Cotton overall drought resistance grading system evaluation method and application thereof

Abstract

The invention aims to provide the evaluation method for the integral drought resistance grading system of the cotton, the phenotype condition and the yield character of the F2 single plant in the flowering and boll-forming period and the boll opening period are combined, the drought resistance of a breeding group can be evaluated by utilizing an integral drought resistance grading mode, and a breeding material with excellent drought resistance and yield can be quickly and efficiently obtained; the evaluation method for the overall drought resistance grading system of the cotton, provided by the invention, is of great significance in improving the yield and quality of the cotton, promoting breeding and improvement, coping with climate changes, improving industrial sustainable development and evaluating the drought resistance in a multi-dimensional manner. Not only is the development of the cotton industry promoted, but also valuable experience and methods are provided for drought resistance research of other crops.

Description

Technical Field

[0001] The present invention relates to the technical field of plant phenotype identification, and in particular to the technical field of overall drought resistance evaluation and verification of cotton. Background Art The complexity of drought resistance-related trait indicators determines the difficulty of evaluating drought resistance of plants. In the process of evaluating cotton drought resistance, a single trait indicator may not represent the overall drought resistance of cotton to a certain extent, and the selection of multiple trait indicators is extremely labor-intensive when evaluating a large population. Therefore, how to reasonably select appropriate trait indicators and drought resistance evaluation methods is a necessary stage in our breeding of excellent drought-resistant varieties.

[0002] The earliest phenotypic basis for drought resistance identification is the wilting phenomenon of plants under drought stress. Based on the time and degree of wilting, the wilting coefficient identification method was established. This reflects the overall changes in plant response to drought stress. Although it is relatively rough, it is still used when facing large-scale or highly separated individual phenotypic surveys. At present, based on the complexity of plant drought resistance, multiple trait indicators are usually selected for comprehensive evaluation of drought resistance, such as morphological indicators such as plant height, leaf area, and root system, photosynthetic indicators such as net photosynthetic rate, transpiration rate, and stomatal conductance, and physiological indicators such as proline, malondialdehyde, and reactive oxygen. At the same time, in order to reasonably and comprehensively analyze the drought resistance of plants, a variety of calculation methods have been used to evaluate the drought resistance of crops, such as drought resistance coefficient, membership function analysis, principal component analysis, gray correlation analysis, and comprehensive drought resistance measurement values. This series of evaluation methods have their own characteristics, but are relatively complex, and the trait investigation work and calculations are relatively heavy. The identification of drought resistance based on population materials with a large number of individuals and focusing on key phenotypes according to the currently available drought resistance identification methods are of great research significance.

[0003] Xinjiang has the climate characteristics of an arid and semi-arid region and has always been the main cotton-growing region in my country. Research on the drought resistance of cotton is of great significance to the economic development of the cotton industry in Xinjiang. Breeding and promoting drought-resistant cotton varieties is one of the effective ways to promote the sustainable and stable development of cotton production. However, the complexity of drought-resistant related traits has increased the difficulty of drought resistance evaluation for large germplasm resources. At present, a method for rapid and efficient breeding of drought-resistant and high-yield breeding materials is urgently needed. Summary of the invention

[0004] In view of the relatively complex drought resistance identification and evaluation methods in the prior art, the heavy trait investigation work and calculation, as well as the huge F2 hybrid population in the breeding process, the complexity of the identification of individual drought resistance-related phenotypes, the non-repeatability and the unpredictability of the ability to recover after drought stress, the present invention aims to provide a cotton overall drought resistance grading system evaluation method, combined with the F2 individual plant phenotypic conditions and yield traits at the flowering and boll stage and the boll opening stage, the overall drought resistance grading method can be used to evaluate the drought resistance of the breeding population, and breeding materials with excellent drought resistance and yield can be obtained quickly and efficiently. The cotton overall drought resistance grading system evaluation method provided by this application is of great significance for improving cotton yield and quality, promoting breeding and improvement, coping with climate change, enhancing the sustainable development of the industry, and evaluating drought resistance in multiple dimensions. It not only helps to promote the development of the cotton industry, but also provides a valuable method for drought resistance research of other crops.

