Corn variety high temperature tolerance performance evaluation method based on multi-reproductive stage accurate identification

Abstract

The application discloses a corn variety high-temperature-resistant performance evaluation method based on multi-growth-stage accurate identification, and comprises the following steps: calculating suitable seeding dates according to the determined growth and development heat requirement of each corn variety, so that each corn variety reaches different growth stages within a certain time; setting a control group and a high-temperature treatment group in each growth period of each corn variety, performing stage high-temperature stress treatment on the high-temperature treatment group, and keeping the rest time consistent with the normal temperature control group; measuring the morphological indexes, physiological indexes and yield traits of corn plants in each high-temperature treatment group and normal temperature control group; based on the measured index data, calculating the total high-temperature-resistant coefficients of each corn variety in different growth periods, then comprehensively evaluating the high-temperature-resistant performances of each corn variety in different growth periods and grading according to the evaluation results. The application realizes accurate and high-throughput identification of the high-temperature-resistant performance of corn in multiple growth stages, and the result is intuitive and has high breeding and cultivation application value.

Description

Technical Field

[0001] This invention relates to the field of maize stress resistance breeding technology, specifically to a method for evaluating the high-temperature resistance performance of maize varieties based on precise identification at multiple growth stages. Background Technology

[0002] Corn is my country's largest grain crop, and its market demand continues to rise with the improvement of people's living standards. The industry has long faced a supply-demand imbalance for corn. At the same time, the trend of global warming is intensifying, with the frequency of extreme heat events increasing from 3.5% to 4.5%, and their duration becoming longer, increasingly highlighting their impact on agricultural production.

[0003] Although maize is a warm-season crop, high-temperature stress significantly inhibits its production. When the ambient temperature exceeds the high-temperature threshold, for every 1°C increase in average temperature, maize grain yield decreases by 7.4%. The Huang-Huai-Hai summer maize region, as my country's core maize-producing area, accounts for about one-third of the country's planting area and yield. In recent years, the occurrence of high temperatures exceeding 35°C during the growing season in this region has significantly advanced, occurring in mid-June to early-July for two consecutive years in 2023 and 2024, lasting for 7-10 days, thus continuously expanding the impact on maize growth, development, and yield formation.

[0004] Promoting heat-resistant maize varieties is the most effective means to resist high-temperature stress and ensure maize production. However, existing technologies for identifying the heat resistance of maize varieties have many shortcomings: First, the identification stage is singular, mostly concentrated in the seedling or flowering stage, which cannot reflect the differences in heat resistance at key growth stages such as ear differentiation and development, pollination and seed setting. Second, planting and identification methods are limited, often using potted plants followed by identification in greenhouses or artificial climate chambers. Due to the limited facility area, it is difficult to conduct accurate identification at multiple stages and with high throughput. Furthermore, the potted model restricts maize root development, causing water and nutrient absorption to be affected by external factors, and failing to effectively utilize the physiological function of the roots to alleviate high-temperature stress through transpiration. In addition, the identification treatment methods are unreasonable. Some studies use heating throughout the entire growth period, which masks the heat resistance performance of maize at specific growth stages and cannot accurately distinguish the differences in heat resistance at different growth stages. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, this application proposes the following technical solution: This application provides a method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages, including: The maize varieties to be evaluated are determined, and the suitable sowing dates for each maize variety are calculated based on the accumulated temperature requirements for growth and development of each variety, so that each maize variety reaches different growth stages within a given time. For each growth stage of each maize variety, a normal temperature control group and a high temperature treatment group were set up. During the corresponding growth stage, the high temperature treatment group was subjected to staged high temperature stress treatment, and the environmental conditions were kept the same as those of the normal temperature control group for the rest of the time. Morphological, physiological, and yield traits of maize plants in each high-temperature treatment group and the normal-temperature control group were measured. Based on the measured data of each index, the total heat tolerance coefficient of each maize variety at different growth stages was calculated. Based on the total high temperature resistance coefficient, the heat resistance of each maize variety at each growth stage is classified, and the high temperature resistance performance of the maize variety to be evaluated is evaluated based on the classification results.

