A method for shortening the breeding period of rubber trees

Abstract

The present invention provides a systematic breeding method for shortening the breeding period of rubber trees, which solves the technical problems in the prior art that the breeding time of rubber trees is too long and is not conducive to the breeding and development of new rubber tree varieties. It includes the following steps: S1, screening of excellent individual plants; S2, rejuvenation in the field and large-scale propagation; S3, trait identification; S4, field planting verification; S5, according to steps S3 and S4, varieties with excellent disease resistance, cold resistance, drought resistance, fast growth, high latex yield and good growth adaptability can be screened out. A systematic breeding method that can effectively shorten the breeding period of rubber trees disclosed by the present invention can shorten the breeding time of new rubber tree varieties from 30 years to within 15 years, greatly shortening the breeding time limit of new varieties, and is of great significance to rubber tree breeding.

Description

Technical Field

[0001] The present invention relates to the field of rubber tree breeding, and particularly relates to a method for shortening the breeding period of rubber trees. Background Art

[0002] Natural Rubber (NR), as an important strategic material and industrial raw material globally, is mainly produced from rubber trees (Hevea brasiliensis Muell.-Arg.), a tree species native to the Amazon River Basin in Brazil and later introduced to various tropical regions around the world. The development of rubber tree breeding technology is of great significance for improving the yield, quality, and sustainable development of natural rubber. The traditional rubber tree breeding cycle is extremely long, generally taking about 30 years, and this process includes multiple stages such as "sexual hybridization, progeny selection, and clone selection". Due to the special production cycle and complex measurement procedures of rubber trees, researchers often need to consume a large amount of time and resources to complete the breeding of a new variety. At the same time, the long breeding cycle of traditional rubber tree breeding restricts the rapid popularization and application of new rubber tree varieties, especially when dealing with climate change and market demand changes.

[0003] For a long time, the main challenges faced in rubber tree breeding include a long breeding cycle, low efficiency, and the contradiction between high yield and resistance. In addition, the breeding materials of rubber trees mostly originate from a narrow genetic background, resulting in limited exploration and utilization of excellent gene resources, and the breeding bottleneck is becoming increasingly prominent. To break through this bottleneck, researchers have been exploring new breeding technologies and methods in order to shorten the breeding cycle, improve breeding efficiency, and cultivate new rubber tree varieties with higher yield and multiple resistances.

[0004] In recent years, through early identification technologies such as molecular marker-assisted selection and physiological index measurement, the stress resistance and yield of rubber trees can be predicted early. However, these early prediction methods have the problem of low accuracy. To obtain high-resistant and high-yield varieties in actual production, it is still necessary to go through many years of variety comparison tests and regional tests, and the breeding cycle is more than 30 years. Therefore, developing a new method that can effectively shorten the breeding period of rubber trees has important practical significance for improving the breeding efficiency and success rate of rubber trees.

[0005] The applicant of the present invention has found that the prior art has at least the following technical problems:

[0006] 1. In the prior art, the breeding time of rubber trees is too long and the efficiency is low, which is not conducive to the development and utilization of new rubber tree varieties;

[0007] 2. In the prior art, due to low breeding efficiency, the variety is single and cannot meet the planting requirements of the diversity of planting environments.

[0008] 3. In the prior art, the breeding time of rubber trees is as long as 30 years, and the determination and promotion of new varieties are slow, which hinders production and utilization. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for shortening the breeding period of rubber trees, so as to solve the technical problem that the existing rubber tree breeding technology uses traditional cross-breeding, which takes about at least 30 years. Due to the long breeding time, it is not conducive to the breeding and development of new rubber tree varieties. The preferred technical solutions among the many technical solutions provided by the present invention and the many technical effects that can be produced are described in detail below.

[0010] To achieve the above purpose, the present invention provides the following technical solutions:

[0011] A method for shortening the breeding period of rubber trees provided by the present invention includes the following steps:

[0012] S1 Superior individual plant screening: In the first year, from April to October, for the population of seedling trees that have been tapped for more than 5 years, superior individual plants are screened, and scions are collected;

[0013] First, seedling trees with high latex production are screened; at the same time, the superior individual plants should also have at least two of the following target traits: resistance to powdery mildew, cold resistance, drought resistance, fast growth, and a straight and smooth trunk;

[0014] The scions of the selected superior individual plants are screened according to the following conditions: the stem diameter is more than 8 mm, the length is more than 8 cm, with apical buds, and facing the sun, and the bud points are plump;