[0005] To achieve this technical purpose, the present invention adopts the following technical solutions: The present invention provides a method for evaluating the overall drought resistance grading system of cotton, and the evaluation method specifically comprises the following steps: S1. Determine the cotton varieties to be evaluated; S2. Under drought stress treatment and control conditions, the flowering and boll opening period indexes of the selected cotton varieties were measured; S3. The drought resistance grade of the flowering and boll period is obtained according to the individual plant, leaf and boll conditions of the selected cotton plants in step S2; S4. According to the cotton boll opening situation of the selected cotton plants in step S2., the drought resistance grade during the cotton boll opening period is obtained; S5. Calculate the final drought resistance grade according to the drought resistance grade at the flowering and boll stage obtained in step S3 and the drought resistance grade at the boll opening stage obtained in step S4, the final drought resistance grade = drought resistance grade at the flowering and boll stage * 40% + drought resistance grade at the boll opening stage * 60%, and the result grades are retained as integers; S6. Evaluate the drought resistance grade according to the final drought resistance grade obtained in step S5, and screen materials with excellent drought resistance and yield based on the single boll weight index.

[0006] The evaluation criteria for drought resistance grade at flowering and bolling stage in step S3 of the evaluation method are as follows: Level 1: The leaves are basically not yellow, but dark green. The leaves at the lower nodes are not yellow. The leaves as a whole will wilt slightly in hot weather. The wilting will be relieved after overnight. The boll rate is slightly affected, which is reflected in the shedding of a small amount of cotton buds. Level 2: 25-50% of the leaves turn yellow near the petiole 1 / 3, the leaves at the lower node turn yellow but do not fall off, a small number of leaves dry up, most of the wilting leaves will ease after overnight, and the cotton bud boll rate is moderately affected; Level 3: 50-75% of the leaves turn yellow near the 2 / 3 of the petiole, 1-2 leaves fall off at the lower node, the upper cotton buds dry up and fall off, a small number of wilted leaves will be relieved after overnight, and the boll formation rate is severely affected; Level 4: All leaves turn yellow, more than 2 leaves fall off at the lower nodes, leaves wilt severely, and the wilt does not improve overnight, which has a serious impact on the boll setting rate.

[0007] The evaluation criteria for drought resistance grade at the boll opening stage in step S4 of the evaluation method are as follows: Level 1: 8-9 or above bells; Level 2: 6-7 bells; Level 3: 4-5 bells of cotton wool; Level 4: 3 or fewer bells.

[0008] Furthermore, the present application also provides an evaluation method for an overall drought resistance grading system for cotton and its application in cotton breeding.

[0009] The application is in breeding drought-resistant cotton varieties with high single boll weight.

[0010] By implementing the technical solution of the present invention, the following beneficial effects can be achieved: 1. The method for evaluating the overall drought resistance grading system of cotton provided by the present invention combines the phenotypic conditions of F2 individual plants at the flowering and boll-opening stages and the yield traits, and can use the overall drought resistance grading method to evaluate the drought resistance of a breeding population. Compared with the prior art, the operation is simple, the workload and calculation amount of trait investigation are greatly reduced, and breeding materials with excellent drought resistance and yield can be obtained quickly and efficiently.

[0011] 2. The present invention divides the drought resistance grades of the BC1F2 breeding segregation population by using the flowering and boll stage, which is the most susceptible to drought stress, and the boll opening stage, which most directly reflects the effect of drought stress on cotton yield. At the same time, single boll weight index related to yield after drought stress is selected for significance analysis with each grade, and the drought resistance index is analyzed in BC1F2. 2:3 In the population stage, the drought resistance of extreme materials was verified in two ways: grade selection and single boll re-selection. The single boll weight after drought stress converted the drought resistance grade from intuitive phenotype to specific data. At the same time, the yield level of related materials was evaluated to a certain extent. The extreme drought-resistant material strains were further multiplied and breeding materials with excellent drought resistance and yield were screened. The present invention provides a method for quickly and efficiently screening breeding materials with excellent drought resistance and yield in the breeding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a diagram of the evaluation criteria for the grading system.

