Method for evaluating field drought resistance and drought-resistant gene effect of transgenic maize

Abstract

The invention discloses a method for evaluating field drought resistance and drought-resistant gene effect of transgenic maize, belongs to the technical field of transgenic maize breeding, and provides a method for evaluating field drought resistance and drought-resistant gene effect of transgenic maize, which comprises the following steps: sowing transgenic maize seeds and non-transgenic maize seeds, watering seedling emergence water, performing drought stress treatment and normal irrigation treatment in groups, and detecting the yield index of the to-be-detected corn material; calculating the drought resistance index of the transgenic corn, and evaluating the field drought resistance of the transgenic corn. Calculating the drought resistance index of the non-transgenic maize, calculating the drought resistance improvement coefficient of the transgenic maize by combining the drought resistance index of the transgenic maize, and evaluating the drought resistance gene effect of the transgenic maize; and grading according to the drought resistance improvement coefficient of the transgenic corn, and selecting the drought-resistant transgenic corn. Carrying out whole-growth-period insufficient irrigation drought stress treatment, detecting yield indexes, carrying out data processing, and evaluating the drought resistance of the transgenic maize according to numerical values.

Description

Technical Field

[0001] The invention belongs to the technical field of transgenic corn breeding, and in particular relates to a method for evaluating drought resistance of transgenic corn in the field and assessing drought resistance gene effects. Background Art

[0002] As an abiotic stress factor, drought is one of the most serious natural disasters that restricts crop growth and development. Since 2000, the frequency and duration of global droughts have increased, resulting in an increase in global food production losses year by year. To fundamentally solve this problem, on the one hand, we must strengthen the rational development and utilization of limited water resources, and on the other hand, we must start with crop germplasm improvement and cultivate and screen crop varieties that are drought-resistant and high-yielding. It can be seen that screening and innovating drought-resistant corn germplasm and cultivating drought-resistant and water-saving corn varieties have become the main ways to ensure food demand.

[0003] Since the 1990s, crop breeding has entered the third breakthrough stage of the organic combination of biotechnology and conventional technology. Modern molecular breeding technology with molecular markers and transgenic technology as the core has greatly improved the efficiency and accuracy of breeding. Conventional breeding requires 7 to 8 generations to select breeding materials, while modern technology can shorten it to 2 to 3 generations, and the breeding cycle is shortened to 1 / 4 to 1 / 3 of the original, achieving rapid, targeted and efficient breeding of new crop varieties with improved systems. In addition to significantly improving breeding efficiency, the combination of transgenic technology and conventional technology is also playing an important role in increasing agricultural product output, breaking through resource constraints, and alleviating ecological deterioration. In the past 10 years, my country's corn production has seen a slowdown in yield growth, and coupled with the impact of global climate change, corn breeding has entered a climbing stage. The comprehensive use of various advanced breeding technologies to coordinate the improvement of related traits such as yield, disease and insect resistance, stress resistance, and efficient nutrient utilization is the main direction of future development in the field of corn breeding, and it is also an important choice to break through the bottleneck of corn breeding technology. Modern biotechnology can achieve the targeted transfer of stress-resistant genes, showing great advantages in improving traits that are difficult to achieve with conventional technologies in the short term. The combination of transgenic technology and conventional breeding technology has effectively led to scientific and technological progress in the field of corn breeding.

[0004] Many studies have shown that drought-resistant breeding of maize is an effective way to improve the drought resistance of varieties and reduce losses caused by drought. The basic premise of drought-resistant breeding is the need for excellent drought-resistant germplasm resources. Conventional improvement of maize drought resistance is difficult because the heritability of yield is low even under good environmental conditions, and the uncertainty of water supply makes the heritability of yield even lower; many studies have shown that maize drought resistance is a complex quantitative inheritance controlled by multiple genes, and hundreds of QTLs and SNP sites related to drought resistance have been detected. In recent years, with the development of molecular biology, transgenic technology, linkage analysis, association analysis, transcriptome analysis, proteome analysis and gene editing technology have provided more direct, effective and accurate methods for genetic improvement of drought resistance. Molecular marker-assisted selection and transgenic technology provide new technical means to solve the problem of drought resistance in maize, and transgenic technology and conventional breeding methods are organically combined to provide a new technical solution for drought-resistant breeding of maize. Scientists have successfully used functional genomics technology and methods to find a large number of genes expressed under drought stress, and have also cloned some genes that regulate drought resistance in corn. They have introduced them into corn plants through transgenic technology, creating new drought-resistant transgenic corn materials with important breeding application value, and applying them to transgenic corn drought-resistant breeding.