[0015] S2 Field rejuvenation and mass propagation

[0016] S21 Grafting: The scions collected in S1 are grafted onto 1 - 3-year-old rootstocks by the branch combination method or the bud grafting method; after the leaf buds sprout and the interfaces heal, they are untied in the same year to establish clones;

[0017] S22 Bud grafting propagation: In the second year, from July to September, when the scions grow 3 - 4 whorls of leaves and are 60 - 100 cm tall, axillary buds on the scions in S21 are used for bud grafting propagation to increase the number of plants; after the bud grafting survives, the rootstocks are sawed off in the same year to make the bud pieces germinate to form grafted plants, and the axillary buds and scale buds within 15 cm of the stem base are removed when the first whorl of leaves is stable;

[0018] S23 Promote rooting: In the third year, from February to June, the main stem is bent to promote the adventitious buds at the base to germinate into upright-growing plants; when the first whorl of leaves is stable, the axillary buds and scale buds within 15 cm of the lower part of the stem are removed, the stem is tied with thick thread at 5 - 10 cm below, the stem is scratched at multiple places within 3 cm above the tying position, coated with naphthalene acetic acid solution, and then covered with soil to a position 10 cm above the wound to promote adventitious roots to grow on the stem;

[0019] S24 Obtaining graftable bud sticks: In the 4th year, from April to June, check the growth of adventitious roots. Bend the stem of the plant with adventitious roots, pay attention to removing buds, and promote the germination of adventitious buds near the adventitious roots to grow into a stem with good erectness and fast growth rate; the stem has multiple bud chips with excellent traits, and graftable bud sticks are obtained;

[0020] S3 Character identification

[0021] Using the clones obtained after large-scale propagation in the 2nd year as materials, conduct field drought stress experiments and field low-temperature stress experiments on seedlings, and evaluate the gum production during the seedling stage. Comprehensively screen out excellent clones with high yield and high resistance; this step is carried out synchronously with step S23 and step S24;

[0022] S4. Field planting verification

[0023] S41 Propagation of excellent clones: Based on the excellent clones with high yield and high resistance screened in S3, correspondingly select the juvenile bud sticks of the same clone obtained in S24, and conduct juvenile bud stick budding propagation in the 5th year to obtain juvenile excellent clone seedlings;

[0024] S42 Multi-point layout of field planting verification in potential promotion areas

[0025] While propagating in the 5th year, select a systematic measurement point in the breeding area. Select multiple plots as verification points from sunny slopes or shady slopes with altitudes ranging from 100 to 1200 m in the potential promotion area, including upper slopes, middle slopes or foot of slopes. Plan to plant the juvenile excellent clones propagated in S41, set 2 replicates for each clone, and plant 30 plants in each replicate; set a control variety at each test point;

[0026] S43 Seedling planting and management

[0027] In the 6th year, from May to August, plant seedlings at each point selected in S42; after planting, water thoroughly, promptly remove leaf buds and the buds sprouted from seedlings, observe the occurrence of pest and disease damage at any time, and spray pesticides in a timely manner;

[0028] From the 7th year to the 14th year, conduct routine cultivation and management of the seedlings at each point according to the "NY / T 221-2016 Rubber tree cultivation technical regulations". Measure the annual growth of the tree body in the middle and late December every year. The measurement standard is the stem girth at 1.3 m above the ground, and record the data well; when it comes to the 11th year of breeding, conduct an analysis of the tree body growth, screen out plants with a stem girth ≥ 50 cm, and tap rubber in the next year;

[0029] S44 Verification of powdery mildew resistance

[0030] From the 7th year to the 14th year, the powdery mildew resistance of the tested clones at each point was observed according to the "Technical Regulations for Forecasting Powdery Mildew of Hevea brasiliensis (NY / T 1089-2015)", and the repeatability assessment was carried out with the disease resistance ability identified in S3.

[0031] S45 Determination and evaluation of latex yield

[0032] In the 12th year, according to the climate environment at each point and the stability of the leaf canopy of rubber trees, tapping was carried out from September to January of the following year, and the dry rubber yield per knife per plant was recorded. After tapping, the average latex yield per plant of the clones and the yield stability among plants within the clones were analyzed;

[0033] In the 13th year - 15th year, according to the plant growth amount, latex yield, and stress resistance traits at each verification point, combined with the corresponding traits of the plants at the systematic determination points in the breeding area in step S42, the repeatability assessment of excellent traits and the acceptability assessment of defective traits were carried out to determine excellent clones and their suitable planting areas;

[0034] S46 DUS testing

[0035] Synchronously, in the 13th year - 15th year, the excellent clones selected in step S45 were subjected to DUS testing according to the requirements of the "Guidelines for the Conduct of Tests for Distinctness, Uniformity and Stability - Hevea brasiliensis (NY / T 2749-2015)";

[0036] From the 14th year to the 15th year, combined with the comprehensive evaluation results of stress resistance, latex yield, and small - area adaptability in steps S3 and S4, small - scale production - type promotion planting was carried out in suitable areas;

[0037] S5. According to steps S3 and S4, new rubber tree varieties with excellent stress resistance, latex yield, and growth adaptability can be screened out.