[0013] Among them, A is the overall phenotype of the materials divided by grade at the flowering and boll stage; B is the overall phenotype of the materials divided by grade at the boll opening stage; C is the yellowing of leaves at each grade at the flowering and boll opening stage, and CK represents the normal control; D is the normal distribution diagram of the single boll weight of individual plants investigated at the boll opening stage after drought stress at the flowering and boll opening stage; SBW represents the single boll weight, and the ordinate represents the frequency. The three parental materials marked in the figure are K85-174, SY321 and LL84, respectively; E is the significant correlation analysis between the grade division results and the single boll weight data of individual plants after drought stress, and the significance analysis was performed using one-way analysis of variance, *** represents extremely significant differences, ** represents very significant differences, * represents significant differences, and ns represents insignificant differences.

[0014] Figure 2 The chart shows the changes in cotton boll size at different levels during the flowering and boll-opening stages under normal and drought treatments.

[0015] Figure A shows the comparison of cotton boll sizes of various grades at the flowering and boll stage, and Figure B shows the comparison of cotton boll sizes of various grades at the boll opening stage. CK is the normal treatment, DS is the drought stress treatment, and the cotton bolls were all taken from the middle and lower parts.

[0016] Figure 3 Venn diagram for graded extreme mixed pool and single bell re-divided extreme mixed pool.

[0017] Figure A shows the Venn diagram of drought-resistant (RD) ponds, and Figure B shows the Venn diagram of drought-sensitive (SD) ponds. DJ is the abbreviation of the grade, and SBW is the abbreviation of single boll weight.

[0018] Figure 4 This is a significant difference analysis diagram for extreme mixed pools divided by grade and single bell weight.

[0019] Figure A shows a box plot of significant differences between DJ_RD and DJ_SD of extreme mixed pools selected for grade classification and the drought resistance measurement value D; Figure B shows a box plot of significant differences between SBW_RD and SBW_SD of extreme mixed pools selected for single boll weight classification and the drought resistance measurement value D; Figure C shows a box plot of significant differences between DJ_RD and DJ_SD of extreme mixed pools selected for grade classification and the drought resistance coefficient DCSBW; Figure D shows a box plot of significant differences between SBW_RD and SBW_SD of extreme mixed pools selected for single boll weight classification and the drought resistance coefficient DCSBW; T test was used for significance analysis, *** represents extremely significant difference, and ** represents very significant difference. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The drought-resistant materials "Shiyuan 321" and "Kui 85-174" used in this application are currently recognized varieties. The general public can obtain the "Shiyuan 321" material through the Shijiazhuang Academy of Agriculture and Forestry Sciences and the "Kui 85-174" material through the Xinjiang Bayinguoleng Mongol Autonomous Prefecture Agricultural Science Research Institute. "Shiyuan 321" and "Kui 85-174" in this application are cotton varieties obtained by this research group in the early stage. They have been disclosed in the article "Identification of Physiological Indicators of Cotton Drought and Salt Tolerance and Isolation of Drought and Salt Tolerance Related cDNA Fragments" on June 1, 2007, and are preserved in the College of Agriculture of Xinjiang Agricultural University. The general public can also obtain them through the College of Agriculture of Xinjiang Agricultural University.

[0022] The drought-resistant material Shiyuan 321 and the drought-sensitive material Kui 85-174 used in the implementation experiment of the present invention are the extremely drought-resistant progeny material LL84 selected from the drought-resistant RIL (recombinant inbred lines, RILs) population of the parents, and are parent materials obtained by common means in the common variety breeding in the field.

[0023] Unless otherwise specified in the following embodiments, the technical means used are conventional means well known to those skilled in the art.

[0024] Example 1: Establishing an overall drought resistance grading system 1. Test materials The population material used for establishing the drought resistance system of the present invention is a large-scale secondary segregation backcross population (Back In 2022, the BC1F2 population was planted and data surveyed at the cotton breeding base of Xinjiang Agricultural University, 3rd Company, 144th Regiment, Shawan County, Tacheng District, Xinjiang. In 2023, the BC1F2 population was planted at the Jiushenghe cotton breeding base in Liuhudi Town, Manas County, Changji City, Xinjiang. 2:3Planting and data survey of the population. All relevant materials are preserved by the cotton innovation team of Xinjiang Agricultural University.