[0006] In one possible implementation, determining the maize variety to be evaluated and calculating the suitable sowing date for each maize variety based on its accumulated temperature requirements for growth and development, so that each maize variety reaches different growth stages within a predetermined time, includes: The required effective accumulated temperature thresholds for each maize variety to be evaluated at each target growth stage from sowing to jointing, small tasseling, large tasseling, flowering, and grain-filling are obtained using the following formula: in, This refers to the effective accumulated temperature threshold required for a maize variety from sowing to the corresponding target growth stage. For the first time in corn growth The average daily temperature of the day, This is the biological lower limit temperature for maize growth. The number of days from sowing to reaching the target growth stage; The predetermined arrival time of each target growth stage is determined, and the theoretical sowing date for each maize variety corresponding to each target growth stage is calculated backwards based on the number of growing days from sowing to reaching the target growth stage. The calculation formula is as follows: ; in, This refers to the predetermined arrival time for each target reproductive period. The theoretical sowing dates for each maize variety and its target growth stage; Based on the field management conditions of the experimental fields and the local climate fluctuations, the theoretical sowing dates were fine-tuned to ensure that each maize variety reached its corresponding growth stages—jointing stage, small trumpet stage, large trumpet stage, flowering stage, and grain-filling stage—accurately at the designated time.

[0007] In one possible implementation, the temperature settings for the high-temperature treatment group are as follows: daytime temperature 35-40℃, heating begins at 7:00 AM, with a temperature increase of 0.5℃ / h from 7:00 AM to 9:00 AM, a temperature increase of 1.0℃ / h from 9:00 AM to 1:00 PM, a temperature decrease of 1.0℃ / h from 1:00 PM to 5:00 PM, a temperature decrease of 0.5℃ / h from 5:00 PM to 7:00 PM, and heating stops at 7:00 PM; nighttime temperature 25-30℃, with a temperature decrease of 0.42℃ / h from 7:05 PM to 6:59 AM the next day; the normal temperature control group maintains a suitable growth temperature throughout, with daytime and nighttime temperatures of 30-35℃ and 20-25℃ respectively, and the humidity and CO2 concentration inside the heating facility remain consistent with the outside environment throughout the day.

[0008] In one possible implementation, the determination of morphological, physiological, and yield traits of maize plants in each high-temperature treatment group and the normal-temperature control group includes: When the maize plants in the high-temperature treatment group and the normal temperature control group entered the flowering period, maize plants with uniform growth were randomly selected, and the leaf area per plant, the length of the main axis of the tassel, the number and average length of the branches of the tassel, the density of spikelets of the tassel, the total amount of pollen shed, the pollen viability, and the pollen germination rate were measured uniformly. When the maize plants in each high-temperature treatment group and the normal-temperature control group entered the silking stage, the selected sample plants were continuously tracked to determine the total number of silks in the female ear and the difference between male and female silks. When the maize plants in each high-temperature treatment group and the normal-temperature control group reached full maturity, the double-ear rate, empty stalk rate, seed setting rate, ear length, effective ear length, ear diameter, cob diameter, number of rows per ear, number of kernels per row, thousand-kernel weight, and yield per plant were measured.

[0009] In one possible implementation, based on the measured data of various indicators, the total heat tolerance coefficient of each maize variety at different growth stages is calculated, including: Based on the measured data of various indicators, correlation analysis was used to identify several indicators that were most correlated with grain yield loss after high temperature stress. The total heat tolerance coefficient of each maize variety at different growth stages was calculated based on the aforementioned multiple indicators.

[0010] In one possible implementation, the formulas for calculating the total heat tolerance coefficient of each maize variety at different growth stages based on the aforementioned multiple indicators are as follows: in, The total high temperature resistance coefficient during the jointing stage. The high-temperature resistance coefficient is calculated using grain yield as an indicator. The high-temperature resistance coefficient is calculated using the length of the main axis of the tassel. The high-temperature resistance coefficient is calculated using the total powder content index. To calculate the high-temperature resistance coefficient using the settling rate index, To calculate the high-temperature tolerance coefficient using the density of male spikelets, The high-temperature resistance coefficient is calculated using the number of filaments during the silk-spinning period. To calculate the heat tolerance coefficient using pollen viability index, The high-temperature resistance coefficient is calculated using the ear length index. To calculate the high temperature resistance coefficient using the thousand-grain weight index, To calculate the high-temperature tolerance coefficient using the effective spike length index, The high-temperature resistance coefficient is calculated using the number of grains per ear index. The total high temperature resistance coefficient during the small trumpet stage. The total high temperature resistance coefficient during the large trumpet stage. The total high temperature tolerance coefficient during the flowering period. This represents the overall high-temperature resistance coefficient during the grouting period.

