Method for identifying and evaluating cold resistance of wheat at booting stage

Abstract

The invention discloses a method for identifying and evaluating cold resistance of wheat in booting stage, which relates to the technical field of wheat biology, and is technically characterized by comprising the following steps: selecting wheat varieties with obvious late spring coldness resistance difference for potted planting; carrying out different low-temperature treatments on the key growth stages of wheat in spring by utilizing an artificial climate chamber; measuring the dead stem rate, the frozen ear rate, the relative maturing rate and the thousand seed weight of the wheat under the low-temperature treatment; the indexes are comprehensively compared and analyzed to finally determine the optimal identification condition capable of effectively distinguishing the cold resistance difference between the varieties; and further verifying the effectiveness of the identification conditions, and carrying out resistance grade division. The invention provides a method for identifying and evaluating the cold resistance of wheat at the booting stage, which discovers that the cold resistance of wheat at the booting stage can be rapidly and accurately identified by measuring the ear freezing rate through low-temperature treatment at-2 DEG C / 48 hours at the booting stage of wheat, and further provides a method for identifying and evaluating the cold resistance of wheat at the booting stage. And the identification result can objectively reflect the real performance of the wheat variety resistance.

Description

Technical Field

[0001] The invention relates to the technical field of wheat biology, and more specifically to a method for identifying and evaluating the cold resistance of wheat at the heading stage. Background Art

[0002] Against the backdrop of global warming, winter temperatures are rising and the growth period of wheat is advanced, making wheat more vulnerable to low temperatures in spring, where late spring cold may occur, and the risk of frost damage is also increasing. Once late spring cold occurs, it will pose a serious threat to wheat growth, generally resulting in a 30% to 50% reduction in wheat production, and even a total crop failure in severe years. From 2001 to 2021, the frequency of late spring cold in my country's main wheat-producing areas was as high as 40%. The late spring cold in 2013 caused the affected area of ​​wheat to reach 41.8% of the total sown area, and some high-quality varieties were almost completely lost, thus withdrawing from the ranks of dominant varieties. Late spring cold seriously threatens the safe production of wheat and the stable development of agriculture. At present, agricultural measures to deal with late spring cold are ineffective. Cultivating and promoting new late spring cold-resistant wheat varieties is the most economical, scientific, simple and effective way to reduce yield losses. Accurately identifying and effectively distinguishing the late spring cold resistance levels among different varieties is particularly critical for the selection and approval of new wheat varieties.

[0003] Domestic and foreign scholars have conducted a series of studies on the identification of wheat resistance to late spring cold, but most of these studies are based on cultivation physiology or disaster reduction and avoidance, focusing only on the harm caused by a certain low temperature to wheat, and not considering the reliability of the evaluation method from the variety level. At present, the existing identification methods are mainly concentrated in the jointing stage of wheat, and most of them measure indirect indicators such as physiological and biochemical, and yield. These methods also have many problems, such as inconsistent identification methods, arbitrary low-temperature treatment conditions, and many, chaotic, and difficult-to-measure indicators. These problems make it difficult for existing methods to effectively evaluate the genetic characteristics of wheat varieties resistant to late spring cold. In field production, the most common manifestation of wheat encountering late spring cold is frozen ears, including dumb ears, half-truncated ears, and missing grains. In contrast, using the frozen ear rate as a grading standard for the degree of frost damage can more intuitively reflect the actual damage to wheat.

[0004] Therefore, the present invention takes the frozen ear rate as an evaluation index, aiming to provide a method for identifying and evaluating the cold resistance of wheat at the heading stage, so as to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a method for identifying and evaluating the cold resistance of wheat at the heading stage. The present invention uses an artificial climate chamber to carry out different low-temperature treatments for the key stages of wheat growth in spring; the dead stem rate, frozen ear rate, relative fruit set rate and thousand-grain weight of wheat under low-temperature treatment are measured; by conducting a comprehensive comparative analysis of the indicators, the optimal identification conditions that can effectively distinguish the differences in cold resistance between varieties are finally determined; the effectiveness of the identification conditions is further verified, and resistance grades are divided, and on this basis, a method for identifying and evaluating the cold resistance of wheat at the heading stage is proposed.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: A method for identifying and evaluating the cold resistance of wheat at the heading stage, comprising the following steps:

[0007] (1) Preliminary exploration of identification conditions: Wheat varieties with obvious differences in late spring cold resistance in field production were selected for potted planting. Different temperatures were treated in an artificial climate chamber at different development stages, and the freezing ear rate was used as an evaluation index to analyze the significance of resistance differences among varieties under different treatment conditions. The optimal treatment conditions for wheat cold resistance using the freezing ear rate as an evaluation index were preliminarily obtained.

