Liquidambar formosana hance improved variety breeding method based on liquidambar formosana hance leaf color evaluation

Abstract

The invention discloses a liquidambar formosana hance improved variety breeding method based on liquidambar formosana hance leaf color evaluation, which comprises the following steps: collecting liquidambar formosana hance seeds of different families, breeding to obtain nursery stocks, using the nursery stocks to build a test forest, and after the test forest is built, determining the test forest in the vigorous leaf color change period of the liquidambar formosana hance in December every year; the measured indexes comprise a leaf color index and a growth index; the leaf color indexes comprise a leaf color system, a single plant color change amount and leaf CIE-Lab color space parameters; the growth indexes comprise the preservation rate and the leaf health degree; the method comprises the following steps: selecting sweetgum family varieties reaching various indexes as a finally bred excellent discoloring family, and then cultivating and building a sweetgum forest according to the contents of seed propagation, seedling cultivation, afforestation and soil preparation, field planting, tending, topdressing, forest land management and the like in building a test forest. The method can be used for breeding the liquidambar formosana hance excellent discoloring family, and has the advantages of convenience, effectiveness and suitability for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of liquidambar breeding, and particularly relates to a liquidambar improved variety breeding method based on leaf color evaluation of colorful liquidambar. Background Art

[0002] Liquidambar formosana Liquidambar formosana Hance is a species of Liquidambar formosana in the Hamamelidaceae family. Liquidambar ) is a deciduous tree with a wide distribution. Liquidambar has a wide adaptability, strong wind and fire resistance, and is naturally easy to regenerate. It is suitable for growing on red and yellow soils and is known as a pioneer tree species for barren mountains and rocky mountains. After autumn, its leaves gradually change from green to red, purple, orange and other colors. It is known as "maple leaves are redder than February flowers". It has great ornamental value and is an excellent forest landscape tree species. It plays an important role in cultivating colorful forests, effectively improving the landscape value and tourism value of forests, and promoting the development of forest tourism. Through scientific breeding, the excellent Liquidambar family selected is not only highly adaptable and healthy, but also has bright leaves and good ornamental effects, which can greatly exert the ornamental value of Liquidambar. When breeding varieties with good color-changing effects, it is necessary to study and evaluate the genetic variation among Liquidambar families, and use full-length transcriptome sequencing technology to deeply understand the genetic basis of the color-changing period of Liquidambar leaves, obtain the genetic factors that affect leaf color change, and then use them as a basis for breeding of improved varieties. However, the research on the genetic factors of leaf color change is difficult, and there are many varieties of Liquidambar, so the research workload is large. It is still necessary to study convenient and effective Liquidambar variety breeding methods that are suitable for promotion and application. Summary of the invention

[0003] In view of the above shortcomings, the present invention discloses a method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored Liquidambar formosana, which can not only breed improved color-changing families of Liquidambar formosana, but also has the advantages of being convenient, effective and suitable for promotion and application.