[0025] 2. Drought stress test of BC1F2 population The present invention was carried out in 2022 at the cotton breeding base of Xinjiang Agricultural University, 3rd Company, 144th Regiment, Shawan County, Tacheng District, Xinjiang. The material was planted using sub-film drip irrigation technology, with a plant spacing of 10 cm, and artificial planting in a wide and narrow row mode of three double rows. The experimental treatment adopted drought stress during the flowering and boll period in the field. On July 1, water was controlled in the single-plant planting area of ​​2409 BC1F2 populations. In order to enhance the phenotypic differences, the irrigation water was reduced three times compared with the normal irrigation of the field (the irrigation cycle was 8-10 days, and the average irrigation volume was about 28 m 3 / mu), and rewatering was carried out on August 5, and then normal irrigation was carried out with the field. At the same time, a drought resistance grading system was established based on the phenotypic changes during drought stress at the flowering and boll stage and the changes in yield traits at the boll opening stage, and the overall drought resistance of BC1F2 individual plants was evaluated.

[0026] 3. Establish an overall drought resistance classification system The present invention observes the overall phenotype of the BC1F2 group single plant materials at the flowering and boll stage and the boll opening stage, and finds that after the group single plant materials are subjected to drought stress, the leaves of each plant wilt to varying degrees when the daytime temperature is high, and recover to varying degrees when the night temperature is low, and the difference in this change is large. At the same time, there are also manifestations such as the color of the leaves changes from green to dark green and gradually turns yellow, some bottom leaves and upper cotton buds fall off, the boll opening period of some plants is advanced, and the boll opening rate is low.

[0027] Therefore, the grading criteria for drought resistance of BC1F2 populations were developed for the flowering and boll stage and the boll opening stage. The representative single plants, leaves, and bolls of each grade are shown in the attached Figure 1 Figures A, B, C and Appendix Figure 2 As shown, the survey was conducted at both the flowering and boll stage and the boll opening stage. The specific division is based on the following: (1) The classification standard of drought resistance at the flowering and boll stage focuses on leaves and buds Level 1: The leaves are basically not yellow, but dark green. The leaves at the lower nodes are not yellow. The leaves as a whole will wilt slightly in hot weather. The wilting will be relieved after overnight. The boll rate is slightly affected, which is reflected in the shedding of a small amount of cotton buds. Level 2: 25-50% of the leaves turn yellow near the petiole 1 / 3, the leaves at the lower node turn yellow but do not fall off, a small number of leaves dry up, most of the wilting leaves will ease after overnight, and the cotton bud boll rate is moderately affected; Level 3: 50-75% of the leaves turn yellow near the 2 / 3 of the petiole, 1-2 leaves fall off at the lower node, the upper cotton buds dry up and fall off, a small number of wilted leaves will be relieved after overnight, and the boll formation rate is severely affected; Level 4: All leaves turn yellow, more than 2 leaves fall off at the lower nodes, leaves wilt severely, and the wilt does not improve overnight, which has a serious impact on the boll setting rate.

[0028] (2) The classification standard of drought resistance during the boll opening period focuses on the boll opening rate Level 1: 8-9 or above bells; Level 2: 6-7 bells; Level 3: 4-5 bells of cotton wool; Level 4: 3 or fewer bells.

[0029] Based on cotton yield factors, the final drought resistance grade focuses on the drought resistance grade at the boll opening stage. The calculation formula is: final drought resistance grade = drought resistance grade at the flowering and boll opening stage * 40% + drought resistance grade at the boll opening stage * 60%. The resulting grades are all retained as integers.

[0030] The drought resistance of 2409 BC1F2 plants was evaluated using this drought resistance classification standard. The results showed that among the 2409 BC1F2 plants, 37 were at level 1, 188 were at level 2, 1284 were at level 3, and 900 were at level 4. At the same time, there were significant differences in the boll sizes of different levels, see Appendix. Figure 2 In addition to phenotypic observation, this study also selected the method of measuring the weight of a single boll per plant to directly reflect the difference in yield: at the boll opening stage, the middle bolls of 2409 BC1F2 plants were harvested and the weight of the single boll was measured, see Appendix Figure 1 As shown in D, the normal distribution histogram shows that the boll weight of BC1F2 plants after drought stress presents a normal distribution, and there is a super-parental inheritance phenomenon; the single boll weight data and the BC1F2 plant grade classification results were selected for significant correlation analysis, and the results are shown in the attached Figure 1 As shown in Figure E, it was found that there were significant differences in the size of single boll among the grades, which indicated that each grade was significantly associated with the size of single boll after drought stress.