[0005] Identification of drought tolerance and evaluation of gene effects of transgenic corn in the field are key steps in evaluating and breeding new drought-tolerant transgenic corn germplasm. At present, there are few reports on the research methods of field drought tolerance screening, identification and gene effect evaluation of transgenic corn at home and abroad. The specific methods used mainly include indoor germination identification method and potted identification method, and the indicators used are mostly physiological indicators. However, the damage caused by drought to corn involves all stages of corn growth and development, and ultimately manifests itself in a decrease in yield. The quality of various indicators in the identification method should be based on yield. At present, there is no ideal method for the identification and evaluation of drought tolerance and drought resistance gene effect evaluation of transgenic corn in the field. Therefore, it is urgent to strengthen research in this area. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a method for evaluating drought resistance of transgenic corn in the field and evaluating the effect of drought resistance genes. Transgenic corn and non-transgenic corn plants are taken as the objects, and drought stress treatment with insufficient irrigation during the whole growth period and normal irrigation treatment are adopted to detect the yield index significantly related to drought resistance. After data processing, the drought resistance of transgenic corn is evaluated according to the numerical value, so as to achieve the purpose of establishing an objective and accurate method for evaluating drought resistance of transgenic corn in the field and evaluating the effect of drought resistance genes.

[0007] To achieve the above object, the present invention provides a method for evaluating drought resistance of transgenic corn in the field and assessing the effect of drought resistance genes, comprising the following steps:

[0008] (1) sowing transgenic corn seeds and non-transgenic corn seeds, watering them for germination, and obtaining transgenic corn plants and non-transgenic corn plants;

[0009] (2) Dividing the transgenic corn plants of step (1) into two groups, one group undergoing drought stress treatment throughout the entire growth period, and the other group undergoing normal irrigation treatment throughout the entire growth period, to obtain drought stress transgenic corn test materials and normal irrigation transgenic corn test materials; dividing the non-transgenic corn plants of step (1) into two groups, one group undergoing drought stress treatment throughout the entire growth period, and the other group undergoing normal irrigation treatment throughout the entire growth period, to obtain drought stress non-transgenic corn test materials and normal irrigation non-transgenic corn test materials;

[0010] (3) detecting the yield index of the drought-stressed transgenic corn test material, the normally irrigated transgenic corn test material, the drought-stressed non-transgenic corn test material, and the normally irrigated non-transgenic corn test material in step (2);

[0011] (4) calculating the drought resistance index of the transgenic corn according to the yield indexes of the drought-stressed transgenic corn test material, the normally irrigated transgenic corn test material, the drought-stressed non-transgenic corn test material, and the normally irrigated non-transgenic corn test material in step (3), and evaluating the drought resistance of the transgenic corn in the field;

[0012] (5) calculating the drought resistance index of the non-transgenic corn according to the yield index of the drought-stressed transgenic corn test material, the normally irrigated transgenic corn test material, the drought-stressed non-transgenic corn test material, and the normally irrigated non-transgenic corn test material in step (3); calculating the drought resistance improvement coefficient of the transgenic corn in combination with the drought resistance index of the transgenic corn in step (4), and evaluating the drought resistance gene effect of the transgenic corn;

[0013] (6) Classifying the transgenic corn according to the improved coefficient of drought resistance in step (5) to select drought-resistant transgenic corn.

[0014] Preferably, the non-transgenic corn seeds in step (1) are transgenic recipients of transgenic corn seeds, the sowing density in step (1) is 4000 to 5000 plants per mu, the sowing is carried out in a land area with an annual natural rainfall of less than 100 mm during the whole growth period of corn, and the sowing is carried out in a film-covered planting method.

[0015] Preferably, the method of watering the seedlings in step (1) is drip irrigation, the time of watering the seedlings is within 24 hours after sowing, and the irrigation amount of the seedling water is 45-55m 3 / mu.