[0004] The present invention is achieved by adopting the following technical solutions: A method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored-leaf Liquidambar formosana comprises the following steps: S1. Collect liquidambar seeds from different families and propagate them to obtain seedlings with a height greater than 40 cm; S2. Using the seedlings described in step S1 to construct a test forest, which specifically includes the following contents: The afforestation experiment was divided into more than 3 test sites; in the test sites, each family planted 15 plants, and a single row of 5 plants formed a plot; the afforestation density was 110 plants / mu, and the spacing between plants and rows was 2m×3m; the afforestation was carried out from January to April of the same year, and the specifications of the planting holes were 60cm wide, 40cm wide, and 40cm deep. 500g of compound fertilizer was applied in each planting hole before planting; the survival rate was investigated one month after afforestation, and replanting was carried out; pesticides were sprayed in April every year for pest control, and compound fertilizer was applied at a rate of 500g / plant from May to June every year, and the soil was loosened and weeded once from July to August every year; S3. After the experimental forest is established, the experimental forest shall be measured in December every year when the leaves of Liquidambar formosana are at their peak of color change, that is, when more than 70% of the plants with completely changed leaves account for more than 80% of the total plants; The measured indicators include leaf color indicators and growth indicators; the leaf color indicators include leaf color system, color change amount of a single plant, and leaf CIE-Lab color space parameters (lightness L, red-green attribute a, yellow-blue attribute b); The leaf color is divided into red, yellow, orange and green. The leaf color of each Liquidambar formosana is determined by visual observation using a color comparison card. If at least three plants of a family have the same color in each plot for three consecutive years, the Liquidambar formosana of the family is marked as a qualified variety, and all qualified varieties are grouped into a set A1. The single plant color change amount is the percentage of the number of color-changed leaves of each Liquidambar formosana plant to the total number of leaves. If the single plant color change amount of at least 3 plants in a family in each plot is greater than or equal to 70%, the Liquidambar formosana of the family is marked as a qualified variety, and all qualified varieties are grouped into set A2; The leaf CIE-Lab color space parameters are as follows: in each plot, plants with a color change amount greater than or equal to 70% are selected, 3 to 6 leaves are collected, and then 3 leaves are randomly selected to wipe the surface dust and the leaf color parameters are measured using a colorimeter. During the measurement, the front color of the leaf is measured using a window with a diameter of 8 mm under a D65 light source and an angle of 10°. Ten positions of each leaf are measured and the average value is calculated; the leaf color parameters include the lightness L value (the larger the L, the brighter the leaf color), the red-green attribute a value (the larger the a, the more the leaf color tends to red), and the yellow-blue attribute b value (the larger the b, the more the leaf color tends to yellow); Taking positive green and positive red as the standard, the lightness L value, red-green attribute a value, and yellow-blue attribute b value of the leaf color parameters are converted into standardized scores, and positive green is assigned 0 points and positive red is assigned 100 points. According to the L, a, and b values ​​of positive green and positive red, the color difference ΔE between the two is calculated according to the color difference calculation formula 0 , to collect leaves L i 、a i 、b i Value and positive red L 红 、a红 、b 红 Calculate the color difference ΔE 1 , and finally by calculating ΔE 1 With ΔE 0 The color standardized score S of the collected leaves is calculated by the ratio of 红 =41.07, a 红 =37.84, b 红 =24.17 and L 绿 =28.69, a 绿 =1.47, b 绿 =-1.55, the specific calculation formula is as follows: Δ E 0 =[(Δ L ) 2 +(Δ a ) 2 +(Δ b ) 2 ] 0.5 ; Δ L = L 红 - L 绿 ; Δ a = a 红 - a 绿 ; Δ b = b 红 - b 绿 ; ΔE 1 = [(Δ L i ) 2 +(Δ a i ) 2 +(Δ b i ) 2 ] 0.5 ; Δ L i = L 红 - L i ; Δ a i = a 红 - a i ; Δ b i = b 红 - bi ; S =100-(ΔE 1 / Δ E 0 ) × 100; If the color selection standardized score S of at least 3 plants in each plot of each test site in a family is greater than or equal to 60 within 3 years, the family will be subjected to nested design variance analysis with year, test site, plot, and plant as independent variables and score as dependent variable. If the effects of year, test site, plot, and plant on the score are not significantly different, the Liquidambar variety of the family will be marked as a qualified variety, and all qualified varieties will be grouped into set B1; The growth indicators include preservation rate and leaf health; The preservation rate is the number of surviving plants in a single row of 5 plants in each plot. If the preservation rate of a family in each plot is greater than or equal to 3, the Liquidambar variety of the family is marked as a qualified variety, and all qualified varieties are grouped into set A3; The leaf health degree is obtained by scanning the collected leaves with a scanner, and then importing the scanned images into a plant image analyzer to count the areas of leaf spots, insect damage, and rot, and calculating the percentage of the sum of the areas of spots, insect damage, and rot to the total leaf area. If the leaf health degree of at least 3 plants of a family in each plot is below 10%, the liquidambar variety of the family is marked as a qualified variety, and all qualified varieties are grouped into a set B2; S4. Select the intersection of set A1, set A2 and set A3 to form set A, select the intersection of set B1 and set B2 to form set B, and then use the intersection of set A and set B as the final selected excellent color-changing family to cultivate and build a liquidambar forest according to steps S1 and S2.

[0005] Furthermore, in step S1, seeds are collected from individual Liquidambar formosana plants in October or November, and then in January or February of the following year, the seeds are soaked in water for 48 hours, and then disinfected with 0.2% potassium permanganate and spread on a sand bed for germination. Watering is performed regularly every day to keep the sand bed moist. 30 to 40 days after sowing and when the seedlings grow to 1 to 2 cm, the seedlings are taken out and their roots are cut, with the main root length retained at 2 to 4 cm. The seedlings are then transplanted into a non-woven bag filled with a substrate, and then placed in a seedbed for cultivation.

[0006] Furthermore, the seedlings are transplanted and placed in non-woven bags filled with substrate, and then placed in a seedbed for cultivation, using a shade net with a light transmittance of 40% to 50% for shading; from May to September of the same year, foliar fertilizer is applied twice a month, and foliar fertilizer is stopped after October; in the rainy season when the temperature is above 25°C, a 0.1% thiophanate-methyl aqueous solution or a 0.4% carbendazim aqueous solution is sprayed once every 15 days (to prevent the occurrence of diseases such as damping-off, sudden wilt, and root rot). If snails are found, 6% metaldehyde carbaryl granules are used for prevention and control.