[0031] Example 2: BC1F 2:3 Comprehensive identification of drought resistance of populations with multiple traits 1. BC1F 2:3 Comprehensive evaluation of drought resistance of populations with multiple traits The present invention was carried out in 2023 at the Jiushenghe cotton breeding base in Liuhudi Town, Manas County, Changji City, Xinjiang, and the BC1F 2:3All plants were planted artificially according to the strain line, with one-meter plot, one film and six materials, divided into two replicates. Normal and drought stress treatments were respectively carried out on July 7 at the flowering and boll stage. Compared with normal irrigation in the field, the plants were irrigated twice less. Rewatering treatment was carried out on July 29, and then normal irrigation was carried out with the field. Drought resistance-related traits were investigated at the boll opening stage.

[0032] Due to BC1F 2:3 The instability of the population and the small number of strains, uniform growth of the materials to be investigated were selected, at least 3 strains were selected, and the trait indicators to be investigated included plant height (PH), height at the node of the first fruit branch (HNFFB), fruit branch number (FBN), effective fruit branch number (EFBN), boll number (BN), effective boll number (EBN), etc. The investigation method refers to the "Cotton Germplasm Resource Description Specification and Data Standard" formulated by Du Xiongming et al. The three middle bolls on each single plant in each strain were manually collected, and the single boll weight (SBW) was calculated using a 1 / 1000 electronic balance.

[0033] 2. Data Analysis Microsoft Excel 2021 software was used to summarize and organize the data of each group. IBMSPSS Statistics for Windows, version 21.0 was used for descriptive statistics, principal component analysis, paired T test, etc. Microscientific Information Online (https: / / www.bioinformatics.com.cn / ) was used for normal distribution and visualization, and GraphPad Prism version 9.0.1 for Windows was used for T test box plot drawing. The drought resistance coefficient DC value, comprehensive drought resistance coefficient CDC value and drought resistance measure D value were used to analyze the BC1F 2:3 The comprehensive drought resistance of the group was evaluated. Finally, Adobe Illustrator CS6 was used to beautify the puzzle.

[0034] The relevant calculation formula is calculated according to the calculation method of Sun Fenglei (Sun Fenglei, Qu Yanying, Chen Quanjia, et al. Comprehensive evaluation and grey correlation analysis of cotton drought resistance related indicators [J]. Agricultural Research in Arid Areas. 2019, 37(1): 233-239.) et al.: Drought resistance coefficient:

[0035] Comprehensive drought resistance coefficient:

[0036] Membership function:

[0037] Drought resistance metrics:

[0038] In the above calculation formulas, X d , X w are the measured values ​​of each index of each material under drought stress and normal control, is the average value of this index under drought stress, DI i min ,DI i max is the minimum and maximum value of drought resistance index of each trait; r i is the contribution rate of the ith comprehensive indicator.

[0039] 3. Choice of extreme materials According to the single boll weight and grade classification of the BC1F2 generation individual plants after drought stress, 30 extremely drought-resistant individual plant materials and 30 extremely drought-sensitive individual plant materials were selected to construct an extreme mixed pool, totaling 120 extreme materials. 2:3 The drought resistance of each strain was evaluated in the first generation. The drought resistance-related traits of cotton, such as plant height, height of the first fruiting branch, number of bolls, number of effective bolls, number of fruiting branches, number of effective branches, and single boll weight, were investigated at the boll-opening stage. The drought resistance coefficient DC value and drought resistance measurement value D value were calculated, and the correlation and accuracy of the drought resistance classification system and the comprehensive drought resistance identification were compared. Figure 3 As shown in the figure, the selected materials were analyzed using the Venn diagram and found that there was a 26.7% (8 / 30) overlap between the drought-resistant materials selected based on grade and the drought-resistant materials selected based on the size of the single boll after drought stress, and a 50% (15 / 30) overlap between the drought-sensitive materials selected based on grade and the drought-sensitive materials selected based on the size of the single boll after drought stress, which indicates the discreteness of the BC1F2 population. At the same time, the deviation between the materials selected by the two methods is mainly reflected in the size of the single boll of the plant itself. Therefore, in order to screen materials with excellent drought resistance and yield, a combination of the two may be required.