[0038] Furthermore, in step S23, the mass percentage concentration of the naphthalene acetic acid solution is 3% - 4%.

[0039] Furthermore, in step S23, the mass percentage concentration of the naphthalene acetic acid solution is 3.5%.

[0040] Furthermore, in step S3, the specific field drought stress experiment for seedlings is as follows: The plants obtained after large - scale propagation in the 2nd year are transplanted into flower pots. Ditches are dug in the field, the flower pots are placed in the ditches, bricks are placed at the bottom to isolate water absorption, and a shading net is covered on the upper surface to ensure that only drought stress is received and not affected by the day - night temperature difference. After implementing the stress, the tissue water content (PWD), protective enzymes (SOD, POD), malondialdehyde (MDA), soluble protein (SP), and recovery ability indicators are measured at time - length gradients to analyze the drought resistance and drought tolerance of each clone, and the comprehensive evaluation of the availability in production;

[0041] Synchronously, evaluate the spatial distribution characteristics of chlorophyll in different leaf positions of seedlings without drought stress, and measure the SPAD value and leaf color change of leaves at different development stages;

[0042] Synchronously, measure the anatomical structure of the upper and middle parts of the middle leaflets of mature leaves of normally growing seedlings, including: leaf thickness, upper epidermis thickness, palisade tissue thickness, spongy tissue thickness, lower epidermis thickness, vein thickness, and leaf compactness.

[0043] Further, in step S3, the low-temperature stress experiment on seedlings in the field is specifically as follows: using the plants obtained after large-scale propagation in the second year as materials, controlling the constant low temperature stress at 3°C through an incubator, collecting leaf samples every 2 days to measure the relative conductivity, and after 8 days of stress, recovering at room temperature for 1 day, and then measuring the relative conductivity again;

[0044] Synchronously, implement temperature gradient measurement: select healthy current-year branches, collect the green branches of the second leaf cluster from top to bottom, and conduct in vitro low-temperature stress; cool down at a rate of 4°C per hour, set 4 temperature gradients of 4°C (CK), 0°C, -2°C, and -5°C, maintain the stress at a constant temperature for 12 hours, and then heat up to room temperature at a rate of 4°C per hour and take out to measure the relative conductivity of the branch bark.

[0045] Further, in step S4, the control variety set is the variety planted in the local productive planting area of the planting site.

[0046] Based on the above technical solutions, the embodiments of the present invention can at least produce the following technical effects:

[0047] (1) The systematic breeding method provided by the present invention that can effectively shorten the breeding period of rubber trees can shorten the rubber tree breeding process from 30 years to within 15 years, greatly shortening the breeding time limit of new varieties, improving the breeding efficiency, and being of great significance to rubber tree breeding.

[0048] (2) The systematic breeding method provided by the present invention that can effectively shorten the breeding period of rubber trees can screen out new rubber tree varieties with excellent stress resistance, yield, and growth adaptability while greatly shortening the breeding period. Therefore, the rubber tree breeding method in the present invention also has the advantage of excellent breeding effects.

[0049] (3) The systematic breeding method provided by the present invention that can effectively shorten the breeding period of rubber trees can obtain new rubber tree varieties suitable for planting in multiple planting sites with different altitudes and slope aspects because multiple plots with altitude and slope aspect differences are selected as test sites. Therefore, it improves the rubber tree breeding efficiency, increases the rubber tree variety diversity, and can meet the planting requirements of environmental diversity. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0051] Figure 1 It is the field drought stress experiment diagram in the embodiment;

[0052] Figure 2 It is the schematic diagram of the leaf anatomical structure in the embodiment;

[0053] Figure 3 It is the entire breeding technology roadmap in the embodiment;

[0054] Figure 4 It is the thumbnail of the seedling treatment and growth in the entire breeding cycle in the embodiment;

[0055] Figure 5 It is the latex production of the rejuvenated and propagated clones in the embodiment (7-year-old Yunyan 314, actually the 13th year of breeding);

[0056] Figure 6 It is the latex production of the rejuvenated and propagated clones in the embodiment (9-year-old Yunyan 272, actually the 15th year of breeding);

[0057] Figure 7 It is the stable leaf canopy morphology diagram of the young leaves of Yunyan 272 in January 2018 in the embodiment;

[0058] Figure 8 It is the stable leaf canopy morphology diagram of the big leaves of Yunyan 272 in February 2022 in the embodiment. Specific Embodiments

[0059] To make the purpose, technical solutions and advantages of the present invention clearer, the following will describe the technical solutions of the present invention in detail. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present invention.