[0016] Preferably, the whole growth period in step (2) is the jointing stage, the trumpet stage, the tasseling stage, the flowering stage, the early filling stage, the middle filling stage and the late filling stage; the drought stress treatment in step (2) is the irrigation amount of 22.5-27.5m3 in the jointing stage. 3 / mu, the irrigation amount during the trumpet period is 22.5~27.5m 3 / mu, the irrigation amount during the male stage is 22.5~27.5m 3 / mu, the irrigation amount during the flowering period is 22.5~27.5m 3 / mu, the initial irrigation volume is 22.5~27.5m 3 / mu, the irrigation volume in the middle of grouting is 22.5~27.5m 3 / mu, the irrigation volume in the late grouting period is 22.5~27.5m 3 / mu; the normal irrigation treatment in step (2) is 45-55m 3 / mu, the irrigation amount during the trumpet period is 45~55m 3 / mu, the irrigation amount during the male stage is 45-55m 3 / mu, the irrigation amount during the flowering period is 45-55m 3 / mu, the initial irrigation volume is 45~55m 3 / mu, the irrigation volume in the middle of grouting is 45~55m 3 / mu, the irrigation volume in the late grouting period is 45~55m 3 / mu.

[0017] Preferably, the yield index in step (3) is the grain yield of the transgenic corn test material under drought stress, the grain yield of the transgenic corn test material under normal irrigation, the average grain yield of the transgenic corn test material under normal irrigation and the non-transgenic corn test material under normal irrigation, and the average grain yield of the transgenic corn test material under drought stress and the non-transgenic corn test material under drought stress.

[0018] Preferably, the drought resistance index calculation formula of the transgenic corn in step (4) is:

[0019] Drought resistance index of transgenic corn = (grain yield of transgenic corn tested materials under drought stress / grain yield of transgenic corn tested materials under normal irrigation) / (average grain yield of transgenic corn tested materials under drought stress and non-transgenic corn tested materials under drought stress / average grain yield of transgenic corn tested materials under normal irrigation and non-transgenic corn tested materials under normal irrigation).

[0020] Preferably, the calculation formula for the drought resistance index of the non-transgenic corn in step (5) is:

[0021] Drought resistance index of non-transgenic corn = (grain yield of non-transgenic corn tested materials under drought stress / grain yield of non-transgenic corn tested materials under normal irrigation) / (average grain yield of transgenic corn tested materials under drought stress and non-transgenic corn tested materials under drought stress / average grain yield of transgenic corn tested materials under normal irrigation and non-transgenic corn tested materials under normal irrigation);

[0022] The calculation formula for the drought resistance improvement coefficient of the transgenic corn in step (5) is:

[0023] The improvement coefficient of drought resistance of transgenic corn = drought resistance index of transgenic corn / drought resistance index of non-transgenic corn.

[0024] Preferably, the classification standard in step (6) is:

[0025] The drought resistance improvement coefficient of transgenic corn is ≤1.00, the drought resistance improvement level is 0, and the drought resistance of transgenic corn is no better than that of non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is 1.00<1.25, the drought resistance improvement level is 1, and the drought resistance of transgenic corn is slightly better than that of non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is 1.25<1.50, the drought resistance improvement level is 2, and the drought resistance of transgenic corn is moderately better than that of non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is 1.50<1.75, the drought resistance improvement level is 3, and the drought resistance of transgenic corn is significantly better than that of non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is 1.75<2.00, the drought resistance improvement level is 4, and the drought resistance of transgenic corn is significantly better than that of non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is>2.00, the drought resistance improvement level is 5, and the drought resistance of transgenic corn is greatly better than that of non-transgenic corn.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] The present invention takes transgenic corn and non-transgenic corn plants as the objects, adopts under-irrigation drought stress treatment and normal irrigation treatment during the whole growth period, detects the yield index significantly related to drought resistance, evaluates the drought resistance of transgenic corn according to the numerical value after data processing, and establishes an objective and accurate method for evaluating drought resistance of transgenic corn in the field and evaluating the effect of drought resistance genes.