[0040] 4. Descriptive Statistics At the boll opening stage, the traits of plant height, height of the first fruit branch, number of bolls, number of effective bolls, number of fruit branches, number of effective branches and single boll weight of these extreme materials were investigated, and descriptive statistical analysis was performed. The results are shown in Table 1. It was found that among the extreme materials selected by grade, the coefficient of variation of the number of effective bolls in the normal treatment group and the drought stress treatment group was the largest, which was 34.43% and 46.25% respectively, and the coefficient of variation of the number of bolls was second, which was 34.31% and 44.50% respectively, indicating that the discrete degree of the number of effective bolls and bolls of these materials was large and was most affected by drought stress. The paired T test found that the number of bolls, number of effective bolls, number of fruit branches, number of effective branches and single boll weight showed very significant differences between the normal and drought treatment groups, indicating that these traits were seriously affected by drought stress and were significantly related to cotton drought resistance.

[0041] Table 1: BC1F 2:3 Group level selection Extreme material Descriptive statistics

[0042] Note: T in the table refers to paired T test, ** represents very significant difference, * represents significant difference, no * represents no significant difference.

[0043] As shown in Table 2, among the extreme materials selected by single boll weight after drought stress, the coefficient of variation of the number of bolls in the normal treatment group was the largest, which was 38.39%, and the coefficient of variation of the number of effective bolls was the second largest, which was 37.63%. The coefficient of variation of the number of effective bolls in the drought stress treatment group was the largest, which was 52.02%, and the coefficient of variation of the number of bolls was the second largest, which was 48.79%. This shows that the dispersion of the number of effective bolls and bolls of these materials is large, and they are most affected by drought stress. The paired T test found that plant height, number of bolls, number of effective bolls, number of fruit branches, number of effective branches and single boll weight were all very significantly different between the normal and drought treatment groups, indicating that these traits were severely affected by drought stress and were significantly related to cotton drought resistance. These results are very similar to the descriptive statistical results of extreme materials selected by grade.

[0044] Table 2: BC1F 2:3 Descriptive statistics of extreme materials for single-bell reselection in population

[0045] Note: T in the table refers to paired T test, ** represents very significant difference, * represents significant difference, no * represents no significant difference.

[0046] Among the extreme materials selected under the two conditions, the coefficients of variation of the boll number and the effective boll number after drought stress were the largest, indicating that the impact of drought stress on the boll setting rate of cotton is indeed huge, which also indirectly explains the significance of focusing on the boll opening period in the drought resistance grade classification system.

[0047] 5. Comprehensive drought resistance evaluation and verification grading system The drought resistance coefficient DC value and drought resistance measure D value of the 120 selected extreme materials were calculated to evaluate the comprehensive drought resistance of these materials. The drought resistance coefficient DCSBW and drought resistance measure D value of single boll weight of the extreme materials selected by the two methods were analyzed for significant differences. The results are shown in the attached Figure 4 As shown in the figure, the original drought resistance results of the extreme materials selected by grade classification and the extreme materials selected by single boll weight after drought stress were consistent with the drought resistance results obtained by comprehensive drought resistance evaluation, and there was a very significant difference between the drought-resistant mixed pool and the drought-sensitive mixed pool. These results verified the drought resistance of the BC1F2 population, and also proved the authenticity and reliability of using the drought resistance grade classification system to identify the BC1F2 population. In addition, investigating the size of the single boll weight after drought stress is also a key step in the system to screen breeding materials with excellent drought resistance and yield.

[0048] Example 3: Breeding of excellent drought-resistant breeding materials Based on this overall drought resistance classification method, we further propagated the extreme drought resistance materials and investigated their characteristics. As a result, we screened out 4 breeding materials with good phenotypic consistency, strong drought resistance, and excellent yield-related indicators in the BC1F4 generation. The maximum lint percentage under normal planting was 48.91%, and the maximum single boll weight was 6.77g, and the difference was small after drought stress. These materials provide excellent germplasm resources for the cotton breeding field.