[0007] Furthermore, the matrix includes the following components in parts by weight: 35-45 parts of humus soil, 40-50 parts of decomposed coconut bran, 4-6 parts of fermented mushroom residue, and 8-15 parts of perlite; the foliar fertilizer includes the following components in mass fractions: 0.3-0.5% of compound fertilizer, 0.1% of nitrogen fertilizer, and the balance is water. By preparing a matrix and foliar fertilizer suitable for the growth of Liquidambar formosana, the nutrients required for the growth of Liquidambar formosana are increased.

[0008] Furthermore, the N:P 2 O 5 :K 2 O is 15:15:15; and the nitrogen fertilizer is urea.

[0009] Furthermore, in step S2, the soil is loosened and weeded once in July and August every year, specifically, the weeds and shrubs that affect the growth of trees in the forest are cut down, and the soil is loosened within a range of 50 cm to the left and right, 60 cm above, 40 cm below, and 20 cm deep, centered on the plant.

[0010] Furthermore, in step S3, the color change amount of a single plant is the percentage of the number of colored leaves of each Liquidambar formosana plant to the total number of leaves, and the color change amount of a single plant is set to 11 gradients, with each 10% being a gradient. The color change amount of a single plant when all leaves have not changed color (i.e., are green) is 0%, and the color change amount of a single plant when all leaves have changed color is 100%.

[0011] Compared with the prior art, this technical solution has the following beneficial effects: 1. The method of the present invention complies with the relevant requirements of the industry standard "Guidelines for Specificity, Consistency and Stability Testing of New Plant Varieties - Liquidambar formosana" (LY / T 3207-2020) and the Guangxi local standard "Technical Specifications for Approval of Ornamental Plant Varieties" (DB 45 / T 1781-2018). Through scientific breeding (including regional trials, reproduction and cultivation, experimental forest determination, selection and evaluation of leaf color indicators and growth indicators, etc.), the excellent Liquidambar formosana families screened out are not only highly adaptable and healthy in growth, but also have bright leaf color and good ornamental effect, which can greatly exert the ornamental value of Liquidambar formosana.

[0012] 2. The evaluation of different Liquidambar families in the test forest by the present invention includes leaf color index and growth index, wherein the leaf color index is composed of leaf color system, single plant color change amount and leaf CIE-Lab color space parameter, and the growth index is composed of preservation rate and leaf health. By measuring and analyzing the leaf color index, not only can the Liquidambar families with good color change stability be effectively evaluated and screened out, but also each family is scored according to the leaf CIE-Lab color space parameter and the family with a score of not less than 60 points is screened out, which can effectively screen out excellent Liquidambar families with good Liquidambar leaf color specificity (red and bright leaves) and good ornamental effect; at the same time, combined with the growth index, Liquidambar families with strong adaptability and healthy growth can be screened out, thereby obtaining excellent Liquidambar families with strong adaptability, healthy growth and good color change effect, which are suitable for promotion and application in cultivating colored forests, and effectively improving the landscape value and tourism value of forests. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a measurement position diagram selected on the leaf when measuring the leaf color parameters in step S33 in Example 1.

[0014] Figure 2 This is the color information result diagram of each score node in the final score library in step S37 in Example 1.

[0015] Figure 3 It is a single-plant picture of Liquidambar formosana with a score of 70 when the leaf CIE-Lab color space parameter is measured in step S37 in Example 1.

[0016] Figure 4 It is a single-plant picture of Liquidambar formosana with a score of 60 when the leaf CIE-Lab color space parameter is measured in step S37 in Example 1.

[0017] Figure 5 It is a single-plant picture of Liquidambar formosana with a score of 50 when the leaf CIE-Lab color space parameter is measured in step S37 in Example 1.

[0018] Figure 6 This is a picture of Liquidambar formosana family No. 11 after cultivation in Example 1.

[0019] Figure 7 This is a picture of Liquidambar formosana family No. 78 after cultivation in Example 1.

[0020] Figure 8 This is a picture of Liquidambar formosana family No. 100 after cultivation in Example 1.

[0021] Fig. 9 This is a picture of Liquidambar formosana family No. 142 after cultivation in Example 1.

[0022] Fig.10 This is a picture of Liquidambar formosana family No. 237 after cultivation in Example 1. DETAILED DESCRIPTION

[0023] The present invention is further described by the following examples, but is not intended to be limiting of the present invention. Specific experimental conditions and methods not specified in the following examples are conventional methods commonly known to those skilled in the art.

