A method for cultivating yellow-branched Chinese fir by grafting and dwarfing seedlings

Abstract

This invention relates to a method for cultivating dwarf seedlings of *Kaloula chinensis* through grafting, belonging to the field of asexual plant reproduction technology. The method includes the following steps: selecting *Kaloula chinensis* seedlings with a ground diameter of 0.5–1.0 cm as rootstock, selecting superior one-year-old branches of *Kaloula chinensis* as scions, grafting the rootstock and scions in March, and managing them after grafting. This invention overcomes the bottleneck of seed or cutting propagation of *Kaloula chinensis*, achieving a grafting survival rate of over 90%. The grafting process is simple, the cultivation time is short, and seedlings can be transplanted in the winter of the same year or the following spring. It solves the problems of slow seed propagation and low yield of *Kaloula chinensis*, providing a scientific reference for the construction of dwarf clonal seed orchards of *Kaloula chinensis*.

Description

Technical Field

[0001] This invention relates to the field of asexual reproduction technology of plants, specifically to a method for cultivating dwarf seedlings by grafting *Fir chinensis*. Background Technology

[0002] In terms of the cultivation of *Fir chinensis* seedlings, only some seed propagation and cutting propagation are available. Due to the low flowering and fruiting of the mother trees, poor seed development, and weak natural regeneration ability, coupled with the large size of the mother trees, seed collection and seedling cultivation are extremely difficult. In addition, the seed quality and germination rate are low, and the propagation speed of sowing and seedling cultivation is slow, which seriously affects the propagation of seedlings and the development of afforestation.

[0003] Currently, the remaining *Kaloula yunnanensis* species are mainly found in natural forests, with very few plantations. To protect and sustainably utilize this precious tree species and effectively improve the efficiency of resource utilization, it is essential to vigorously develop plantation construction. Therefore, seedlings are the primary issue in afforestation, and to ensure the quantity and quality of seedlings, seed orchards must be established. Grafting is a crucial technical aspect of clonal seed orchards. Clonal seed orchards are widely used because they maintain the superior qualities of superior trees, have clear clonal origins, and flower and bear fruit earlier. Most tree species' seed orchards employ tree management measures such as trunk cutting and dwarfing to facilitate future seed collection and reduce management costs. With the continuous improvement of intensive farming, "orchard-style" management techniques are increasingly being applied, effectively reducing the height of mother trees while increasing production efficiency. One characteristic of grafting propagation is tree dwarfing. Therefore, dwarfing and high-density planting has become an important trend in the development of seed orchards both domestically and internationally. In view of this, this invention provides a method for cultivating dwarf *Kaloula yunnanensis* seedlings through grafting. Summary of the Invention

[0004] To address the difficulties in seedling cultivation and seed collection of *Kaloula yunnanensis*, this invention provides a method for cultivating dwarf *Kaloula yunnanensis* seedlings through grafting. Based on the dwarfing characteristics of the tree after grafting, the optimal time is selected, and the grafting method is used for seedling cultivation, providing technical support for seed orchards of dwarf *Kaloula yunnanensis*.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for grafting and dwarfing seedlings of *Fraxinus chinensis*, comprising the following steps: selecting seedlings of *Fraxinus chinensis* with a ground diameter of 0.5~1.0 cm as rootstock, selecting one-year-old branches of superior *Fraxinus chinensis* as scions, grafting the rootstock and the scions in March, and managing them after grafting.

[0006] Ground diameter (DBD) is a term used in landscaping seedling measurement to indicate the measurement location. DBD refers to the diameter of a tree (sapling) at a certain distance from the ground, similar to trunk diameter (DBD) and breast height (DBH), and is commonly used to indicate the specifications of trees and seedlings. The common understanding is that it refers to "the diameter of the trunk near the ground surface," but in practical applications, it is approximately 5cm above the ground.

[0007] The beneficial effects of this invention are:

[0008] (1) The method of the present invention breaks through the bottleneck of seed or cutting propagation of *Fir chinensis* seedlings, which can achieve a grafting survival rate of over 90%, and the grafting is simple, the cultivation time is short, and the seedlings can be planted in the winter of the same year or the spring of the following year, resulting in significant economic benefits.