[0011] In one possible implementation, the heat tolerance of each maize variety at each growth stage is classified according to the total high-temperature tolerance coefficient, and the high-temperature tolerance of the maize variety to be evaluated is evaluated based on the classification results, including: Based on the total high temperature resistance coefficient, the heat resistance of each maize variety at each growth stage is divided into heat-resistant, moderate, and heat-sensitive levels according to the preset threshold standard. Using the growth stage as the horizontal axis and the total high temperature tolerance coefficient for each growth stage as the vertical axis, a spectrum of high temperature resistance periods for each maize variety was plotted. The high-temperature resistance period spectrum is used to evaluate the high-temperature resistance performance of the maize varieties to be evaluated based on the division results.

[0012] In one possible implementation, the high-temperature resistance performance of the maize variety to be evaluated is assessed using the high-temperature resistance time-period spectrum and based on the segmentation results, including: If the maize variety to be evaluated exhibits heat tolerance level throughout all growth stages, then the maize variety to be evaluated will be rated as a high heat tolerance variety throughout all growth stages. If a maize variety to be evaluated only exhibits heat tolerance during a specific growth period, then the maize variety to be evaluated will be rated as a stage-specific heat-tolerant variety. If a maize variety to be evaluated only exhibits heat sensitivity during a specific growth period, then the maize variety to be evaluated will be classified as a periodically heat-sensitive variety. If the maize variety to be evaluated shows a heat-sensitive level throughout all growth stages, then the maize variety to be evaluated will be rated as a heat-sensitive variety throughout all growth stages. When the heat tolerance of the maize variety to be evaluated is inconsistent and there is no obvious pattern in different growth stages, the maize variety to be evaluated is evaluated as a fluctuating variety.

[0013] Compared with the prior art, the beneficial effects of this application are as follows: This application precisely calculates the appropriate sowing date based on the accumulated temperature requirements of maize growth and development, ensuring that each maize variety reaches its target growth stage within the predetermined time. Furthermore, the evaluation is conducted using a field planting model, avoiding the limitations imposed on maize root development by potted cultivation. This makes the maize's growth status more closely resemble actual production scenarios, and the evaluation results accurately reflect the high-temperature tolerance of the varieties in field conditions. Simultaneously, it applies time-phased high-temperature stress treatments at key growth stages such as the jointing stage and the small trumpet stage, overcoming the drawbacks of heating throughout the entire growth period and accurately identifying differences in heat tolerance at different maize growth stages.

[0014] This application sets up a scientifically designed room-temperature control group and a high-temperature treatment group, strictly standardizes the temperature parameters and variation rhythm of high-temperature stress, and ensures the consistency and controllability of treatment conditions. At the same time, the measured indicators cover morphological indicators, physiological indicators and yield traits of maize during flowering, silking and full maturity stages, comprehensively capturing the impact of high-temperature stress on maize growth, development and yield formation. Furthermore, through relevant analysis, indicators highly correlated with yield loss are screened to calculate the total high-temperature tolerance coefficient, making the evaluation basis more scientific and targeted.

[0015] The identification results of this application can provide dual support for maize breeding and cultivation. Breeding researchers can optimize parent combinations and selectively breed heat-resistant maize varieties based on the heat resistance performance of varieties and the characteristics of parents. Maize cultivation researchers can formulate maize variety optimization layout plans by combining regional high temperature occurrence patterns and variety heat resistance characteristics, providing a basis for growers to select varieties scientifically. At the same time, it also provides experimental data and methodological references for the research and development of maize heat-resistant cultivation measures, helping to improve the stress resistance and yield stability of maize production. Attached Figure Description

[0016] Figure 1 A flowchart illustrating a method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages, provided in this application embodiment; Figure 2 A heat resistance classification diagram of different growth stages of various varieties provided for embodiments of this application; Figure 3 High temperature resistance spectra of various varieties at different growth stages provided in the embodiments of this application. Detailed Implementation

[0017] The present solution will now be described in conjunction with the accompanying drawings and specific embodiments.