[0060] In the following Example 1, the following were respectively carried out: drought resistance evaluation, drought resistance evaluation (physiological indexes), cold resistance evaluation (anatomical structure), cold resistance evaluation (seedlings), and yield evaluation (in vitro young stems); all were carried out with Yunyan 77-4 as the control, and Yunyan 272, Yunyan 314, and Yunyan 617 were respectively the names of the new rubber tree varieties during the cultivation process.

[0061] Example 1:

[0062] The present invention provides a method for shortening the breeding period of rubber trees, comprising the following steps:

[0063] S1 Screening of excellent individual plants:

[0064] In the first year (2009), from April to October, select seedling excellent individual plants from the growing rubber plantations in Jinghong, Menghai, Dehong, Hekou, Pu'er, and Wenshan rubber-growing areas in Yunnan Province, and collect scions;

[0065] The screening of excellent individual plants takes high rubber yield as the first goal. At the same time, the excellent individual plants should also have at least two of the following target traits: powdery mildew resistance, cold resistance, drought resistance, fast growth, and straight and smooth tree trunks;

[0066] The scions of the selected excellent individual plants are screened according to the following conditions: stem diameter above 8 mm, length above 8 cm, with apical buds, and sunny, with plump bud points;

[0067] S2 Field rejuvenation and large-scale propagation

[0068] S21 Grafting: Graft the scions collected in S1 onto two-year-old rootstocks by means of branch joining method and budding method; untie the bindings in the same year after the leaf buds germinate and the interfaces heal, and establish clones;

[0069] S22 Budding propagation: In the second year (2010), from July to September, when the scions grow 3 - 4 flushes of leaves and are 60 - 100 cm tall, use the axillary buds on the scions in S21 to carry out budding propagation to increase the number of plants; after the budding survives, saw off the rootstocks in the same year to make the bud pieces germinate to form grafted plants, and use a sharp knife to remove the axillary buds and scale buds within 15 cm of the stem base when the first flush of leaves is stable;

[0070] S23 Promote rooting: In the third year (2011), from February to June, bend the main stem to promote the adventitious buds at the base to germinate into upright-growing plants; when the first flush of leaves is stable, use a sharp knife to remove the axillary buds and scale buds within 15 cm of the lower part of the stem, tie the stem with thick thread at 5 - 10 cm above the lower part, make multiple cuts on the stem within 3 cm above the tying position, apply a naphthalene acetic acid solution with a concentration of 3.5% to the cut wounds, and then cover the soil to 10 cm above the wound site to promote the stem to produce adventitious roots;

[0071] S24 Obtain graftable bud sticks: In the fourth year (2012), from April to June, check the growth of adventitious roots, bend the stem of the plants with adventitious roots, pay attention to removing buds, and promote the adventitious buds near the adventitious roots to germinate and grow into stems with good uprightness and fast growth; the stem has multiple bud pieces with excellent traits, and then use the budding method to carry out large-scale propagation to obtain graftable bud sticks;

[0072] S3 Character identification

[0073] Using the clones obtained after the second-year large-scale propagation (step S22) as materials, conduct field drought stress experiments and field low-temperature stress experiments on seedlings, and evaluate the gum production during the seedling stage. Comprehensively screen out excellent clones with high yield and high resistance; this step is carried out simultaneously with steps S23 and S24;

[0074] S31 Field drought stress experiment on seedlings ( Figure 1 as shown) specifically is as follows:

[0075] Transplant the plants obtained after the second-year large-scale propagation into flowerpots with a diameter of 40 cm and a depth of 60 cm. Dig trenches in the field, place the flowerpots in the trenches, pad bricks at the bottom to isolate water absorption, and cover the upper surface with a shading net to ensure that only drought stress is received and not affected by the diurnal temperature difference. After the stress is applied, measure indicators such as tissue water content (PWD), protective enzymes (SOD, POD), malondialdehyde (MDA), soluble protein (SP), and recovery ability at different time length gradients, analyze the drought resistance and drought tolerance of each clone, and comprehensively evaluate the availability in production;