[0009] (2) This invention is applicable to grafting of rootstocks with small trunks (0.5~1.0cm in diameter and about 2 years of cultivation of *Cephalotaxus fortunei* seedlings), thereby shortening the cultivation time of *Cephalotaxus fortunei*. Seed gardens built by cultivating clonal seedlings through grafting can bear fruit earlier, dwarf the crown, and facilitate management.

[0010] Based on the above technical solution, the present invention can be further improved as follows.

[0011] Furthermore, in March, the rootstock and the scion were grafted using the cleft grafting method.

[0012] The beneficial effects of adopting the above-mentioned further scheme are: the present invention performs cleft grafting in March (cleft grafting is a type of branch grafting), so the survival rate and growth of *Firx chinensis* are significantly greater than other grafting methods.

[0013] Furthermore, the specific method for cultivating dwarfed seedlings by grafting *Firx chinensis* includes the following steps:

[0014] Step 1, Cultivating Rootstock: In mid-to-late December, collect mature seeds of *Fraxinus chinensis* and sow them in March of the following year. 30±5 days after sowing, transplant the seedlings of *Fraxinus chinensis* (or transplant them into nutrient cups for propagation). Cultivate the transplanted seedlings to obtain *Fraxinus chinensis* seedlings. Select seedlings with a ground diameter of 0.5~1.0 cm as rootstock. The sowing time for rootstock cultivation varies in different regions due to different climatic conditions; the cultivation period varies depending on the quality of management.

[0015] Step 2, collect scions: Select the yellow-branched fir trees with typical traits, good growth, high seed yield and good kernel quality as scion mother trees, and collect one-year-old branches from the scion mother trees as scions. The scions meet the following conditions: obvious bud eyes, plump buds, good maturity, thickness of more than 3 mm and free from diseases and pests.

[0016] Step 3, grafting: In March, the cultivated rootstock and the collected scion are cut and prepared accordingly. Then, the cut rootstock and scion are joined and wrapped in sequence to obtain grafted seedlings. The grafting time varies in different regions due to different climates.

[0017] Step 4, Post-grafting management: Control the relative soil moisture content of the grafted seedlings at 60-80%. Water promptly during droughts to promote callus formation. Observe the growth of buds on the scion of the grafted seedlings 30±5 days after grafting. If the buds on the scion begin to sprout, loosen the binding. Remove all bindings when the buds on the scion grow to 2-3 cm. At the same time, remove any sprouts on the rootstock of the grafted seedlings. Then, manage water, fertilizer, and pest and disease control.

[0018] The method involves loosening the binding without removing the bandage to protect the graft union. If the buds of the scion do not sprout, observation can continue until the buds of the scion sprout before proceeding with the following operations.

[0019] The management of water, fertilizer and pest control refers to the routine management of water, fertilizer and pest control, including management measures such as weeding, proper irrigation and drainage, fertilization and pest control.

[0020] Furthermore, the specific steps for sowing the mature seeds of *Fraxinus chinensis* collected in step 1 are as follows: First, the seeds of *Fraxinus chinensis* are germinated on a sand bed. Then, the germinated seeds are transplanted to a nursery with a light transmittance of 45±5% and cultivated for 30±5 days. After the germination rate of the germinated seeds reaches more than 80%, the seedlings of *Fraxinus chinensis* are transplanted.

[0021] Furthermore, the specific method for cultivating *Cephalotaxus fortunei* seedlings after transplanting the seedlings in step 1 is as follows: Apply topdressing fertilizer once in May of the first year (the current year) after transplanting the seedlings; provide shade in June; apply topdressing fertilizer again in July; apply topdressing fertilizer again in early March of the second year after transplanting the seedlings; remove weak *Cephalotaxus fortunei* seedlings; and then transplant them to separate beds so that the row spacing between adjacent *Cephalotaxus fortunei* seedlings is 20×30 cm.

[0022] Furthermore, in step 2, the scions should be collected before 11:00 AM or after 3:00 PM. For long-distance transportation, protection from pressure, heat, sun, and moisture is necessary, avoiding direct sunlight. Ungrafted scions can be stored for a short period in a cool, low-temperature (5-15℃), high-humidity (relative humidity above 70%) place, covered with plastic film to maintain moisture, for approximately 5 days.

[0023] Furthermore, the grafting in step 3 includes the following specific steps:

[0024] Step 3-1, Scion preparation: Cut the scion into strips 2.0~2.5 cm long and containing at least one single bud. Make a long slant cut from the lower end of the bud of the scion to be grafted, from shallow to deep.