[0008] (2) Re-exploration and optimization of identification conditions: Based on the results of previous studies, we further improved the condition screening test from three aspects. First, we expanded the types and quantities of experimental materials to improve sample diversity; second, we added identification indicators to strive to more comprehensively evaluate the experimental results; third, we expanded the treatment period to explore the impact of different developmental stages of wheat on the experimental results. Specifically, among the wheat varieties with obvious differences in late spring cold resistance, we continued to add winter wheat varieties and spring wheat varieties with different resistance performances, subjected wheat at different developmental stages to different low temperature treatments, and conducted investigations on dead stem rate, frozen ear rate, relative fruit set rate and thousand-grain weight. Through comprehensive comparative analysis of the indicators, we finally obtained the optimal identification conditions that can effectively distinguish the resistance differences between wheat varieties.

[0009] (3) Verification of identification conditions and classification of resistance: Using the optimal identification conditions determined above, a natural population consisting of 161 wheat germplasm materials was identified for cold resistance. A significant difference test and cluster analysis were performed on the large amount of identification data obtained. Based on the results of the cluster analysis, a scientific and practical classification standard for the evaluation of cold resistance of wheat at the booting stage was formulated.

[0010] The present invention is further configured as follows: the optimal identification conditions for effectively distinguishing the differences in cold resistance between wheat varieties in steps (1) and (2) are consistent: using the frozen ear rate as the identification index, the heading period, and the treatment at -2°C / 48h, the identification effect is most ideal, which is the optimal treatment condition.

[0011] The present invention is further configured as follows: in step (3), the cold resistance evaluation levels of wheat at the heading stage are: strong, relatively strong, medium, weak, and relatively weak.

[0012] The present invention is further configured to: adopt a potted planting method and use an artificial climate chamber to carry out cold resistance identification of wheat at the booting stage

[0013] In summary, the present invention has the following beneficial effects:

[0014] The present invention clarifies the treatment period, evaluation index and treatment intensity of wheat late spring cold resistance identification, and on this basis establishes a method for identifying and evaluating wheat cold resistance at the heading stage. The method can correctly, comprehensively and quickly evaluate the cold resistance of wheat varieties at the heading stage from a genetic perspective, and the evaluation indexes used are not only simple and easy to operate, but also have the feasibility and effectiveness of carrying out large-scale variety identification work. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the process of identifying cold resistance of wheat at the heading stage according to an embodiment of the present invention;

[0016] Figure 2 Schematic diagram of the frost damage symptoms of wheat at the heading stage in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following is combined with Figure 1-2 The present invention is described in further detail.

[0018] Embodiment: A method for evaluating the cold resistance of wheat at the heading stage comprises the following contents:

[0019] A preliminary study on the identification conditions of S1

[0020] In order to clarify the suitable treatment conditions for the identification of late spring cold resistance of wheat, the frozen ear rate was used as an evaluation index. The study was conducted at the Hefei Experimental Base of Anhui Academy of Agricultural Sciences in 2021-2022. Six wheat varieties with obvious differences in late spring cold resistance, including Jimai 22 (strong), Yannong 19 (medium), Zhengzhou 8329 (weak), Wanmai 50 (weak), Zhengmai 366 (weak) and Xi'an 8 (weak), were selected for treatment at different developmental stages and different temperatures (Table 1). The frozen ear rate was used as an evaluation index to analyze the significance of resistance differences among varieties under different treatment conditions. The results showed that no frozen ear was observed in different treatments at the jointing stage and heading stage. At -4℃ in the booting stage, the dead stem rate of the six varieties was 80% to 100% for 12h and 24h treatments, indicating that the -4℃ treatment exceeded the low temperature tolerance range of wheat at the booting stage.