[0028] (1) The present invention subjects transgenic corn and non-transgenic corn to drought stress throughout their growth period, conducts a detailed study on the changes in yield indicators that are highly correlated with drought resistance of transgenic corn and non-transgenic corn after drought stress throughout their growth period, establishes a grading standard for drought resistance evaluation, and establishes a method for screening transgenic corn for field drought resistance identification and evaluation and drought resistance gene effect assessment.

[0029] (2) The present invention uses mature transgenic corn plants as evaluation objects, and the test materials are easy to obtain. A large number of transgenic plants can be evaluated at the same time, which is highly efficient.

[0030] (3) The method of the present invention has the characteristics of a wide range of applications. The evaluation criteria are quantified, which is more objective and accurate. It is suitable for screening corn germplasm with different degrees of improved drought resistance compared with non-transgenic corn.

[0031] (4) The present invention uses a scheme of under-irrigation and drought stress for transgenic corn throughout its growth period, thereby avoiding the problem of inconsistent stress periods and stress levels among materials at different maturity stages. Materials at different maturity stages can be put together for screening and identification, thus avoiding the difficulty of separate identification of materials at different maturity stages. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Example 1

[0038] 1. Test materials.

[0039] 7 non-transgenic corn recipient conventional inbred lines (hereinafter referred to as recipients) and 54 transgenic corn materials. Among them, 5 transgenic line materials and 1 receptor carrying the LOS5 gene, including f1-f5 and Zheng 58 (receptor 5), were provided by China Agricultural University; 8 transgenic line materials and 1 receptor carrying the ABP9 gene, including (s1-s8) and Qi 319 (receptor 7), were provided by the Institute of Biotechnology, Chinese Academy of Agricultural Sciences; 20 transgenic line materials and 3 receptors carrying the TsVPI gene, including a1-a9, Chang 7-2 (receptor 1), b1-b4, 478 (receptor 2), d1-d7, Luyuan 92 (receptor 3), 17 transgenic line materials and 1 receptor carrying the betA gene, including p1-p17 and 7922 (receptor 6), were provided by Shandong University; 4 transgenic line materials and 1 receptor carrying the CBL and PLD2 genes, including e1-e4 and Zong 31 (receptor 4), were provided by the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences.

[0040] 2. Test method.

[0041] The method for screening drought-resistant transgenic corn and evaluating the effect of drought-resistant genes is as follows:

[0042] 2.1 Corn seed selection.

[0043] Select well-developed transgenic corn seeds and non-transgenic corn receptor control seeds that need to be identified, and each test seed is required to be uniformly full.

[0044] 2.2 Seeding of transgenic corn and recipients.

[0045] During the whole growth period of corn, the corn is sown in the land area with annual natural precipitation less than 100 mm, covered with film, and each material is planted in one plot, with a diameter of 12 m 2 , random block arrangement, three replicates, sowing density of 4500 plants / mu. Within 24 hours after sowing, 50m 3 / mu of irrigation, drip irrigation for seedling emergence, so that the moisture content of 0-50cm soil layer reaches 80%±5% of field water holding capacity.

[0046] 2.3 Drought stress treatment and normal irrigation treatment of transgenic corn and recipients.

[0047] Drought stress treatment (dry land): The amount of irrigation for seven times between jointing stage and harvest was half of the irrigation amount of the water area, see Table 1 for details.

[0048] Normal irrigation treatment (water field): fully irrigate throughout the growth period. The specific irrigation time and amount are shown in Table 1.

[0049] Table 1 Irrigation schemes and irrigation volumes for different treatments

[0050]

[0051] 2.4 Detection of genetically modified corn and receptor indicators.

[0052] The morphological indices of all the tested materials were measured: plant height, ear height, tasseling stage, pollen shedding stage, and silking stage. The number of harvested plants and ears was measured at harvest, and the yield indices were measured after harvest: ear length, ear diameter, number of grains per row, number of grains per row, grain yield per plot, and grain moisture content per plot. Among them, some indices were used to evaluate varieties.

[0053] 2.5 Evaluation of drought tolerance of transgenic corn.

[0054] The drought resistance index (field drought resistance) of the transgenic corn material to be tested was calculated using the following formula:

[0055] Drought resistance index of tested transgenic corn material = (grain yield of tested material under drought stress treatment / grain yield of tested material under normal irrigation treatment) / (average grain yield of all materials in dry land / average grain yield of all materials in water land). The water content of all grains is 14%.