[0025] Step 3-2, Cutting the rootstock: Cut the cultivated rootstock at a distance of 10±3 cm from the ground. Make a vertical cut on the cut surface of the rootstock near the bark layer to obtain a rootstock incision. The depth of the rootstock incision is shorter than the long bevel of the scion to be grafted.

[0026] Step 3-3, Joining and Wrapping: First, insert the long, slanted side of the scion to be grafted into the incision in the rootstock, then tie it tightly at the joint with a strap. The purpose is to align the cambium layers of the scion and the rootstock on one side.

[0027] Furthermore, in step 3-1, the length of the cut surface of the long inclined surface is 1.0~1.5cm, the depth is less than 1 / 3 of the length of the scion to be grafted, the angle between the cut surface of the long inclined surface and the scion to be grafted is 20~30°, the cut surface of the long inclined surface is straight and smooth, and the bottom cross-section of the scion to be grafted on the back side of the long inclined surface is cut into a 45° angled surface.

[0028] Furthermore, the cut surface formed at the cut point of the rootstock 10±3 cm from the ground in step 3-2 is a flat cut surface.

[0029] Furthermore, the strap in step 3-3 is a plastic film, which has a width of 2 cm and a thickness of 20 μm.

[0030] The advantages of adopting the above-mentioned further solution are: the binding tape uses plastic film, and the top plane of the scion and rootstock is sealed and bound with plastic film tape, which eliminates the cumbersome process of sealing with wax in traditional grafting, and the operation is simple. Attached Figure Description

[0031] Figure 1 Diagram of the rootstock prepared for grafting in this invention;

[0032] Figure 2 This is a diagram of the trimmed scion grafted using the cleft grafting method according to the present invention;

[0033] Figure 3 This is a diagram showing the grafting method used in this invention.

[0034] Figure 4 This is a diagram of the grafted bandage of the present invention. Detailed Implementation

[0035] The following description of the principles and features of the present invention, along with the examples given, is for illustrative purposes only and is not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used, unless otherwise specified, are conventional products that can be purchased through legitimate channels.

[0036] Example

[0037] 1. A method for cultivating dwarf seedlings by grafting *Fir chinensis* (yellow-branched fir) according to the present invention.

[0038] This embodiment relates to a method for cultivating dwarf seedlings by grafting *Firx heliotropium indicum*, which includes the following specific steps:

[0039] Step 1, Rootstock cultivation:

[0040] In mid-to-late December, mature cones of *Fraxinus chinensis* were collected. The seeds were threshed, first by composting to remove oil, then spread out to dry and threshed manually with the assistance of manual beating, followed by winnowing to clean the seeds. The seeds were then germinated in a sand bed with a slightly acidic, sandy loam texture. After germination, the seeds were sown in a shaded nursery with 45% light transmittance. Germination began on the 5th day after sowing, and emergence began on the 8th day. The germination rate reached 80% on the 33rd day after sowing, at which point the seedlings were transplanted. The transplanted seedlings were nurtured in the nursery, with fertilizer applied twice a year, in May and July of the same year. Shade was provided in June. In the following spring (early March), diluted human manure was applied. Weak and overly dense seedlings were thinned out, and the seedlings were transplanted to separate beds with a spacing of 20×30cm. After two years of nurturing, *Fraxinus chinensis* with a ground diameter of 0.5-0.8cm were obtained.

[0041] Step 2, Scion Collection:

[0042] Selected yellow-branched fir trees with typical traits, good growth, high seed yield, and good kernel quality were used as scion mother trees. One-year-old branches from the selected scion mother trees were collected as scions. The scions met the following conditions: obvious bud eyes, plump buds, good maturity, a thickness of more than 3 mm, and free from diseases and pests. Specifically, the scions were collected at 9:00 am. Scions that were not grafted on the same day were covered with plastic film and stored in a cool, low-temperature, and high-humidity place.