[0024] Example 1: Referring to the method for selecting improved varieties of Liquidambar formosana based on leaf color evaluation of colored Liquidambar formosana described in the present invention, the selection of excellent Liquidambar formosana lines was carried out, and the specific process was as follows: S1. In 2017, with the support of the Guangxi Zhuang Autonomous Region's special forestry seed project "Conservation and Utilization of Guangxi Native Colored Leaf Tree Seed Plasma Resources", 11 Liquidambar seed sources and 233 families were collected in Guangxi Zhuang Autonomous Region and Guizhou Province. In January 2018, they were sown in the self-built nursery of the Guangxi Zhuang Autonomous Region Forestry Science Research Institute (Nanning, Guangxi), and more than 70,000 high-quality seedlings were cultivated, and a total of 136 families were obtained that could be used for the design of seedlings for the experimental forest; The reproduction process includes the following: S11. Collect Liquidambar seeds from October to November and place them in the sun to dry. Remove impurities after the seeds are removed, collect pure seeds, and store them in a refrigerator at 4°C for later use; S12. In January or February of the following year, soak the seeds in water for 48 hours, disinfect them with 0.2% potassium permanganate, and then spread them on a sand bed for germination. Water them regularly every day to keep the sand bed moist. Transplant the seedlings when they are 1 cm to 2 cm long 30 to 40 days after sowing. S13, using a tool to loosen the sand and take out the sprouts, cut off the long taproot, and keep the taproot length at 2cm to 4cm; using a tool to insert a small hole in the middle of the nutrient bag, preferably with a depth of 4cm to 6cm, vertically put the sprouts in, gently compact the matrix from the side, and irrigate with enough water to fix the roots; the matrix includes the following components in parts by weight: 40 parts of humus soil, 45 parts of decomposed coconut bran, 5 parts of fermented mushroom residue, and 10 parts of perlite, and 0.1% of the total weight of the matrix can also be added to the matrix. Composite microbial agent; S14. After the transplanted seedlings are placed in the seedbed, shade nets with a light transmittance of 40% to 50% are used for timely shading, and the shade nets are removed after October. During the rapid growth period of the seedlings, water them in time according to the moisture status of the substrate, and water them in time after topdressing. Watering needs to be even and thorough. From May to September, foliar fertilizer is applied twice a month, and fertilization is stopped after October. The principle of weeding is "early weeding, small weeding, and weeding without weeding". Manual weeding is used to avoid weeding and root damage. In the rainy season when the temperature is above 25°C, spray once every 15 days with a 0.1% thiophanate-methyl aqueous solution or a 0.4% carbendazim aqueous solution to prevent the occurrence of diseases such as damping-off, damping-off, and root rot. If snails and other pests are found, use snail killer (6% tetraacetaldehyde carbaryl) granules for prevention and control. The foliar fertilizer includes the following components by mass fraction: 0.3-0.5% compound fertilizer, 0.1% nitrogen fertilizer, and the balance is water. The N:P ratio of the compound fertilizer is 2.5:1. 2 O 5 :K 2 O is 15:15:15; and the nitrogen fertilizer is urea.

[0025] S2. Select high-quality seedlings with a height of >40 cm to establish a test forest, which specifically includes the following: S21. A total of three test sites were designed, each of which adopted a completely randomized block design; each of the three test sites had 136 families; the test forest location and its climate and soil conditions were as follows: Nanning test site: Located in the Dongsheng branch of Gaofeng State Forest Farm in the northern suburbs of Nanning (E 108.407515°, N22.981340°), 130 m above sea level, it has a southern subtropical monsoon climate, with an average annual temperature of 21.6 °C and an annual rainfall of 1350 mm; the soil is mainly yellow-red soil, with a soil layer thickness of more than 1.0 m; Liuzhou test site: Located in Bozhai Branch of Huangmian State Forest Farm, Luzhai County, Liuzhou City (E 109.884329°, N22.780638°), 200 m above sea level, with a subtropical monsoon climate, an average annual temperature of 19.0 ℃, and an annual rainfall of 1750 mm; the soil is mainly yellow-red soil, with a soil layer thickness of more than 1.0 m; Hezhou test site: Located at Liupai Branch of Daguishan State Forest Farm, Babu District, Hezhou City (E 111.730266°, N24.7174602°), 150 m above sea level, with a subtropical monsoon climate, an average annual temperature of 21.2 °C, and an annual rainfall of 1940 mm; the soil is mainly yellow-red soil, with a soil layer thickness of 0.8-1.0 m; S22. In each test site, each family planted 15 plants, and 5 plants were arranged in a single row; the afforestation density was 110 plants / mu, and the row spacing was 2m×3m; the three test sites were all machine-cultivated and land was prepared, and holes were dug manually for planting, with specifications of 60cm (hole width) × 40cm (hole bottom width) × 40cm (hole depth), and 500g of compound fertilizer was placed in each hole before planting; S23. Complete the afforestation from January to April 2019, investigate the survival rate one month after afforestation, and carry out replanting. Complete the soil loosening and weeding once from July to mid-August; apply 500g of compound fertilizer per plant from May to June 2020, and carry out soil loosening, weeding and tending in combination with fertilization; spray pesticides in April 2021, carry out disease and insect pest control, and apply 500g of compound fertilizer per plant from May to June, and weed and tend; spray pesticides in April 2022, carry out disease and insect pest control, and apply 500g of compound fertilizer per plant from May to June, and weed and tend; spray pesticides in May 2023, carry out disease and insect pest control, and weed and tend in June.