[0056] The drought resistance index of transgenic maize recipients was calculated using the following formula:

[0057] Transgenic corn recipient drought resistance index = (recipient drought stress treatment grain yield / recipient normal irrigation treatment grain yield) / (all materials dry land average grain yield / all materials water land average grain yield). Among them, the water content of all grains is 14%.

[0058] The drought resistance improvement coefficient (drought resistance gene effect) of the tested transgenic corn was calculated using the following formula:

[0059] The coefficient of improvement of drought resistance of transgenic corn = drought resistance index of the transgenic corn material to be tested / drought resistance index of the transgenic corn recipient.

[0060] Transgenic corn is graded according to its improved drought tolerance coefficient. The grading standards are detailed in Table 2.

[0061] Table 2 Drought resistance gene effect standard

[0062]

[0063]

[0064] 2.6 The transgenic corns to be tested were graded according to the grading standards described in Table 2, and transgenic corns with significantly or greatly improved drought tolerance were selected as needed.

[0065] 3. Results and analysis.

[0066] Table 3 Evaluation results of drought tolerance and drought resistance effect of 54 tested transgenic corn samples

[0067]

[0068]

[0069] As can be seen from Table 3, according to this grading standard, among the 54 tested transgenic materials, 2 materials had drought tolerance improved by 0 level compared with the recipient, 9 materials had improved by 1 level, 16 materials had improved by 2 levels, 4 materials had improved by 3 levels, 2 materials had improved by 4 levels, and 21 materials had improved by 5 levels. Among them, 52 transgenic corn materials had improved drought tolerance compared with the recipient, accounting for 96% of all tested materials, and 23 materials had significantly improved drought tolerance (above level 4), accounting for 43% of all tested materials.

[0070] According to the classification results in Table 3, transgenic corn materials with significantly improved or greatly improved drought tolerance are selected for breeding as needed to cultivate new drought-resistant transgenic corn varieties.

[0071] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for evaluating drought resistance of transgenic corn in the field and assessing the effect of drought resistance genes, characterized in that: The following steps are involved: (1) sowing transgenic corn seeds and non-transgenic corn seeds, watering them for germination, and obtaining transgenic corn plants and non-transgenic corn plants; (2) Dividing the transgenic corn plants of step (1) into two groups, one group undergoing drought stress treatment throughout the entire growth period, and the other group undergoing normal irrigation treatment throughout the entire growth period, to obtain drought stress transgenic corn test materials and normal irrigation transgenic corn test materials; dividing the non-transgenic corn plants of step (1) into two groups, one group undergoing drought stress treatment throughout the entire growth period, and the other group undergoing normal irrigation treatment throughout the entire growth period, to obtain drought stress non-transgenic corn test materials and normal irrigation non-transgenic corn test materials; (3) detecting the yield index of the drought-stressed transgenic corn test material, the normally irrigated transgenic corn test material, the drought-stressed non-transgenic corn test material, and the normally irrigated non-transgenic corn test material in step (2); (4) calculating the drought resistance index of the transgenic corn according to the yield indexes of the drought-stressed transgenic corn test material, the normally irrigated transgenic corn test material, the drought-stressed non-transgenic corn test material, and the normally irrigated non-transgenic corn test material in step (3), and evaluating the drought resistance of the transgenic corn in the field; (5) calculating the drought resistance index of the non-transgenic corn according to the yield index of the drought-stressed transgenic corn test material, the normally irrigated transgenic corn test material, the drought-stressed non-transgenic corn test material, and the normally irrigated non-transgenic corn test material in step (3); calculating the drought resistance improvement coefficient of the transgenic corn in combination with the drought resistance index of the transgenic corn in step (4), and evaluating the drought resistance gene effect of the transgenic corn; (6) Classifying the transgenic corn according to the improved coefficient of drought resistance in step (5) to select drought-resistant transgenic corn.

2. The method according to claim 1, characterized in that: The non-transgenic corn seeds in step (1) are transgenic recipients of transgenic corn seeds. The sowing density in step (1) is 4,000 to 5,000 plants per mu. The sowing is carried out in land areas where the annual natural rainfall during the whole growth period of corn is less than 100 mm. The sowing is carried out in a film-covered planting method.