[0076] Synchronously, study the spatial distribution characteristics of chlorophyll in different leaf positions of non-drought-stressed seedlings, and measure the SPAD value and leaf color change at different development stages of the leaves;

[0077] Specific experimental implementation steps and results: The drought stress treatment is carried out by the natural drying method. Using Yunyan 77-4 as a control, evaluate the drought resistance of Yunyan 272, Yunyan 314, and Yunyan 617. Conduct soil drought stress in late May 2011. After thoroughly watering the soil for 3 consecutive days, stop watering and let it dry naturally. During the stress period, keep the temperature and humidity in the nursery consistent with the surrounding soil environment and prevent the interference of natural precipitation. Take leaf samples at 0 (CK), 5, and 10 days after water cut-off to measure various physiological indicators. Select 5 plants with basically the same growth for each clone to collect leaf samples mixedly. Quick-freeze the leaf samples in cryotubes and store them in liquid nitrogen, and then bring them back to the laboratory to measure various physiological indicators. The results are shown in Table 1.

[0078] Table 1 Measurement results of physiological indicators of rubber tree clones under drought stress

[0079]

[0080] The results in Table 1 show that during the drought stress process, with the extension of the water cut-off time, the SOD / POD content of Yunyan 272 and Yunyan 314 first increased and then decreased, the MDA content showed an upward trend, the SP content first increased and then decreased. When the stress reached 5 days, the values of SOD, POD, and SP reached the maximum. The SP content of Yunyan 272 had the largest increase, followed by Yunyan 314. Considering all indicators, the most drought-resistant variety among the tested varieties is Yunyan 272.

[0081] Synchronously, the anatomical structure of the upper middle leaflets of mature leaves of normally growing seedlings was measured, including: leaf thickness, upper epidermis thickness, palisade tissue thickness, spongy tissue thickness, lower epidermis thickness, leaf vein thickness, and leaf compactness. As Figure 2 shown in Table 2.

[0082] Table 2 Multiple comparisons among the leaf anatomical structure indexes of the rubber tree clones tested

[0083]

[0084] Note: The data in Table 2 are the averages of 54 groups of data for each index. Different capital and lowercase letters after the data in the same row indicate extremely significant differences (P < 0.01) and significant differences (P < 0.05), respectively.

[0085] Table 3 Subordinate function evaluation of the leaf anatomical structure of the rubber tree clones tested

[0086]

[0087] The results in Table 2 and Table 3 show that there are significant differences in the anatomical structure among different clones. Principal component analysis was performed on them, and finally 7 indexes characterizing drought resistance were screened out, including upper epidermis thickness, lower epidermis thickness, palisade tissue thickness, spongy tissue thickness, palisade-to-spongy ratio, leaf compactness, and leaf thickness; the results of the drought tolerance evaluation by the subordinate function analysis method show (Table 3) that the drought resistance of the 4 clones from strong to weak is: Yunyan 617 > Yunyan 272 > Yunyan 77 - 4 > Yunyan 314.

[0088] The specific low-temperature stress experiment in the field for S32 seedlings is as follows:

[0089] Using the plants obtained after large-scale propagation in the second year as materials, 3℃ low-temperature constant stress was controlled by an incubator. Leaf samples were collected every 2 days to measure the relative electrical conductivity. After 8 days of stress, they were restored at normal temperature for 1 day, and then the relative electrical conductivity was measured again.

[0090] The specific experimental implementation steps and results: Using seedlings as materials, 3℃ low-temperature constant stress was controlled by an incubator. Leaf samples were collected every 2 days to measure the relative electrical conductivity. After 8 days of stress, they were restored at normal temperature for 1 day and then measured again. The measured data are shown in Table 4.

[0091] Table 4 Relative electrical conductivity of the rubber tree clone seedlings after low-temperature stress (unit / %)

[0092]

[0093] The results in Table 4 show that on the 4th day of stress, both Yunyan 272 and Yunyan 77-4 were basically not damaged. When stressed to 6 days and 8 days, Yunyan 77-4 was significantly damaged, but Yunyan 272 and Yunyan 617 were slightly damaged. After 1 day of recovery, the measured data was not much different from that at 8 days of stress. This indicates that Yunyan 272 has more obvious low-temperature tolerance and recovery ability.

[0094] Specific experimental implementation steps and results: Implement temperature gradient measurement. Select healthy current-year branches, and collect green branches from the second leaf cluster from top to bottom as materials for in vitro low-temperature stress. Cool down at a rate of 4°C per hour, set 4 temperature gradients of 4°C (CK), 0°C, -2°C, and -5°C, carry out constant-temperature stress for 12 hours, and then heat up to room temperature at a rate of 4°C per hour and take out to measure the relative conductivity of the branch bark. The measurement results are shown in Table 5.