[0018] Figure 1 A flowchart illustrating a method for evaluating the high-temperature resistance of maize varieties based on precise identification across multiple growth stages, as provided in this application, is shown below. Figure 1 This embodiment provides a method for evaluating the high-temperature resistance of maize varieties based on precise identification across multiple growth stages, comprising: S101, determine the maize varieties to be evaluated, and calculate the suitable sowing date for each maize variety based on the accumulated temperature requirements for growth and development of each variety, so that each maize variety reaches different growth stages within a predetermined time.

[0019] In this embodiment, the required effective accumulated temperature thresholds for each maize variety to be evaluated during each target growth stage from sowing to jointing, small trumpet stage, large trumpet stage, flowering stage, and grain-filling stage are obtained. The calculation formula is as follows: in, This refers to the effective accumulated temperature threshold required for a maize variety from sowing to the corresponding target growth stage. For the first time in corn growth The average daily temperature of the day, This is the biological lower limit temperature for maize growth. To determine the number of growth days from sowing to reaching the target growth stage, the predetermined arrival time of each target growth stage is established. Based on the number of growth days from sowing to reaching the target growth stage, the theoretical sowing date for each maize variety corresponding to each target growth stage is calculated backwards. The calculation formula is as follows: ;in, This refers to the predetermined arrival time for each target reproductive period. To determine the theoretical sowing dates for each maize variety at its target growth stages, fine-tuning was performed based on field management conditions and local climate fluctuations in the experimental fields. This ensured that each maize variety accurately reached its corresponding jointing, small trumpet stage, large trumpet stage, flowering, and grain-filling stages at the designated times. Each maize variety was planted individually, with 2-3 rows planted at equal row spacing (60 cm row spacing, 5 m row length). Plant spacing was calculated based on the recommended density for each variety.

[0020] S102, a normal temperature control group and a high temperature treatment group were set up for each growth stage of each maize variety. During the corresponding growth stage, the high temperature treatment group was subjected to staged high temperature stress treatment, while the environmental conditions were kept the same as those of the normal temperature control group for the rest of the time.

[0021] In this embodiment, a combined identification device with a light transmittance of greater than or equal to 98% and precise temperature and humidity control was built simultaneously for the room temperature control group and the high temperature treatment group. Depending on the number of corn varieties to be evaluated, the device can be built in 36㎡, 72㎡ or 108㎡. The temperature settings for the high-temperature treatment group were as follows: daytime temperature 35-40℃, heating started at 7:00 AM, with a temperature increase of 0.5℃ / h from 7:00 AM to 9:00 AM, a temperature increase of 1.0℃ / h from 9:00 AM to 1:00 PM, a temperature decrease of 1.0℃ / h from 1:00 PM to 5:00 PM, a temperature decrease of 0.5℃ / h from 5:00 PM to 7:00 PM, and heating was stopped at 7:00 PM; nighttime temperature was 25-30℃, with a temperature decrease of 0.42℃ / h from 7:05 PM to 6:59 AM the next day; the normal temperature control group maintained a suitable growth temperature throughout, with daytime and nighttime temperatures of 30-35℃ and 20-25℃ respectively, and the humidity and CO2 concentration inside the heating facility remained consistent with the outside temperature throughout the day.

[0022] S103, morphological indicators, physiological indicators and yield traits of maize plants in each high-temperature treatment group and the normal-temperature control group were measured respectively.

[0023] In this embodiment, when the maize plants in the high-temperature treatment group and the normal-temperature control group entered the flowering stage, maize plants with uniform growth were randomly selected, and the leaf area per plant, the length of the main axis of the tassel, the number and average length of the branches of the tassel, the density of spikelets of the tassel, the total amount of pollen shed, the pollen viability, and the pollen germination rate were uniformly measured. When the maize plants in the high-temperature treatment group and the normal-temperature control group entered the silking stage, the selected sample plants were continuously tracked, and the total number of silks in the female ear and the difference between male and female silks were measured. When the maize plants in the high-temperature treatment group and the normal-temperature control group entered the full maturity stage, the double ear rate, empty stalk rate, seed setting rate, ear length, barren tip length, ear diameter, cob diameter, number of rows per ear, number of kernels per row, thousand-kernel weight, and yield per plant were measured. The effective ear length refers to the difference between the ear length and the barren tip length, and the number of kernels per ear is the product of the number of rows per ear and the number of kernels per row.

[0024] S104, based on the measured data of various indicators, calculate the total high temperature tolerance coefficient of each maize variety at different growth stages.