[0043] Step 3, grafting:

[0044] Grafting should be done in early March, before the rootstock begins to sprout, on sunny days between 8-11 am and 3-6 pm, avoiding the midday heat. A sharp grafting knife is required. The specific steps are as follows:

[0045] (1) Cutting the scion: Remove the leaves from the collected scion, use single bud grafting, and after treatment, form a scion to be grafted. Its length is 2.0~2.5 cm. Cut the scion to be grafted into two cut surfaces, one long and one short. First, cut a long oblique surface from shallow to deep on one side of the lower end of the bud. The cut surface of the long oblique surface is 1.0~1.5 cm long and the depth is 1 / 3 of the length of the scion to be grafted. The angle between the cut surface and the scion is 20~30°. The cut surface should be straight and smooth. Cut a short oblique surface at a 45° angle on one side of the back end, so that the bottom of the scion to be grafted is flat and wedge-shaped.

[0046] (2) Cutting the rootstock: Select a rootstock with a diameter of 0.5cm or more from the ground. Use pruning shears or a hand saw to cut the rootstock about 10cm from the ground. The resulting cut surface is a flat cut surface. Select the side of the rootstock with thick, smooth, and straight bark. Use a knife to make a shallow vertical cut downwards in the bark layer of the cut surface, slightly with the woody part, to form a rootstock incision. The depth of the rootstock incision is slightly shorter than the long oblique surface of the scion.

[0047] (3) Joining and wrapping: First, insert the long oblique surface of the scion to be grafted into the cut of the rootstock, so that the cambium layer of the scion and the rootstock are aligned and aligned, that is, the phloem and the wood are separated; use a 2 cm plastic film as a binding strap to tie the joint formed from top to bottom and the scion tightly, and wrap the exposed wound tightly to obtain the grafted seedling.

[0048] Step 4, Post-grafting management:

[0049] After grafting, soil moisture should be controlled, and watering should be done promptly during dry periods to promote callus formation. Observe the survival rate of the grafted seedlings 30 days after grafting. Once the buds of the scion begin to sprout, the binding can be loosened (loosen the binding but do not remove it completely to protect the graft union). When the new buds on the scion grow to 2-3 cm, all binding can be removed. After successful grafting, any sprouts on the rootstock should be removed promptly. After successful grafting, strengthen water and fertilizer management, including weeding, proper irrigation and drainage, fertilization, and pest and disease control.

[0050] 2. Comparative Example

[0051] (1) Grafting was performed in February before the rootstock sprouted and in April after the rootstock sprouted as controls. Otherwise, the grafting method was the same as described above.

[0052] (2) A comparative grafting experiment was conducted using the cleft grafting method and the bark grafting method. Otherwise, the grafting methods were the same as those described above.

[0053] 3. Survival rate and growth measurement

[0054] At the end of December of the grafting year, the number of surviving plants was counted, and the growth of new shoots sprouting from the scion was measured, including length and thickness. The length of the new shoots was measured using a steel tape measure, from the graft union to the tip of the shoot. The thickness of the new shoots was measured using vernier calipers, at a point 1 cm from the base of the new shoot to the graft union.

[0055] Table 1 shows the grafting survival rate and growth of *Firx negundo* var. *mongolica* grafted at different times in March using the cleft grafting method of this invention, the whip grafting method in the control example, and the bark grafting method.

[0056] Table 1 Comparison of grafting survival rate and growth at different times using cleft grafting, whip grafting, and bark grafting methods.

[0057]

[0058] As can be seen from Table 1, the grafting method of the present invention achieves a better survival rate and better growth condition than other grafting methods, regardless of the time or grafting method.

[0059] In summary, the grafting method of this invention breaks through the bottleneck of seed or cutting propagation of *Kaloula yunnanensis*, enabling a grafting survival rate of over 90%, and shortening the cultivation time. The seedlings can be transplanted for afforestation in the winter of the same year or the spring of the following year. This solves the problems of slow seed propagation and low quantity of *Kaloula yunnanensis*, and provides a scientific reference for the construction of dwarf clonal seed orchards of *Kaloula yunnanensis*.

[0060] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction.