[0021] At -3℃ and -2℃ treatments during the booting stage, the main symptoms of freezing damage were dumb ears, white ears and half-truncated ears ( Figure 2), all were recorded as frozen ears in statistical analysis. Taking the frozen ear rate as the evaluation index, the resistance performance trends of the six varieties under different treatments were relatively consistent, all of which were strong for Jimai 22; Yannong 19, Zhengzhou 8329, Wanmai 50, and Zhengmai 366 were relatively weak; Xi'an 8 was weak. It shows that the frozen ear rate can be used as an evaluation index during the booting period to intuitively reflect the freezing situation of wheat, and the identification and evaluation effect is good. The frozen ear rate of the six varieties under different treatments is shown in Table 2. The change trend of the frozen ear rate of the six varieties under different treatments is relatively consistent, and all increase with the extension of treatment time and the decrease of temperature. Under different treatments, the coefficient of variation of the frozen ear rate of the six varieties is: –3℃ / 24h(0.45)<–3℃ / 18h(0.46)<–2℃ / 24h(0.61)<–2℃ / 724h(0.66)<–2℃ / 48h(0.85). It shows that under the treatment of -2℃ / 48h, the difference in resistance to frozen ear rate among varieties is the most significant, followed by -2℃ / 72h. In summary, with the frozen ear rate as the evaluation index, -2℃ / 48h and -2℃ / 72h are both suitable treatment conditions for the booting stage. Based on the principle of more efficient and faster identification, -2℃ / 48h was selected as the identification condition for the booting stage.

[0022] Due to the outbreak of a virus disease in potted wheat this year, the plants were stunted and the ear formation rate was low, so the test results need to be further verified.

[0023] Table 1 Low temperature treatment design table

[0024]

[0025] Table 2 Frozen ear rate of six varieties under different treatments

[0026]

[0027]

[0028] Re-exploration and optimization of S2 identification conditions

[0029] Based on the exploration of the wheat ear freezing rate, this embodiment continues to optimize and improve the identification method in 2022-2023 by adding test materials and identification indicators. Based on the lack of strong and medium resistance materials in the original six test materials, three materials, Huaimai 22 (strong), Xinong 511 (medium) and Anke 1303 (medium), were added according to production performance. In addition, in order to verify the relationship between late spring cold resistance and winter-spring characteristics of wheat, two spring varieties, Yangmai 20 and Ningmai 13, were added.

[0030] This year, 14 different treatments were set up (Table 3). After the treatments, the dead stem rate, frozen ear rate, fruit set rate and thousand-grain weight were investigated, and the results were rounded to two decimal places.

[0031] Dead stem rate = number of dead stems / total number of stems surveyed;

[0032] Frozen ear rate = number of frozen ears / total number of surveyed ears * 100%;

[0033] Average number of grains per ear = total number of grains per marked main stem per pot / total number of ears per marked main stem * 100%;

[0034] Relative seed setting rate = average number of grains per ear in treatment / average number of grains per ear in control;

[0035] Thousand-grain weight = total grain weight of the marked main stem per pot / total number of grains on the marked main stem*1000.

[0036] Table 3 Low temperature treatment design table

[0037]

[0038] 1. Survey results of dead stem rate

[0039] At the jointing stage, under the treatment of -2℃ and -3℃ for different durations, the dead stem rate was 0.00, and the resistance difference between varieties could not be distinguished. At the booting stage, under the treatment of -2℃ for different durations, the dead stem rate of varieties was 0.00, and the resistance difference between varieties could not be distinguished; under the treatment of -3℃ for different durations, the dead stem rate of varieties reached more than 0.80, and the resistance difference between varieties was not obvious. At the heading stage, under -2℃ / 24h and -2℃ / 48h, the dead stem rate was 0.00, and the resistance difference between varieties could not be distinguished. At the flowering stage, under -2℃ / 24h and -2℃ / 48h, the dead stem rate was 0.00, and the resistance difference between varieties could not be distinguished.

[0040] 2. Thousand-grain weight survey results

[0041] As shown in Tables 4 and 5, at the jointing stage, booting stage, heading stage and flowering stage, the changes in thousand-grain weight among varieties were significantly different under each treatment compared with the control. Among them, at the heading stage at -2℃ / 24h, the thousand-grain weight of each variety had the largest change range and the difference between varieties was the most significant.