[0025] In this embodiment, based on the measured data of various indicators, correlation analysis was used to determine several indicators most correlated with grain yield loss after high-temperature stress. The total high-temperature tolerance coefficient for each maize variety at different growth stages was calculated based on these determined indicators. The calculation formula is as follows: in, The total high temperature resistance coefficient during the jointing stage. The high-temperature resistance coefficient is calculated using grain yield as an indicator. The high-temperature resistance coefficient is calculated using the length of the main axis of the tassel. The high-temperature resistance coefficient is calculated using the total powder content index. To calculate the high-temperature resistance coefficient using the settling rate index, To calculate the high-temperature tolerance coefficient using the density of male spikelets, The high-temperature resistance coefficient is calculated using the number of filaments during the silk-spinning period. To calculate the heat tolerance coefficient using pollen viability index, The high-temperature resistance coefficient is calculated using the ear length index. To calculate the high temperature resistance coefficient using the thousand-grain weight index, To calculate the high-temperature tolerance coefficient using the effective spike length index, The high-temperature resistance coefficient is calculated using the number of grains per ear index. The total high temperature resistance coefficient during the small trumpet stage. The total high temperature resistance coefficient during the large trumpet stage. The total high temperature tolerance coefficient during the flowering period. This represents the overall high-temperature resistance coefficient during the grouting period.

[0026] S105 classifies the heat resistance of each maize variety at each growth stage based on the total high temperature resistance coefficient, and evaluates the high temperature resistance performance of the maize varieties to be evaluated based on the classification results.

[0027] In this embodiment, based on the total high-temperature resistance coefficient, the heat resistance of each maize variety at each growth stage is divided into heat-resistant, moderate, and heat-sensitive levels according to a preset threshold standard. A high-temperature resistance time-period spectrum is plotted for each maize variety, with the growth stage as the horizontal axis and the total high-temperature resistance coefficient for each growth stage as the vertical axis. This spectrum visually displays the comprehensive high-temperature resistance performance of each maize variety at different growth stages. The high-temperature resistance performance of the maize variety under evaluation is assessed based on the spectrum and the classification results. If the maize variety exhibits heat resistance at all growth stages, it is rated as a high-heat-resistant variety throughout all growth stages. If the maize variety exhibits heat resistance at only one or a few specific growth stages, it is rated as a heat-resistant variety in a specific stage. If the maize variety exhibits heat sensitivity at only one or a few specific growth stages, it is rated as a heat-sensitive variety in a specific stage. If a maize variety exhibits heat sensitivity throughout all growth stages, it is classified as a heat-sensitive variety across all growth stages. Conversely, if the heat tolerance of a maize variety is inconsistent across different growth stages without a clear pattern, it is classified as a fluctuating variety. Maize cultivation researchers develop variety optimization layout maps based on the heat tolerance performance of different varieties and the recent high-temperature occurrences in the entire region. This provides a basis for crop growers to scientifically select varieties. Maize breeding researchers can optimize parental combinations and cultivate heat-resistant maize varieties based on the comprehensive heat tolerance performance of different varieties and their parental characteristics.

[0028] In this embodiment, 12 widely planted maize varieties were selected: MC121, Denghai 111, Denghai 1717, Denghai 533, Denghai 605, Jingnongke 736, Mingtian 695, Tiantai 619, Wansheng 69, Xianyu 335, Zhengdan 958, and Zhengyuanyu 432. A randomized block design was adopted, with multiple replicates, and the maize was sown in the field in stages.