[0061] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for cultivating dwarf seedlings by grafting *Firx chinensis*, characterized in that, The process includes the following steps: selecting seedlings of *Cephalotaxus fortunei* with a ground diameter of 0.5-1.0 cm as rootstock, selecting one-year-old branches of superior *Cephalotaxus fortunei* as scions, grafting the rootstock and scions in March, and managing them after grafting. In March, the rootstock and the scion were grafted using the cleft grafting method. The method for grafting and dwarfing seedlings of *Fircus syriacus* includes the following steps: Step 1, Cultivating rootstock: In mid-to-late December, collect mature seeds of *Cephalotaxus fortunei* and sow them in March of the following year. 30±5 days after sowing, transplant the seedlings of *Cephalotaxus fortunei*. Cultivate the transplanted seedlings to obtain *Cephalotaxus fortunei* seedlings. Select the seedlings of *Cephalotaxus fortunei* with a ground diameter of 0.5~1.0 cm as rootstock. Step 2, collect scions: Select the yellow-branched fir trees with typical traits, good growth, high seed yield and good kernel quality as scion mother trees, and collect one-year-old branches from the scion mother trees as scions. The scions meet the following conditions: obvious bud eyes, plump buds, good maturity, thickness of more than 3 mm and free from diseases and pests. Step 3, grafting: In March, the cultivated rootstock and the collected scion are cut and treated accordingly. Then, the cut rootstock and scion are joined and wrapped in sequence to obtain grafted seedlings. Step 4, Post-grafting management: Control the relative soil moisture content of the grafted seedlings at 60-80%. Observe the growth of buds on the scion of the grafted seedlings 30±5 days after grafting. If the buds on the scion sprout, loosen the binding. When the buds on the scion grow to 2-3 cm, remove all binding. At the same time, remove any sprouts on the rootstock of the grafted seedlings. Then, manage water, fertilizer, and pest and disease control.

2. The method for cultivating dwarf seedlings by grafting *Firx chinensis* according to claim 1, characterized in that, The specific steps for sowing the mature seeds of *Fraxinus chinensis* collected in step 1 are as follows: First, the seeds of *Fraxinus chinensis* are germinated on a sand bed. Then, the germinated seeds are transplanted to a nursery with a light transmittance of 45±5% and cultivated for 30±5 days. After the germination rate of the germinated seeds reaches more than 80%, the seedlings of *Fraxinus chinensis* are transplanted.

3. The method for cultivating dwarf seedlings by grafting *Firx chinensis* according to claim 1 or 2, characterized in that, The specific method for cultivating *Cephalotaxus fortunei* seedlings after transplanting the seedlings in step 1 is as follows: Apply topdressing fertilizer once in May of the first year after transplanting the seedlings; provide shade in June; apply topdressing fertilizer again in July; apply topdressing fertilizer again in early March of the second year after transplanting the seedlings; remove weak seedlings; and then transplant them to separate beds so that the row spacing between adjacent seedlings is 20×30 cm.

4. The method for cultivating dwarf seedlings by grafting *Firx chinensis* according to claim 2, characterized in that, In step 2, the scions are collected before 11 a.m. or after 3 p.m.

5. The method for cultivating dwarf seedlings by grafting *Firx chinensis* according to claim 2, characterized in that, Step 3, grafting, includes the following specific steps: Step 3-1, Scion preparation: Cut the scion into strips 2.0~2.5 cm long and containing at least one single bud. Make a long slant cut from the lower end of the bud of the scion to be grafted, from shallow to deep. Step 3-2, Cutting the rootstock: Cut the cultivated rootstock at a distance of 10±3 cm from the ground. Make a vertical cut on the cut surface of the rootstock near the bark layer to obtain a rootstock incision. The depth of the rootstock incision is shorter than the long bevel of the scion to be grafted. Step 3-3, Joining and wrapping: First, insert the long oblique side of the scion to be grafted into the incision of the rootstock, and then tie it tightly with a strap at the joint. No bagging is required.

6. The method for cultivating dwarf seedlings by grafting *Firx chinensis* according to claim 5, characterized in that, In step 3-1, the length of the cut surface of the long inclined surface is 1.0~1.5cm, the depth is less than 1 / 3 of the length of the scion to be grafted, the angle between the cut surface of the long inclined surface and the scion to be grafted is 20~30°, the cut surface of the long inclined surface is straight and smooth, and the bottom cross-section of the scion to be grafted on the back side of the long inclined surface is cut into a 45° angled surface.

7. The method for cultivating dwarf seedlings by grafting *Firx chinensis* according to claim 5, characterized in that, The cut surface formed at the cut point of the rootstock 10±3 cm from the ground in step 3-2 is a flat cut surface.

8. The method for cultivating dwarf seedlings by grafting *Firx chinensis* according to claim 5, characterized in that, The straps in step 3-3 are made of plastic film, which has a width of 2 cm and a thickness of 20 μm.

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