3. The method according to claim 1, characterized in that: The method of watering the seedlings in step (1) is drip irrigation, the time of watering the seedlings is within 24 hours after sowing, and the irrigation amount of the seedling water is 45-55m 3 / mu.

4. The method according to claim 1, characterized in that: The whole growth period in step (2) is the jointing stage, the trumpet stage, the tasseling stage, the flowering stage, the early filling stage, the middle filling stage and the late filling stage; the drought stress treatment in step (2) is the irrigation amount of 22.5-27.5m3 in the jointing stage. 3 / mu, the irrigation amount during the trumpet period is 22.5~27.5m 3 / mu, the irrigation amount during the male stage is 22.5~27.5m 3 / mu, the irrigation amount during the flowering period is 22.5~27.5m 3 / mu, the initial irrigation volume is 22.5~27.5m 3 / mu, the irrigation volume in the middle of grouting is 22.5~27.5m 3 / mu, the irrigation volume in the late grouting period is 22.5~27.5m 3 / mu; the normal irrigation treatment in step (2) is 45-55m 3 / mu, the irrigation amount during the trumpet period is 45~55m 3 / mu, the irrigation amount during the male stage is 45-55m 3 / mu, the irrigation amount during the flowering period is 45-55m 3 / mu, the initial irrigation volume is 45~55m 3 / mu, the irrigation volume in the middle of grouting is 45~55m 3 / mu, the irrigation volume in the late grouting period is 45~55m 3 / mu.

5. The method according to claim 1, characterized in that: The yield index in step (3) is the grain yield of the transgenic corn test material under drought stress, the grain yield of the transgenic corn test material under normal irrigation, the average grain yield of the transgenic corn test material under normal irrigation and the non-transgenic corn test material under normal irrigation, and the average grain yield of the transgenic corn test material under drought stress and the non-transgenic corn test material under drought stress.

6. The method according to claim 1, characterized in that: The calculation formula for the drought resistance index of the transgenic corn in step (4) is: Drought resistance index of transgenic corn = (grain yield of transgenic corn tested materials under drought stress / grain yield of transgenic corn tested materials under normal irrigation) / (average grain yield of transgenic corn tested materials under drought stress and non-transgenic corn tested materials under drought stress / average grain yield of transgenic corn tested materials under normal irrigation and non-transgenic corn tested materials under normal irrigation).

7. The method according to claim 1, characterized in that: The calculation formula for the drought resistance index of the non-transgenic corn in step (5) is: Drought resistance index of non-transgenic corn = (grain yield of non-transgenic corn tested materials under drought stress / grain yield of non-transgenic corn tested materials under normal irrigation) / (average grain yield of transgenic corn tested materials under drought stress and non-transgenic corn tested materials under drought stress / average grain yield of transgenic corn tested materials under normal irrigation and non-transgenic corn tested materials under normal irrigation); The calculation formula for the drought resistance improvement coefficient of the transgenic corn in step (5) is: The improvement coefficient of drought resistance of transgenic corn = drought resistance index of transgenic corn / drought resistance index of non-transgenic corn.

8. The method according to claim 1, characterized in that: The classification criteria in step (6) are: The drought resistance improvement coefficient of transgenic corn is ≤1.00, the drought resistance improvement level is 0, and the drought resistance of transgenic corn is not improved compared with non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is 1.00<1.25, the drought resistance improvement level is 1, and the drought resistance of transgenic corn is slightly improved compared with non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is 1.25<1.50, the drought resistance improvement level is 2, and the drought resistance of transgenic corn is moderately improved compared with non-transgenic corn; the drought resistance improvement coefficient of transgenic corn is 1.50<1.75, the drought resistance improvement level is 3, and the drought resistance of transgenic corn is significantly improved compared with non-transgenic corn; 1.75<GMO corn drought resistance improvement coefficient≤2.00, drought resistance improvement level is 4, GMO corn has significantly improved drought resistance than non-GMO corn; The improved drought resistance coefficient of transgenic corn is >2.00, and the improved drought resistance level is level 5. The drought resistance of transgenic corn is significantly improved compared to non-transgenic corn.

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