[0029] See Figure 2 and Figure 3Based on the above screening methods, Zhengdan 958, Zhengyuanyu 432, Wansheng 69, and Tiantai 619 were identified as heat-resistant varieties in the V6 stage. Denghai 1717, MC121, Denghai 605, and Xianyu 335 were identified as heat-sensitive varieties in the V6 stage. Zhengdan 958, Zhengyuanyu 432, Wansheng 69, and Denghai 1717 were identified as heat-resistant varieties in the V9 stage. MC121, Jingnongke 736, Denghai 605, and Xianyu 335 were identified as heat-sensitive varieties in the V9 stage. Zhengdan 958, Zhengyuanyu 432, Denghai 111, and Denghai 1717 were identified as heat-resistant varieties in the V12 stage; Denghai 605, MC121, Xianyu 335, and Tiantai 619 were identified as heat-sensitive varieties in the V12 stage. Zhengdan 958, Jingnongke 736, Mingtian 695, and Zhengyuanyu 432 are heat-resistant varieties in the VT stage; MC121, Denghai 605, Wansheng 69, and Xianyu 335 are heat-sensitive varieties in the VT stage. Zhengdan 958, Wansheng 69, Denghai 1717, and Jingnongke 736 are heat-resistant varieties in the R2 stage; Denghai 111, Xianyu 335, Denghai 605, and Mingtian 695 are heat-sensitive varieties in the R2 stage. Based on the high-temperature resistance spectrum of each variety at different growth stages, Zhengdan 958 is a heat-resistant variety throughout the entire growth period, Zhengyuanyu 432 is a heat-resistant variety in stages, MC121 is a heat-sensitive variety in stages, Denghai 605 and Xianyu 335 are heat-sensitive varieties throughout the entire growth period, and Denghai 1717, Jingnongke 736, Mingtian 695, Tiantai 619, Wansheng 69, and Denghai 111 are fluctuating heat-resistant varieties.

[0030] In this embodiment, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, the simultaneous existence of A and B, or the existence of B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0031] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0032] The above description is merely a specific embodiment of this application. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. The protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A method for evaluating the high-temperature resistance of maize varieties based on precise identification across multiple growth stages, characterized in that, include: The maize varieties to be evaluated are identified, and the suitable planting dates for each variety are calculated based on their accumulated temperature requirements for growth and development. This ensures that each variety reaches its different growth stages within a given timeframe, including: The required effective accumulated temperature thresholds for each maize variety to be evaluated at each target growth stage from sowing to jointing, small tasseling, large tasseling, flowering, and grain-filling are obtained using the following formula: in, This refers to the effective accumulated temperature threshold required for a maize variety from sowing to the corresponding target growth stage. For the first time in corn growth The average daily temperature of the day, This is the biological lower limit temperature for maize growth. The number of days from sowing to reaching the target growth stage; The predetermined arrival time of each target growth stage is determined, and the theoretical sowing date for each maize variety corresponding to each target growth stage is calculated backwards based on the number of growing days from sowing to reaching the target growth stage. The calculation formula is as follows: ； in, This refers to the predetermined arrival time for each target reproductive period. The theoretical sowing dates for each maize variety and its target growth stage; The theoretical sowing date was fine-tuned based on the field management conditions of the experimental field and the local climate fluctuation characteristics to ensure that each maize variety reached the corresponding jointing stage, small trumpet stage, large trumpet stage, flowering stage, and grain-filling stage at the predetermined time. For each growth stage of each maize variety, a normal temperature control group and a high temperature treatment group were set up. During the corresponding growth stage, the high temperature treatment group was subjected to staged high temperature stress treatment, and the environmental conditions were kept the same as those of the normal temperature control group for the rest of the time. Morphological, physiological, and yield traits of maize plants in each high-temperature treatment group and the normal-temperature control group were measured. Based on the measured data of each index, the total heat tolerance coefficient of each maize variety at different growth stages was calculated. Based on the total high temperature resistance coefficient, the heat resistance of each maize variety at each growth stage is classified, and the high temperature resistance performance of the maize variety to be evaluated is evaluated based on the classification results.

2. The method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages as described in claim 1, characterized in that, The temperature settings for the high-temperature treatment group were as follows: daytime temperature 35-40℃, heating started at 7:00 AM, with a temperature increase of 0.5℃ / h from 7:00 AM to 9:00 AM, a temperature increase of 1.0℃ / h from 9:00 AM to 1:00 PM, a temperature decrease of 1.0℃ / h from 1:00 PM to 5:00 PM, a temperature decrease of 0.5℃ / h from 5:00 PM to 7:00 PM, and heating was stopped at 7:00 PM; nighttime temperature was 25-30℃, with a temperature decrease of 0.42℃ / h from 7:05 PM to 6:59 AM the next day; the normal temperature control group maintained a suitable growth temperature throughout, with daytime and nighttime temperatures of 30-35℃ and 20-25℃ respectively, and the humidity and CO2 concentration inside the heating facility remained consistent with the outside temperature throughout the day.