[0026] S3. After the experimental forest is established, the experimental forest shall be measured in December every year when the leaves of Liquidambar formosana in the experimental forest are at their peak of color change, that is, when more than 70% of the plants with completely changed leaves account for more than 80% of the total plants; the measured indicators include leaf color indicators and growth indicators; the leaf color indicators include leaf color system, color change amount of a single plant, and leaf CIE-Lab color space parameters (lightness L, red-green attribute a, yellow-blue attribute b); the growth indicators include preservation rate and leaf health; The test forest was measured in December 2019, mainly to determine the appropriate measurement period and breeding standards for Liquidambar formosana plants. Therefore, the measurement data will not be used in breeding analysis. Then, the Liquidambar formosana test forests at three test sites were measured for three consecutive years in 2020, 2021, and 2022. The specific measurement indicators, measurement steps, and requirements are as follows: S31. Leaf color: The leaf color is divided into red, yellow, orange and green. The leaf color of each Liquidambar formosana plant is determined by visual observation using a color comparison card; S32, single plant color change amount: the single plant color change amount is the percentage of the number of color-changed leaves of each Liquidambar formosana plant to the total number of leaves, and the single plant color change amount is set to 11 gradients, with each 10% being a gradient. The single plant color change amount when all leaves do not change color (i.e., green) is 0%, and the single plant color change amount when all leaves change color is 100%; if the single plant color change amount is between 50% and 70%, three people are required to observe and count to determine the color change amount; S33. Leaf CIE-Lab color space parameters: In terms of color expression range, the Lab mode is the most comprehensive among the current color expression modes. It defines the most colors and is independent of light and equipment. It is a color system based on physiological characteristics. Therefore, the selection of the CIE-Lab color space can accurately and objectively quantify the color of liquidambar formosana leaves. The CIE-Lab color space parameters of the leaves are obtained by selecting plants with a color change amount greater than or equal to 70% in each plot, collecting 3 to 6 leaves, and then randomly selecting 3 leaves to wipe the surface dust and use a colorimeter (Hangzhou Color Spectrum Spectrophotometer CS-650) to measure the leaf color parameters. During the measurement, the front color of the leaves is measured under a D65 light source and an angle of 10° using an 8 mm diameter window. Each leaf is measured at 10 locations (such as Figure 1 ) and calculate the average value; the leaf color parameters include lightness L value (the larger L is, the brighter the leaf color is), red-green attribute a value (the larger a is, the more red the leaf color is), and yellow-blue attribute b value (the larger b is, the more yellow the leaf color is); S34, survival rate: the survival rate is the number of surviving plants in a single row of 5 plants in each plot; S35. Leaf health: The leaf health is determined by scanning the collected leaves with a scanner, and then importing the scanned images into a plant image analyzer (Wanshen LA-S series plant image analyzer) to count the areas of leaf lesions, insect damage, and rot, and calculating the percentage of the total area of ​​lesions, insect damage, and rot to the total leaf area to obtain the leaf health.