[0095] Table 5 Relative conductivity of the young stems of the rubber tree clones after in vitro low-temperature stress (unit / %)

[0096]

[0097] The results in Table 5 show that among the 4 clones tested, Yunyan 272 is the most cold-resistant, Yunyan 314 is slightly stronger than Yunyan 77-4 (CK), and the second-ranked is Yunyan 617.

[0098] S4. Field planting verification

[0099] S41 Propagation of excellent clones:

[0100] Based on the clones with strong stress resistance screened in S3, select the young shoot cuttings of the corresponding clones obtained in S24, and carry out budding propagation of the young shoot cuttings in the 5th year (2013) to obtain young excellent clones;

[0101] S42 Layout of field planting verification in multiple points and multiple regions

[0102] While propagating in the 5th year (2013), establish a systematic measurement point in Jinghong City, Yunnan Province, and select plots with different altitudes and slopes in Gengma County, Lincang City, Hekou County, Honghe Prefecture, and Ruili City, Dehong Prefecture, and plan to plant the excellent clones propagated in S41; set a control product at each test point, and select Yunyan 77-4 as the control variety;

[0103] S43 Seedling planting and management

[0104] In the 6th year (2014), from May to August, plant seedlings at each test point selected in S42; after planting, water thoroughly, promptly remove the leaf buds and the buds sprouted from the seedlings, observe the pest and disease damage situation at any time, and spray pesticides in a timely manner;

[0105] From the 7th year to the 14th year (2015 - 2022, which are the 1st - 8th years of the clonal planting experiment), rubber tree planting management was carried out in accordance with the "Technical Regulations for Rubber Tree Cultivation (NY / T 221 - 2016)". In mid - to late December each year, the annual growth of the tree body was measured. The measurement standard was the stem girth at 1.3 m above the ground, and the data was recorded well. When it came to the 11th year (the 5th year of planting at each site), the growth of the tree body could be analyzed, and germplasms with a stem girth ≥ 50 cm were selected for rubber tapping in the following year. After 11 years, the stem girth was continuously measured because the growth rates of different varieties were different, and this indicator was one of the indicators for evaluating fast - growing varieties.

[0106] S44 Powdery Mildew Identification and Multi - point Verification

[0107] From the 7th year to the 14th year, from February to March each year, in accordance with the "Technical Regulations for Monitoring Powdery Mildew of Rubber Tree (NY / T 1089 - 2015)", the resistance of the planted clones to powdery mildew at each verification site was observed. The resistance to powdery mildew was divided into several types such as "resistance to invasion, resistance to spread, tolerance to damage, and disease avoidance". And according to the powdery mildew grading standard in the "Technical Regulations for Monitoring Powdery Mildew of Rubber Tree (NY / T 1089 - 2015)", it was divided into six levels: 0, 1, 3, 5, 7, and 9.

[0108] After 10 - year investigations on clones Yunyan 774 (control), Yunyan 272, Yunyan 314, and Yunyan 617, it was found that the phenophases of Yunyan 272 and Yunyan 314 were early. In general years, the leaf canopies of big trees were stable in February, and those of young trees were stable in January ( Figure 3 ) and were identified according to the powdery mildew grading standard in the "Technical Regulations for Monitoring Powdery Mildew of Rubber Tree (NY / T 1089 - 2015)" as:

[0109] Yunyan 272 showed levels 0 - 1, was not resistant to invasion, could resist spread, tolerate damage, and avoid disease, and was easy to recover;

[0110] Yunyan 314 showed levels 1 - 3, was not resistant to invasion, not resistant to spread, slightly tolerant to damage, could avoid disease, and was easy to recover.

[0111] Yunyan 617 and Yunyan 77 - 4 were similar, showing levels 3 - 5, not resistant to invasion, not resistant to spread, slightly tolerant to damage, slightly able to avoid disease, and slightly easy to recover.

[0112] S45 Determination and Evaluation of Gum Yield

[0113] In the 12th year (2020), according to the climate environment and the stability of the leaf canopies of rubber trees at each test site, rubber tapping was carried out from September to January of the following year, and the dry rubber yield per cut of each plant was recorded. After the rubber tapping was completed, the inter - plant variation pattern of gum - producing traits within clones, the annual average yield per plant of each clone, and the gum - producing pattern within the year were analyzed; the average dry rubber yield per single plant is shown in Table 6.