3. The method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages as described in claim 1, characterized in that, The determination of morphological, physiological, and yield traits of maize plants in each high-temperature treatment group and the normal-temperature control group included: When the maize plants in the high-temperature treatment group and the normal temperature control group entered the flowering period, maize plants with uniform growth were randomly selected, and the leaf area per plant, the length of the main axis of the tassel, the number and average length of the branches of the tassel, the density of spikelets of the tassel, the total amount of pollen shed, the pollen viability, and the pollen germination rate were measured uniformly. When the maize plants in each high-temperature treatment group and the normal-temperature control group entered the silking stage, the selected sample plants were continuously tracked to determine the total number of silks in the female ear and the difference between male and female silks. When the maize plants in each high-temperature treatment group and the normal-temperature control group reached full maturity, the double-ear rate, empty stalk rate, seed setting rate, ear length, effective ear length, ear diameter, cob diameter, number of rows per ear, number of kernels per row, thousand-kernel weight, and yield per plant were measured.

4. The method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages as described in claim 1, characterized in that, Based on the measured data of various indicators, the total heat tolerance coefficient of each maize variety at different growth stages was calculated, including: Based on the measured data of various indicators, correlation analysis was used to identify several indicators that were most correlated with grain yield loss after high temperature stress. The total heat tolerance coefficient of each maize variety at different growth stages was calculated based on the aforementioned multiple indicators.

5. The method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages according to claim 4, characterized in that, The formulas for calculating the total heat tolerance coefficient of each maize variety at different growth stages based on the aforementioned multiple indicators are as follows: in, The total high temperature resistance coefficient during the jointing stage. The high-temperature resistance coefficient is calculated using grain yield as an indicator. The high-temperature resistance coefficient is calculated using the length of the main axis of the tassel. The high-temperature resistance coefficient is calculated using the total powder content index. To calculate the high-temperature resistance coefficient using the settling rate index, To calculate the high-temperature tolerance coefficient using the density of male spikelets, The high-temperature resistance coefficient is calculated using the number of filaments during the silk-spinning period. To calculate the heat tolerance coefficient using pollen viability index, The high-temperature resistance coefficient is calculated using the ear length index. To calculate the high temperature resistance coefficient using the thousand-grain weight index, To calculate the high-temperature tolerance coefficient using the effective spike length index, The high-temperature resistance coefficient is calculated using the number of grains per ear index. The total high temperature resistance coefficient during the small trumpet stage. The total high temperature resistance coefficient during the large trumpet stage. The total high temperature tolerance coefficient during the flowering period. This represents the overall high-temperature resistance coefficient during the grouting period.

6. The method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages according to claim 1, characterized in that, Based on the total high-temperature tolerance coefficient, the heat tolerance of each maize variety at each growth stage is classified, and the high-temperature tolerance of the maize variety to be evaluated is assessed based on the classification results, including: Based on the total high temperature resistance coefficient, the heat resistance of each maize variety at each growth stage is divided into heat-resistant, moderate, and heat-sensitive levels according to the preset threshold standard. Using the growth stage as the horizontal axis and the total high temperature tolerance coefficient for each growth stage as the vertical axis, a spectrum of high temperature resistance periods for each maize variety was plotted. The high-temperature resistance period spectrum is used to evaluate the high-temperature resistance performance of the maize varieties to be evaluated based on the division results.

7. The method for evaluating the high-temperature resistance of maize varieties based on precise identification of multiple growth stages according to claim 6, characterized in that, The high-temperature resistance period spectrum and the high-temperature resistance performance of the maize varieties to be evaluated are assessed based on the segmentation results, including: If the maize variety to be evaluated exhibits heat tolerance level throughout all growth stages, then the maize variety to be evaluated will be rated as a high heat tolerance variety throughout all growth stages. If a maize variety to be evaluated only exhibits heat tolerance during a specific growth period, then the maize variety to be evaluated will be rated as a stage-specific heat-tolerant variety. If a maize variety to be evaluated only exhibits heat sensitivity during a specific growth period, then the maize variety to be evaluated will be classified as a periodically heat-sensitive variety. If the maize variety to be evaluated shows a heat-sensitive level throughout all growth stages, then the maize variety to be evaluated will be rated as a heat-sensitive variety throughout all growth stages. When the heat tolerance of the maize variety to be evaluated is inconsistent and there is no obvious pattern in different growth stages, the maize variety to be evaluated is evaluated as a fluctuating variety.

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