[0042] At the jointing stage, the low temperature treatment at -2℃ for 24h reduced the thousand-grain weight by 0.81% compared with the control; the treatment for 48h reduced the thousand-grain weight by 6.64% compared with the control; and the treatment for 72h increased the thousand-grain weight by 4.61% compared with the control, showing a trend of first decreasing and then increasing with the extension of the treatment time. According to the increase and decrease of thousand-grain weight, the varieties were ranked. At -2℃ / 24h, the increase was Huaimai 22 < Yannong 19 < Yangmai 20 < Zhengzhou 8329 < Ningmai 13 < Jimai 22 < Xinong 511; the decrease was Wanmai 50 < Zhengmai 366 < Anke 1303. At -2℃ / 48h, the increase was Yangmai 20 < Huaimai 22 < Jimai 22; the decrease was Yannong 19 < Ningmai 13 < Xinong 511 < Zhengzhou 8329 < Zhengmai 366 < Anke 1303 < Wanmai 50. At -2℃ / 72h, the increase was Zhengzhou 8329 < Huaimai 22 < Anke 1303 < Zhengmai 366 < Yangmai 20 < Yannong 19 < Ningmai 13 < Jimai 22; the decrease was Xinong 511 < Wanmai 50. It can be seen that under the treatment of different lengths of -2℃, the change trend of the thousand-grain weight of each variety did not show obvious regularity and consistency. At -3℃, the low temperature treatment for 18h increased the thousand-grain weight by 1.96% compared with the control; the treatment for 24h increased the thousand-grain weight by 14.19% compared with the control. The thousand-grain weight showed an increasing trend with the extension of the treatment time, but the change trend of the thousand-grain weight of the varieties under different treatments also lacked obvious regularity and consistency.

[0043] In addition, it can be seen from Table 5 that there is no obvious regularity and consistency in the changes of thousand-grain weight during the booting stage, heading stage and flowering stage. This is because the thousand-grain weight is sensitive to the environment and is easily affected by a variety of factors. It is not directly determined by low temperature and freezing damage. The measurement process is relatively cumbersome and prone to large errors, which leads to the difficulty of showing obvious regularity in the change trend of thousand-grain weight under different low temperature treatment conditions. In summary, the thousand-grain weight is not suitable as an indicator for evaluating the strength of resistance to late spring cold.

[0044] Table 4 Changes in thousand-grain weight of different varieties under various treatments at jointing stage

[0045]

[0046] Table 5 Changes in thousand-grain weight of different varieties under various treatments at booting stage, heading stage and flowering stage

[0047]

[0048] Table 6 Fruit setting rate of different varieties under different treatment periods

[0049]

[0050]

[0051] 3. Fruit setting rate survey results

[0052] The results of the fruit set rate survey under different treatments at different stages are shown in Table 6. By comparing the fruit set rates of varieties under different treatments at the same developmental stage, it was found that under the treatments of -2℃ / 24h, -2℃ / 48h, -2℃ / 72h, -3℃ / 18h and -3℃ / 24h at the jointing stage, the standard deviations were small, 0.06, 0.04, 0.07, 0.10 and 0.13, respectively, and the resistance differences between varieties could not be effectively distinguished. Under the treatments of -2℃ / 24h and -2℃ / 48h at the heading stage, the standard deviations were small, 0.04 and 0.11, respectively, and the resistance differences between varieties could not be effectively distinguished. Under the treatments of -2℃ / 24h and -2℃ / 48h at the flowering stage, the standard deviations were small, 0.10 and 0.09, respectively, and the resistance differences between varieties could not be effectively distinguished. At the booting stage, the range of variation of the fruit setting rate under -2℃ / 24h was relatively small, ranging from 0.64 to 0.99, and the standard deviation was 0.14, which was too low to effectively distinguish the resistance differences among varieties. Compared with -2℃ / 24h, the variation range and standard deviation of the relative fruit setting rate of 11 varieties under -2℃ / 48h and -2℃ / 72h increased, indicating that the resistance and susceptibility differences of the 11 varieties under -2℃ / 48h and -2℃ / 72h were more significant. Compared with -2℃ / 48h and -2℃ / 72h, the standard deviation under -2℃ / 72h treatment was larger, but the mean and variation range of fruit setting rate were similar. Considering the high efficiency of the treatment and the accommodation capacity of the artificial climate chamber, -2℃ / 48h was the most suitable treatment condition because the time was shorter.

[0053] Based on the above results, it can be determined that with the fruit set rate as the evaluation index, the most suitable treatment condition is -2℃ / 48h during the booting stage, which can effectively identify the late spring cold resistance of wheat varieties.