[0049] Table 3: Descriptive statistics of the selected excellent materials

[0050] In summary, the present invention selected the flowering and boll stage, which is the most susceptible to drought stress, and the boll opening stage, which is the most intuitive stage for reflecting the effect of drought stress on cotton yield, to classify the drought resistance levels of the BC1F2 breeding segregation population. At the same time, the single boll weight index related to yield after drought stress was selected for significance analysis with each level, and the drought resistance index of the BC1F2 breeding segregation population was analyzed. 2:3 In the population stage, the drought resistance of extreme materials was verified in two ways: grade selection and single boll reselection. The single boll reselection after drought stress converted the drought resistance grade from intuitive phenotype to specific data. At the same time, the yield level of related materials was evaluated to a certain extent. Combined with grade selection, extreme drought-resistant material strains were selected for further generation and expansion, so that breeding materials with excellent drought resistance and yield could be screened. The present invention provides a method for quickly and efficiently screening breeding materials with excellent drought resistance and yield in the breeding process.

[0051] The above implementation modes are only for illustrating the technical concept and features of the present invention in a specific scenario. The purpose is to enable people who need this technology to understand the content of the present invention and implement it. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for evaluating the overall drought resistance classification system of cotton, characterized in that: The evaluation method specifically includes the following steps: S1. Determine the cotton varieties to be evaluated; S2. Under drought stress treatment and control conditions, the flowering and boll opening period indexes of the selected cotton varieties were measured; S3. According to the individual plant, leaf, and boll conditions of the selected cotton plants in step S2, the drought resistance grade at the flowering and boll stage is obtained; S4. According to the cotton boll opening situation of the selected cotton plants in step S2., the drought resistance grade during the cotton boll opening period is obtained; S5. Calculate the final drought resistance grade according to the drought resistance grade at the flowering and boll stage obtained in step S3 and the drought resistance grade at the boll opening stage obtained in step S4, the final drought resistance grade = drought resistance grade at the flowering and boll stage * 40% + drought resistance grade at the boll opening stage * 60%, and the result grades are retained as integers; S6. Evaluate the drought resistance grade according to the final drought resistance grade obtained in step S5, and screen materials with excellent drought resistance and yield based on the single boll weight index.

2. The method for evaluating the overall drought resistance of cotton according to claim 1, characterized in that: The evaluation criteria for drought resistance grade at flowering and bolling stage in step S3 of the evaluation method are as follows: Level 1: The leaves are basically not yellow, but dark green. The leaves at the lower nodes are not yellow. The leaves as a whole will wilt slightly in hot weather. The wilting will be relieved after overnight. The boll rate is slightly affected, which is reflected in the shedding of a small amount of cotton buds. Level 2: 25-50% of the leaves turn yellow near the petiole 1 / 3, the leaves at the lower node turn yellow but do not fall off, a small number of leaves dry up, most of the wilting leaves will ease after overnight, and the cotton bud boll rate is moderately affected; Level 3: 50-75% of the leaves turn yellow near the 2 / 3 of the petiole, 1-2 leaves fall off at the lower node, the upper cotton buds dry up and fall off, a small number of wilted leaves will be relieved after overnight, and the boll formation rate is severely affected; Level 4: All leaves turn yellow, more than 2 leaves fall off at the lower nodes, leaves wilt severely, and the wilt does not improve overnight, which has a serious impact on the boll setting rate.

3. The method for evaluating the overall drought resistance of cotton according to claim 1, characterized in that: The drought resistance rating standard of step S4 during the boll opening period in the evaluation method is as follows: Level 1: 8-9 or above bells; Level 2: 6-7 bells; Level 3: 4-5 bells of cotton wool; Level 4: 3 or fewer bells.

4. Application of a cotton overall drought resistance grading system evaluation method as described in any one of claims 1 to 3 in cotton breeding.

5. Application of the method for evaluating the overall drought resistance of cotton as claimed in claim 4 in cotton breeding, characterized in that: The application is in breeding drought-resistant cotton varieties with high single boll weight.

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