[0027] According to the above determination criteria, the selection of excellent Liquidambar formosana family varieties is as follows: S36. Evaluate the growth adaptability of individual plants based on the preservation rate in 2022. If the preservation rate of a family in each plot is greater than or equal to 3, it means that the adaptability of the family is good, and the Liquidambar varieties of the family are marked as qualified varieties, and all qualified varieties are grouped into set A3; screen the data of the color change measurement of individual plants. If at least 3 plants of a family in each plot have a color change amount greater than or equal to 70%, the Liquidambar varieties of the family are marked as qualified varieties, and all qualified varieties are grouped into set A2; at the same time, if at least 3 plants of a family in each plot have the same color for 3 consecutive years (2020, 2021, and 2022), the Liquidambar varieties of the family are marked as qualified varieties, and all qualified varieties are grouped into set A1; S37. After three years of testing, the color system of Liquidambar formosana leaves is green, red, yellow, and orange. Yellow and orange are both a mixture of green and red, and are between green and red in the international color library. Taking positive green and positive red as the standard, the lightness L value, red-green attribute a value, and yellow-blue attribute b value of the leaf color parameters are converted into standardized scores, and positive green is assigned 0 points and positive red is assigned 100 points. According to the L, a, and b values ​​of positive green and positive red, the color difference ΔE between the two is calculated according to the color difference calculation formula 0 , to collect leaves L i 、a i , b i Value and positive red L 红 、a 红 , b 红 Calculate the color difference ΔE 1 , and finally by calculating ΔE 1 With ΔE 0 The color standardized score S of the collected leaves is calculated by the ratio of L is determined by the positive green and positive red parameters in the international color library. 红 =54, a 红 =81, b 红 =70 and L 绿 =88, a 绿 =-79, b 绿 =81, the specific calculation formula is as follows: Δ E 0 =[(Δ L ) 2 +(Δ a ) 2 +(Δ b ) 2 ] 0.5 =[(-34) 2 +(160) 2 +(-11) 2 ] 0.5 =163.94 Δ L = L 红 - L 绿 =54-88; Δ a = a 红 - a 绿 =81-(-79); Δ b = b 红 - b 绿 =70-81 ΔE 1 = [(Δ L i ) 2 +(Δ ai ) 2 +(Δ b i ) 2 ] 0.5 Δ L i = L 红 - L i =54- L i ; Δ a i = a 红 - a i =81- a i ; Δ b i = b 红 - b i =70- b i S =100-(ΔE 1 / Δ E 0 ) × 100 = 100 - (ΔE 1 / 163.94) ×100; The standardized color scores of all collected leaves were calculated according to the above formula to obtain the standardized color score library of Liquidambar leaf. However, since both positive green and positive red are one of the three primary colors, they are difficult to achieve in nature. Therefore, for the sake of comparison, the highest score (60.80, L=41.07, a=37.84, b=24.17) and the lowest score (32.94, L=28.69, a=1.47, b=-1.55) were selected in the standardized color score library of Liquidambar leaf to replace positive red and positive green, respectively. The scores of the collected leaf colors were recalculated according to the above formula to obtain the final score library, which was ranked. The colors of each score node are shown in Tables 1 and Figure 2 , the photos of Liquidambar formosana corresponding to some of the scores are shown below Figures 3 to 5 As shown; Table 1 Color information of each score node in the final score library

[0028] Referring to the industry standard "Guidelines for Specificity, Consistency and Stability Testing of New Plant Varieties", the specificity of traits is evaluated by difference constancy, that is, the difference between the test material and similar varieties is very clear; from Table 1 and Figures 2 to 5It can be seen that the leaves with a final score ≥60 are redder and brighter than those with a score below 50, and have better ornamental effects. Therefore, the leaf color ≥60 is regarded as liquidambar formosana leaf color specificity. The scores and analysis of some families are shown in Tables 2 and 3 (Y represents year, S represents site, R represents region, and I represents individual. I(R(S(Y))) means that I is nested in R, R is nested in S, and S is nested in Y); Table 2 Leaf color scores of some families at each test point in three years