[0054] 4. Survey results on frozen ear rate

[0055] At the jointing stage, no frozen ear occurred under different treatments of -2℃ and -3℃, and the frozen ear rate was 0.00%. At the booting stage, at -2℃, the frozen ear was obvious; at -3℃, the dead stem rate of the variety was as high as 90%. Due to the serious dead stems, no frozen ear investigation was conducted, which was inconsistent with the previous research results that there was no dead stem at -3℃, indicating that the viral disease that broke out in 2021-2022 had a great impact on the test results. At the heading stage, at -2℃ / 24h and -2℃ / 48h, no frozen ear occurred, and the frozen ear rate was 0.00%. At the flowering stage, at -2℃ / 24h and -2℃ / 48h, no frozen ear occurred, and the frozen ear rate was 0.00%. It was verified again that the booting stage is the appropriate identification period for frozen ears.

[0056] An in-depth analysis of the frozen ear rate of each variety under different treatments of -2℃ during the booting stage was conducted (Table 7). At -2℃ / 24h, the average frozen ear rate of 11 varieties was as low as 13.32%, with a range of 1.00% to 38.46%. The difference in resistance to frozen ear rate among varieties was small, indicating that the low temperature treatment of -2℃ / 24h during the booting stage was not conducive to identifying the difference in resistance levels among different varieties. Compared with -2℃ / 24h, the change range and standard deviation of the frozen ear rate of 11 varieties at -2℃ / 48h and -2℃ / 72h increased, indicating that the resistance and susceptibility differences of the 11 varieties at -2℃ / 48h and -2℃ / 72h were more significant. Compared with -2℃ / 48h and -2℃ / 72h, the variation range and standard deviation of frozen ear rate under -2℃ / 72h treatment were larger, indicating that -2℃ / 72h had stronger discrimination ability. However, considering the high efficiency of treatment and the accommodation capacity of artificial climate chamber, -2℃ / 48h was the shorter time and the most suitable treatment condition.

[0057] Based on the above results, it can be determined that with the frozen ear rate as the evaluation index, the most suitable treatment condition is -2℃ / 48h during the heading period, which can effectively identify the late spring cold resistance of wheat varieties.

[0058] Table 7 Frozen ear rate of varieties under different treatments at -2℃ during booting stage

[0059]

[0060] 5. Comparison of fruit setting rate and frozen ear rate at booting stage

[0061] At the booting stage, under the treatment of -2℃ / 48h, both the frozen ear rate and the fruit setting rate can effectively distinguish the resistance differences between varieties, and the results of variety resistance identification tend to be consistent, and both can be used as indicators for evaluating wheat late spring cold resistance. However, the frozen ear rate is a direct indicator, and the fruit setting rate is an indirect indicator; the frozen ear rate can directly reflect the freezing of wheat ears, while the fruit setting rate is affected by many factors and cannot reflect frost damage alone; the frozen ear rate is intuitive and easy to investigate, while the fruit setting rate is complex to determine and has large errors. Therefore, at the booting stage, it is more appropriate to use the frozen ear rate as an evaluation indicator for wheat late spring cold resistance.

[0062] Based on the above results, it can be determined that at the booting stage, -2℃ / 48h is the most suitable treatment condition with the frozen ear rate as the evaluation index, which can effectively identify the late spring cold resistance of wheat varieties.

[0063] S3 identification condition verification and resistance grade classification

[0064] 1. Verification of identification conditions

[0065] In order to further verify the scientific rationality of the optimal identification conditions at the booting stage, the study used the booting stage -2℃ / 48h to identify the late spring cold resistance of 161 wheat varieties (lines) in the Huanghuai wheat region in 2023-2024. The results showed that the frozen ear rate among the 161 wheat varieties (lines) was significantly different, with a large variation range of 0.00% to 78.00% (Table 8). This shows that the treatment condition of -2℃ / 48h with the frozen ear rate as the evaluation index at the booting stage can well distinguish the differences in late spring cold resistance among varieties, and the identification conditions are scientific and reasonable.

[0066] Table 8 Frozen ear rate of 161 wheat varieties

[0067]

[0068]

[0069] 2. Resistance level classification

[0070] Cluster analysis was further used to classify the 161 wheat varieties into five categories: extremely strong, strong, medium, weak, and extremely weak. Based on the classification results, a preliminary evaluation standard for late spring cold resistance in wheat at the heading stage was established (Table 9).

