall survival stability of the graft.

[0061] Based on Examples 1-3 and Comparative Example 2, and in conjunction with Table 1, it can be seen that insufficient rootstock cultivation time will affect its physiological maturity, resulting in insufficient cambium cell division and insufficient stem mechanical tissue, making it difficult to quickly establish effective vascular connections with the scion, delaying the formation and differentiation of callus tissue at the graft union, and reducing the synergistic healing efficiency and seedling vigor of grafting.

[0062] Based on Examples 1-3 and Comparative Example 3, and in conjunction with Table 1, it can be seen that a small diameter at the base of the scion means that it has insufficient stored nutrients and an inadequate tissue structure. During the critical period from grafting to self-sufficiency, the scion is prone to decline in vitality due to energy deficiency, and its cambium activity and stress resistance are also weakened. Consequently, the grafted body heals slowly, new shoots sprout weakly, and disease resistance deteriorates.

[0063] Based on Examples 1-3 and Comparative Example 4, and in conjunction with Table 1, it can be seen that if the concentration of disinfectant is too low, it cannot effectively kill the pathogenic microorganisms carried on the surface of the scion. In the high humidity environment after grafting, pathogens are prone to grow and multiply, which not only infects the callus tissue at the graft union and hinders its normal formation, but also causes subsequent disease problems, thereby destroying the grafting success rate from the source and weakening the overall health level of the seedlings.

[0064] As can be seen from Examples 1-3 and Comparative Example 5 and Table 1, insufficient length of the wedge-shaped incision on the scion limits the contact area between the cambium layers of the rootstock and the scion, reduces the space and opportunity for callus tissue to grow interactively, makes it difficult for the channels for water and nutrients to be connected smoothly, resulting in weak healing at the graft union, low material transport efficiency, and hindered scion growth.

[0065] Based on Examples 1-3 and Comparative Example 6, and in conjunction with Table 1, it can be seen that if the environmental humidity is too low in the initial stage after grafting, it will aggravate the transpiration of water from the scion, causing it to wilt due to water loss before it can establish a reliable water connection with the rootstock, resulting in loss of cell activity and ultimately failure of callus induction. This indicates that maintaining a high humidity environment in the early stage has an impact on ensuring grafting survival.

[0066] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for improving the survival rate of grafted *Phoebe zhennan* seedlings, characterized in that, Includes the following steps: S1. Cultivate *Machilus pungens* cuttings as rootstock, and wait for the rootstocks to grow into a robust state for use; S2. Collect semi-lignified branches that sprout in the current season from superior Phoebe bournei mother plants as scions; S3. Disinfect and pre-treat the scion to prepare scion segments with wedge-shaped cuts; S4. Cut and incise the rootstock, and combine the scion treated in step S3 with the rootstock to align the cambium layers. S5. Use binding material to seal and fix the grafting joint; S6. After grafting, maintain moisture and regulate light and temperature in stages until the scion grows stably.

2. The method for improving the survival rate of grafted *Machilus chinensis* according to claim 1, characterized in that, In step S1, the rootstock is cultivated in a substrate composed of leaf mold, vermiculite and river sand in a volume ratio of 1.8~2.2:0.8~1.2:0.8~1.

2.

3. The method for improving the survival rate of grafted *Machilus pungens* according to claim 1, characterized in that, In step S1, the rootstock is cultivated for 7 to 9 months, and the seedling height at grafting is 45 to 65 cm, and the ground diameter is 4.5 to 6.5 mm.

4. The method for improving the survival rate of grafted *Machilus chinensis* according to claim 1, characterized in that, In step S2, the superior Phoebe zhennan mother trees have a tree height greater than the average tree height by 20% and a diameter at breast height greater than the average tree diameter by 45%.

5. The method for improving the survival rate of grafted *Machilus pungens* according to claim 1, characterized in that, In step S2, the diameter of the base of the collected scion must be ≥4.0 mm; the scion must be wrapped in moist moss and stored at 4–8℃ for no more than 5 days.

6. The method for improving the survival rate of grafted *Machilus pungens* according to claim 1, characterized in that, In step S3, the scion is trimmed to a length of 3.5–5.5 cm, retaining at least two buds, and slanted cuts of 1.5–2.5 cm are made on both sides of the base.

7. The method for improving the survival rate of grafted *Machilus pungens* according to claim 1, characterized in that, In step S3, the disinfection treatment involves soaking the affected area in a plant essential oil compound disinfectant with a volume concentration of 0.05% to 0.15% for 2 to 4 minutes.

8. A method for improving the survival rate of grafted *Machilus chinensis* according to claim 7, characterized in that, The plant essential oil compound disinfectant contains tea tree oil or eucalyptus oil.

9. The method for improving the survival rate of grafted *Machilus chinensis* according to claim 1, characterized in that, In step S4, the rootstock is cut off 12-18 cm above the base, and a 1.5-2.5 cm deep incision is made diagonally downward along one side of the cut surface.

10. A method for improving the survival rate of grafted *Machilus pungens* according to claim 1, characterized in that, The S6 step includes: First stage: After grafting, build an arched shed and cover it with a light-transmitting film to maintain the humidity inside the shed at 80% to 88% and the temperature at 22 to 28°C, and spray once every 5 to 8 days; Second stage: After the scion sprouts, gradually uncover the film for ventilation and apply foliar fertilizer mainly composed of phosphorus and potassium fertilizer.

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