[0114] Table 6 Records of Trial Tapping Yields at Measuring Points in Jinghong System (Unit: g)

[0115]

[0116] Note: The tapping period from 0403 to 0411 refers to "from April 3 to April 11", and the rest is the same.

[0117] The results in Table 6 show that Yunyan 314 has the highest yield, followed by Yunyan 272, and Yunyan 617 is comparable to the control variety Yunyan 77-4.

[0118] S46 DUS Testing and New Variety Declaration

[0119] The selected elite clones were subjected to DUS testing in accordance with the requirements of "Guidelines for the Conduct of Tests for Distinctness, Uniformity and Stability of New Varieties of Plants - Hevea brasiliensis" (NY / T 2749-2015), and simultaneously applied for the protection of new plant varieties by the Ministry of Agriculture and Rural Affairs;

[0120] In the 14th - 15th years (2022 - 2023), combining the comprehensive evaluation results of stress resistance, latex production and small - area adaptability in Steps S3 and S4, production - scale small - scale promotion and planting were carried out in suitable areas;

[0121] S5. By combining Steps S3 and S4, varieties with excellent stress resistance, yield and growth adaptability can be screened out; the specific breeding technical route is as Figure 3 shown. The schematic diagram of the whole - cycle plant treatment and growth situation is as Figure 4 shown; Figure 4 In it, in the order of the arrow direction: the selected elite individual plants → grafting of scions from elite individual plants → rejuvenation propagation: adventitious buds sprouted at the base of the plant after bending the clones grafted with bud chips after the scions germinated → growth situation of rejuvenated branches → growth situation of two - leaf canopies of rejuvenated branches → situation when the rejuvenated branches grow to three - leaf canopies, which can be used for budding and propagation → leaf canopies sprouted after budding and propagation of rejuvenated bud strips → growth situation of plants in the rejuvenated clone comparison plot.

[0122] As mentioned above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention.

Claims

1. A method for shortening the rubber tree breeding period, characterized in that: The steps include: S1 Selection of high-quality individual plants: In the first year, from April to October, select high-quality individual plants from the rubber tapping population for more than 5 years and collect scions; First, select the seedling trees with high rubber production; at the same time, the excellent individual trees must also have at least two of the following target traits: resistance to powdery mildew, cold resistance, drought resistance, fast growth, and straight and smooth trunks; The scions of excellent individual plants were collected and screened according to the following conditions: stem thickness of more than 8mm, length of more than 8cm, with terminal buds, facing the sun, and full buds; S2 Field rejuvenation and expanded reproduction S21 Grafting: Graft the scions collected in S1 onto 1-3 year old rootstocks by branch grafting or bud grafting. After the leaf buds emerge and the joints heal, untie them in the same year to establish a clone system. S22 budding propagation: In the second year, from July to September, when the scion grows 3-4 leaves and is 60-100cm high, use the axillary buds on the S21 scion to carry out budding propagation to expand the number of plants; after the budding survives, saw the stock in the same year to make the buds germinate to form grafted plants, and remove the axillary buds and scale buds within 15cm of the stem base when the first leaf is stable; S23 Promote rooting: In the third year, from February to June, bend the main stem to promote the germination of the adventitious buds at the base into upright plants; when the first leaf is stable, remove the axillary buds and scale buds within 15 cm below the stem, tie the stem with thick wire at the lower 5-10 cm, make multiple cuts on the stem within 3 cm above the binding position, apply naphthaleneacetic acid solution, and then cover the soil to 10 cm above the wound to promote the production of adventitious roots in the stem; S24 Obtaining buds that can be grafted: In the fourth year, from April to June, check the growth of adventitious roots, bend the stems of plants with adventitious roots, and pay attention to removing buds to promote the germination of adventitious buds near the adventitious roots, so that they grow into stems with good uprightness and fast growth; if the stems have multiple buds with excellent traits, we can obtain buds that can be grafted; S3 Trait Identification Using the clones obtained after the second year of expanded propagation as materials, conducting seedling field drought stress experiments and seedling field low temperature stress experiments, as well as evaluating the rubber yield at the seedling stage, comprehensively screening out high-yield and high-resistance clones; this step is performed simultaneously with step S23 and step S24; S4. Field Planting Verification S41: Propagation of excellent clones: Based on the high-yield and high-resistance excellent clones selected in S3, the young buds of the same clone obtained in S24 are selected accordingly, and the young buds are budded and propagated in the fifth year to obtain young excellent clone seedlings; S42 Field planting verification in multiple locations in potential promotion areas During the fifth year of propagation, a systematic measurement point was selected in the breeding field. Multiple plots were selected from sunny or shady slopes, upper slopes, middle slopes or slope feet at an altitude of 100-1200m in the potential promotion area as verification points. The young and excellent clones propagated in S41 were planned to be planted. Two replicates were set for each clone, and 30 plants were planted in each replicate. A control variety was set at each test point. S43 Seedling planting and management In the sixth year, from May to August, seedlings were planted at various points selected in S42. After planting, the seedlings needed to be watered thoroughly, leaf buds and buds of seedlings were promptly removed, pests and diseases were observed at any time, and pesticides were sprayed at appropriate times. From the 7th to the 14th year, routine cultivation and management are carried out on the seedlings at each site. The annual growth of the trees is measured in mid-to-late December each year. The measurement standard is the stem circumference at 1.3m above the ground, and the data are recorded; When the breeding season reaches the 11th year, the tree growth analysis is conducted and plants with stem circumference ≥ 50 cm are selected for tapping in the next year. S44 Powdery Mildew Resistance Verification From the 7th to the 14th year, the powdery mildew resistance of the clones tested at each site was observed; S45 Rubber production measurement and evaluation In the 12th year, rubber tapping was carried out from September to January of the following year, based on the climate and stability of the rubber leaves at each location. The dry rubber yield of each plant was recorded. After the tapping was completed, the average rubber yield per plant of the clones and the yield stability between plants within the clones were analyzed. In the 13th to 15th year, based on the growth, rubber yield, and stress resistance of the plants at each verification point, combined with the corresponding traits of the plants at the systematic measurement points in the breeding site in step S42, the repeatability of the superior traits and the acceptability of the inferior traits are evaluated to determine the superior clones and their suitable planting areas; S46 DUS test Simultaneously, in the 13th to 15th year, the superior clones selected in step S45 are subjected to DUS test; In the 14th to 15th year, based on the comprehensive evaluation results of stress resistance, rubber yield and small-area adaptability in steps S3 and S4, small-scale production promotion planting is carried out in suitable areas; S5. According to step S3 and step S4, new varieties of rubber trees with excellent stress resistance, rubber yield and growth adaptability can be screened out.