[0071] Table 9 Evaluation criteria for late spring cold resistance in wheat at the booting stage

[0072]

[0073] Conclusion: The identification method of the present invention is to plant wheat in pots, use an artificial climate chamber to simulate a low temperature environment, and treat wheat at the heading stage at -2℃ / 48h. By investigating the frozen ear rate, large-scale, rapid, and accurate identification of wheat cold resistance can be achieved. The present invention is the first to create the conditions for the occurrence and identification period of wheat frozen ear. The frozen ear rate is more intuitive, accurate, and easy to measure than traditional physiological and biochemical indicators. The artificial climate chamber is used to simulate a low temperature environment, which can overcome the limitations of general experiments on instruments, equipment, and sites, and achieve the same environment and high-efficiency identification.

[0074] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for identifying and evaluating the cold resistance of wheat at the heading stage, characterized in that: The following steps are involved: (1) Select wheat varieties with obvious differences in late spring cold resistance in field production for potted planting; (2) Using artificial climate chambers, different low temperature treatments were carried out for the key stages of wheat growth in spring: jointing, booting, heading, and flowering; (3) Determine the dead stem rate, frozen ear rate, relative fruit set rate and thousand-grain weight of wheat varieties under low temperature treatment at different development stages; (4) Through comprehensive comparative analysis of the measured indicators, the optimal identification indicators that can effectively distinguish the differences in cold resistance among varieties, as well as the optimal identification period and low temperature treatment intensity that are adapted to them, are finally determined; (5) Further verification of identification conditions and classification of resistance levels, that is, using the optimal identification conditions determined above, cold resistance identification work was carried out on a natural population consisting of 161 wheat germplasm materials, and a large amount of identification data obtained was tested for significance of differences and cluster analysis. Based on the results of cluster analysis, a scientific and practical standard for the evaluation of cold resistance of wheat at the heading stage was formulated, thereby providing a clear and quantitative reference basis for the resistance evaluation of wheat varieties and facilitating the selection and promotion of excellent varieties in agricultural production.

2. The method for identifying and evaluating the cold resistance of wheat at the heading stage according to claim 1, characterized in that: The nine wheat varieties with obvious differences in late spring cold resistance in field production in step (1) are Jimai 22 (strong), Huaimai 22 (strong), Yannong 19 (medium), Xinong 511 (medium), Anke 1303 (medium), Zhengzhou 8329 (weak), Wanmai 50 (weak), Zhengmai 366 (weak), and Xi'an No. 8 (weak).

3. The method for identifying and evaluating the cold resistance of wheat at the heading stage according to claim 1, characterized in that: The potted planting method in step (1) is as follows: the soil used is the topsoil of the field, impurities and stones are screened out before the soil is potted to ensure uniform soil particles, a cylindrical pot with a diameter of 28 cm and a height of 31 cm is selected, each pot is filled with 15 kg of air-dried soil with sufficient basal fertilizer, and placed in the test field, the sowing period is the appropriate sowing period for local wheat, 15 holes are sown in each pot, 1 seed is sown in each hole, and the seedlings are fixed to 8 plants at the 3-leaf stage, and fertilization is carried out according to conventional field management.

4. The method for identifying and evaluating the cold resistance of wheat at the heading stage according to claim 1, characterized in that: The step (2) is a key stage of wheat growth in spring, the jointing stage is specifically the inter-adherent stage of spikelet differentiation (the remaining number of leaves is 1.5 leaves); the heading stage is when the pulvinus distance between the flag leaf and the second leaf reaches 2 cm to 6 cm; the heading stage is when 80% of the wheat ears extend halfway out of the flag leaf sheath; the flowering stage is the beginning of flowering of wheat, that is, when 80% of the wheat ears have 2-5 small flowers blooming in the middle.

5. The method for identifying and evaluating the cold resistance of wheat at the heading stage according to claim 1, wherein: The optimal identification conditions for effectively distinguishing the differences in cold resistance between varieties in step (4) are: using the frozen ear rate as the identification index, the heading period, and the treatment at -2°C / 48h. The identification effect is most ideal and is the optimal treatment condition.

6. The method for identifying and evaluating the cold resistance of wheat at the heading stage according to claim 1, characterized in that: In the step (5), the cold resistance evaluation grade of wheat at the heading stage is divided into five grades: strong, relatively strong, medium, relatively weak and weak.

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