[0029] Table 3 Analysis of variance of nested design of some families

[0030] After ranking the scores of leaves collected in each plot, the final score ≥ 60 was screened out. Then, year, test site, plot, and individual plant were used as independent variables, and the final score was used as the dependent variable. Multifactor variance analysis was performed on each screened family. If the year, test site, plot, and individual plant had no significant effect on the score of the family number, it met the principles of stability and consistency and was further selected to form the selected subset B1; S38. If the leaf health of at least three plants of a family in each plot is below 10%, the Liquidambar varieties of the family are marked as qualified varieties, and all qualified varieties are grouped into set B2; S4. By analyzing the growth data of the Liquidambar experimental forests at the three test sites measured in 2022 and the three-year single-plant color change data, the intersection of set A1, set A2 and set A3 were selected to form set A, which includes 8 families, No. 11, No. 78, No. 87, No. 100, No. 105, No. 142, No. 228, and No. 237; the intersection of set B1 and set B2 were selected to form set B, which includes 5 families, No. 11, No. 78, No. 100, No. 142, and No. 237; the intersection of set A and set B was used as the final selected excellent color-changing families, which are Liquidambar varieties of 5 families, No. 11, No. 78, No. 100, No. 142, and No. 237. The cultivation pictures of the experimental forests of the 5 families can be found in Figures 6 to 10 ; S5. Take Liquidambar varieties of 5 families, namely, No. 11, No. 78, No. 100, No. 142 and No. 237, for cultivation. The cultivation and afforestation process includes the following: S51. Land preparation for afforestation: The planting method is open-pit planting, with a row spacing of 2m×3m and a sill density of 110 plants / mu; sill specifications: bottom length 30cm×bottom width 30cm×sill depth 30cm; 0.5 kg / plant of organic-inorganic compound fertilizer is applied as base fertilizer per sill; S52. Planting: Choose an environment with sufficient rainfall and moist soil for afforestation. Complete the preservation rate survey within 30 days after planting and carry out appropriate replanting. S53. Tending: Tending is done once every July to August. Grass cutting and ridge expansion are carried out to remove weeds and shrubs that affect the growth of trees in the forest. The soil is loosened 20 cm deep, 50 cm to the left and right, 60 cm above, 40 cm below, and 20 cm in depth, with the plant as the center. S54. Topdressing: Topdress once every May to July for three consecutive years. Dig a fertilizer ditch at a suitable location away from the tree roots, and evenly apply 0.15 to 0.25 kg of fertilizer in the ditch. The fertilizer type is mainly compound fertilizer. After fertilization, cover the soil as required to prevent fertilizer loss; S55. Forest management: Safety training for construction personnel, construction training, distribution of safety drugs, promotional slogans, banners, etc.; collect relevant information and do a good job of archiving. At the same time, do a good job of forest fire prevention, pest prevention, and human damage prevention.

[0031] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored liquidambar formosana, characterized in that: The following steps are involved: S1. Collect liquidambar seeds from different families and propagate them to obtain seedlings with a height greater than 40 cm; S2. Using the seedlings described in step S1 to construct a test forest, which specifically includes the following contents: The afforestation experiment was divided into more than 3 test sites; in the test sites, each family planted 15 plants, and a single row of 5 plants formed a plot; the afforestation density was 110 plants / mu, and the spacing between plants and rows was 2m×3m; the afforestation was carried out from January to April of the same year, and the specifications of the planting holes were 60cm wide, 40cm wide, and 40cm deep. 500g of compound fertilizer was applied in each planting hole before planting; the survival rate was investigated one month after afforestation, and replanting was carried out; pesticides were sprayed in April every year for pest control, and compound fertilizer was applied at a rate of 500g / plant from May to June every year, and the soil was loosened and weeded once from July to August every year; S3. After the experimental forest is established, the experimental forest shall be measured in December every year when the leaves of Liquidambar formosana are at their peak of color change, that is, when more than 70% of the plants with completely changed leaves account for more than 80% of the total plants; The measured indicators include leaf color indicators and growth indicators; the leaf color indicators include leaf color system, single plant color change amount, and leaf CIE-Lab color space parameters; The leaf color is divided into red, yellow, orange and green. The leaf color of each Liquidambar formosana is determined by visual observation using a color comparison card. If at least three plants of a family have the same color in each plot for three consecutive years, the Liquidambar formosana of the family is marked as a qualified variety, and all qualified varieties are grouped into a set A1. The single plant color change amount is the percentage of the number of color-changed leaves of each Liquidambar formosana plant to the total number of leaves. If the single plant color change amount of at least 3 plants in a family in each plot is greater than or equal to 70%, the Liquidambar formosana of the family is marked as a qualified variety, and all qualified varieties are grouped into set A2; The leaf CIE-Lab color space parameters are as follows: in each plot, plants with a color change amount greater than or equal to 70% are selected, 3 to 6 leaves are collected, and then 3 leaves are randomly selected to wipe the surface dust and the leaf color parameters are measured using a colorimeter. During the measurement, the front color of the leaf is measured under a D65 light source and an angle of 10° using an 8 mm diameter window. Ten positions of each leaf are measured and the average value is calculated; the leaf color parameters include lightness L value, red-green attribute a value, and yellow-blue attribute b value; Taking true green and true red as the standard, the lightness L value, red-green attribute a value, and yellow-blue attribute b value of the leaf color parameters were converted into standardized scores, with true green being assigned 0 points and true red being assigned 100 points. According to the L, a, and b values ​​of true green and true red, the color difference ΔE0 between the two was calculated according to the color difference calculation formula to collect leaf L i 、a i 、b i Value and positive red L 红 、a 红 、b 红 The color difference ΔE1 is calculated, and finally the color standardization score S of the collected leaves is calculated by calculating the ratio of ΔE1 to ΔE0, where L 红 =41.07, a 红 =37.84, b 红 =24.17 and L 绿 =28.69, a 绿 =1.47, b 绿 =-1.55, the specific calculation formula is as follows: D E 0=[(D L ) 2 +(D a ) 2 +(D b ) 2 ] 0.5 ; D L = L 红 - L 绿 ;D a = a 红 - a 绿 ;D b = b 红 - b 绿 ; ΔE1= [(Δ L i ) 2 +(D a i ) 2 +(D b i ) 2 ] 0.5 ; D L i = L 红 - L i ;D a i = a 红 - a i ;D b i = b 红 - b i ; S =100-(ΔE1 / Δ E 0) ×100; If the color selection standardized score S of at least 3 plants in each plot of each test site in a family is greater than or equal to 60 within 3 years, the family will be subjected to nested design variance analysis with year, test site, plot, and plant as independent variables and score as dependent variable. If the effects of year, test site, plot, and plant on the score are not significantly different, the Liquidambar variety of the family will be marked as a qualified variety, and all qualified varieties will be grouped into set B1; The growth indicators include preservation rate and leaf health; The preservation rate is the number of surviving plants in a single row of 5 plants in each plot. If the preservation rate of a family in each plot is greater than or equal to 3, the Liquidambar variety of the family is marked as a qualified variety, and all qualified varieties are grouped into set A3; The leaf health degree is obtained by scanning the collected leaves with a scanner, and then importing the scanned images into a plant image analyzer to count the areas of leaf spots, insect damage, and rot, and calculating the percentage of the sum of the areas of spots, insect damage, and rot to the total leaf area. If the leaf health degree of at least 3 plants of a family in each plot is below 10%, the liquidambar variety of the family is marked as a qualified variety, and all qualified varieties are grouped into a set B2; S4. Select the intersection of set A1, set A2 and set A3 to form set A, select the intersection of set B1 and set B2 to form set B, and then use the intersection of set A and set B as the final selected excellent color-changing family to cultivate and build a liquidambar forest according to steps S1 and S2.