2. The method for shortening the rubber tree breeding period according to claim 1, wherein: In step S23, the mass percentage concentration of the naphthylacetic acid solution is 3%-4%.

3. The method for shortening the rubber tree breeding period according to claim 1, wherein: In step S23, the mass percentage concentration of the naphthylacetic acid solution is 3.5%.

4. The method for shortening the rubber tree breeding period according to claim 1, wherein: In step S3, the seedling field drought stress experiment is specifically as follows: the plants obtained after the second year of expanded reproduction are transplanted into flower pots, trenches are dug in the field, the flower pots are placed in the trenches, bricks are placed underneath to isolate water absorption, and a shading net is covered on the top to ensure that only drought stress is applied but not affected by the temperature difference between day and night. After the stress is applied, the tissue water content, protective enzymes, malondialdehyde, soluble protein, and recovery capacity index are measured in a time gradient, the drought resistance and drought tolerance of each clone are analyzed, and the availability in production is comprehensively evaluated; Synchronously, the spatial distribution characteristics of chlorophyll at different leaf positions of seedlings without drought stress were studied, and the SPAD values ​​and leaf color changes at different developmental stages of leaves were determined; Synchronously, the anatomical structures of the middle and upper parts of the middle leaflets of mature leaves of normally growing seedlings were measured, including leaf thickness, upper epidermis thickness, palisade tissue thickness, spongy tissue thickness, lower epidermis thickness, vein thickness, and leaf compactness.

5. The method for shortening the rubber tree breeding period according to claim 1, wherein: In step S3, the seedling field low temperature stress experiment is specifically as follows: using the plants obtained after the second year of expansion and propagation as materials, controlling the low temperature and constant temperature stress at 3°C ​​in an incubator, collecting leaf samples every 2 days to measure the relative conductivity, restoring to normal temperature for 1 day after 8 days of stress, and measuring the relative conductivity again; Simultaneously, temperature gradient measurement was carried out: healthy branches of the current year were selected, and the second green branch with leaf canopy from the top was collected, and subjected to in vitro low-temperature stress; the temperature was lowered at a rate of 4°C per hour, and four temperature gradients of 4°C, 0°C, -2°C, and -5°C were set, and constant temperature stress was applied for 12 hours, and then the temperature was raised to room temperature at a rate of 4°C per hour, and the relative conductivity of the branch bark was measured.

6. The method for shortening the rubber tree breeding period according to claim 1, wherein: In step S4, the control variety set is a variety that is productively planted locally at the planting site.

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