2. The method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored liquidambar formosana according to claim 1, characterized in that: In step S1, seeds are collected from a single Liquidambar formosana plant in October or November, and then the seeds are soaked in water for 48 hours in January or February of the following year, and then disinfected with potassium permanganate with a concentration of 0.2%, and then spread on a sand bed for germination. Watering is performed regularly every day to keep the sand bed moist. When the sprouts grow to 1 to 2 cm 30 to 40 days after sowing, the sprouts are taken out and the roots are cut, and the main root length is retained to be 2 to 4 cm. Then the sprouts are transplanted and placed in a non-woven bag filled with a substrate, and then placed in a seedbed for cultivation.

3. The method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored liquidambar formosana according to claim 1, characterized in that: Transplant the seedlings into non-woven bags filled with substrate, and then place them in the seedbed for cultivation, using a shade net with a light transmittance of 40% to 50% for shade; apply foliar fertilizer twice a month from May to September of the same year, and stop applying foliar fertilizer after October; in the rainy season when the temperature is above 25°C, spray once every 15 days with a 0.1% methyl thiophanate aqueous solution or a 0.4% carbendazim aqueous solution. If snails are found, use 6% metaldehyde carbaryl granules for prevention and control.

4. The method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored liquidambar formosana according to claim 1, characterized in that: The matrix comprises the following components in parts by weight: 35-45 parts of humus soil, 40-50 parts of decomposed coconut bran, 4-6 parts of fermented mushroom residues, and 8-15 parts of perlite; the foliar fertilizer comprises the following components in parts by mass fraction: 0.3-0.5% of compound fertilizer, 0.1% of nitrogen fertilizer, and the balance is water.

5. The method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored liquidambar formosana according to claim 1, characterized in that: The ratio of N:P2O5:K2O in the compound fertilizer is 15:15:15; and the nitrogen fertilizer is urea.

6. The method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored liquidambar formosana according to claim 1, characterized in that: In step S2, the soil is loosened and weeded once in July and August every year. Specifically, the weeds and shrubs that affect the growth of trees in the forest are cut down, and the soil is loosened within a range of 50 cm to the left and right, 60 cm above, 40 cm below, and 20 cm deep, centered on the plant.

7. The method for breeding improved varieties of Liquidambar formosana based on leaf color evaluation of colored liquidambar formosana according to claim 1, characterized in that: In step S3, the color change amount of a single plant is the percentage of the number of colored leaves of each Liquidambar formosana plant to the total number of leaves, and the color change amount of a single plant is set to 11 gradients, with each 10% being a gradient. The color change amount of a single plant when all leaves have not changed color is 0%, and the color change amount of a single plant when all leaves have changed color is 100%.

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