A method for screening corn post-silking root lodging resistance index

Abstract

The present application relates to the field of corn root lodging resistance evaluation, and particularly relates to a method for screening corn post-silk root lodging resistance indexes. Different corn varieties or hybrid combinations with different root lodging resistance characteristics are selected, and at the silking stage, root system configuration traits, root anchorage, and plant inclination recovery degree indexes are investigated. Through principal component analysis, grey correlation degree analysis, and cluster analysis, indexes reflecting root lodging occurrence rate are screened, and according to the index coefficient of variation normalization value and the correlation degree weight value, the indexes are sorted, combined with the root system configuration characteristics of the corn varieties with root lodging resistance, the interval range of the corn root lodging resistance indexes and key indexes is identified, and the root lodging resistance characteristics are classified. The present application clarifies the root system index characteristics of the corn varieties with root lodging resistance and the root lodging resistance evaluation method, and provides a basis for quickly screening corn varieties with root lodging resistance and mining root lodging resistance genes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of hybrid combination identification of corn breeding, and particularly relates to a method for screening corn post-silk resistance to root lodging, which identifies corn resistance to root lodging and its evaluation index through key indexes such as the number of above-ground node roots, the configuration traits of above-ground node roots, root anchoring force, and the recovery degree of plant inclination. BACKGROUND

[0002] With the continuous improvement of agricultural production technology, full mechanization has become one of the main directions of agricultural development in China. The basic condition for realizing mechanized management and harvesting is the strong standing ability of crops, that is, the plants have strong resistance to lodging. Corn is one of the three major food crops in China, and full mechanization of corn production will save a large amount of labor. Breeding corn varieties with strong resistance to lodging is the main goal of mechanized management and harvesting. During the period from corn silking to maturity, due to the influence of natural disasters such as summer rainfall and strong winds, plants are prone to lodging. The ventilation and light transmittance of the leaves of the lodged plants decrease, and the photosynthetic capacity is damaged, which seriously affects the accumulation of dry matter, reduces yield, and deteriorates quality, making harvesting difficult. The average annual yield loss caused by lodging in China is 5-25%. Corn lodging includes stem folding and root lodging, and most of the lodging is ultimately caused by the weak support ability of the root system under the conditions of high soil moisture and strong wind.

[0003] In corn production, there are many factors that affect corn lodging. Among them, the cultivation conditions and meteorological factors during corn growth are the main causes of corn lodging, including seeding depth, seeding density, etc., and meteorological factors include typhoons, continuous rain, etc. The key factor affecting corn lodging is the variety or genotype, therefore, breeding varieties with strong resistance to lodging is the core to overcome corn lodging. At present, many varieties are approved every year in China, and the identification of resistance to lodging mainly relies on the multi-point evaluation during the approval process, that is, through the investigation of the lodging rate caused by disaster weather, but this evaluation is heavily dependent on the meteorological factors during growth, making it difficult to effectively identify the corn resistance to lodging. These varieties approved through the process will completely expose their shortcomings of not being resistant to lodging during the production and promotion process in the event of lodging disaster weather. The lodging caused by meteorological disaster factors is uncertain, with large interannual variation, and lodging does not occur in most years due to the absence of strong wind and heavy rain, therefore, it cannot be completely relied on to evaluate the resistance to root lodging of corn. Other identification methods are artificially induced lodging, which has a large workload and is not suitable for large-scale variety breeding. At present, there is a lack of effective evaluation index for corn resistance to root lodging. Therefore, it is of great significance to study the root configuration characteristics of corn varieties with resistance to root lodging, screen uniform resistance to root lodging index, and establish a rapid and accurate evaluation method for resistance to root lodging, which is a key problem to be solved in the process of corn variety breeding and promotion. SUMMARY

[0004] In view of the problems in the prior art identification techniques, the present application provides a method for evaluating the root lodging resistance of corn varieties, a batch of corn varieties and hybrid combinations with different root lodging resistance under the conditions of continuous rain and wind disasters are selected, in the years without lodging disasters under normal cultivation and management, indexes such as root anchorage, recovery degree after plant tilting, and root system configuration traits in the 0-30 cm deep soil layer above and below the ground are investigated, the root system characteristic changes of hybrid combinations with different root lodging resistance are identified, and an evaluation method for root lodging resistance is established and effective indexes are screened.

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] A method for screening post-silk corn root lodging resistance indexes, comprising the following steps:

[0007] (1) Variety selection: investigate the plant lodging under the conditions of continuous rain and wind disasters, and select a batch of corn varieties or hybrid combinations with significant differences in root lodging resistance according to the root lodging rate;

[0008] (2) Index determination: plant the corn varieties or hybrid combinations selected with significant differences in root lodging resistance according to the optimal density of the varieties or hybrid combinations, and investigate the root anchorage index, the recovery degree after plant tilting index, and the root system configuration trait index in the 0-30 cm deep soil layer above and below the ground at the silk stage of the plants under normal cultivation and management in the years without lodging natural disasters;

[0009] (3) Representative test of the measured root system indexes: perform correlation analysis on the root lodging rate and the measured root anchorage index, the recovery degree after plant tilting index, and the root system configuration trait index in the 0-30 cm deep soil layer above and below the ground, select the indexes with positive correlation for principal component and membership function analysis, obtain the comprehensive evaluation value D of the varieties, the D value is highly negatively correlated with the root lodging rate of the varieties, the absolute value of the correlation coefficient is ≥0.8, which indicates that these root system indexes better reflect the root lodging resistance characteristics. The results obtained by using the D value and the root lodging rate for cluster analysis of the varieties are consistent, and the root lodging resistant varieties can be screened out.

[0010] Further, the root anchorage index in step (2) includes the root pulling force F1 at the silk stage.

[0011] Further, the recovery degree index after plant tilting in step (2) is the maximum pulling force value F2 after irrigation at the silk stage to make the plant tilt at an angle of 45°, the included angle between the stem and the ground after recovery, and the root pulling force F3 at this time.

[0012] Further, the root system configuration trait indexes of the 0-30cm soil layer in the step (2) include the number of ground part into ground node root, the number of ground part into ground node root, the length of aerial root before entering the ground, the length of ground node root into soil to the growth lateral root, the angle between ground node root and vertical downward direction, root dry weight, root plate diameter, root number, root number.

[0013] Further, the determination method of the maximum pulling force value F2 of the plant tilted at an angle of 45° after irrigation at the silking stage in the step (2) is as follows: the corn hybrid combination material is subjected to micro-irrigation at the silking stage, and when the soil water content reaches the field water holding capacity (saturation), the plant is uniformly pulled to an angle of 45° with the ground, and the maximum pulling force value F2 is recorded; after the plant is naturally restored for one day, the angle between the plant and the ground is investigated, and the root pulling force F3 at this time is determined.

[0014] The root system index characteristic importance ranking: through the grey correlation degree analysis of the determination indexes, the correlation degree and the weight of each index are obtained.

[0015] Further, the mean value of the index correlation degree weight value and the normalized value of the coefficient of variation is sorted, and the root configuration indexes directly reflecting the resistance to root lodging are obtained in the following order: the length of ground node root into soil to the growth lateral root, the number of ground part into ground node root, the length of aerial root before entering the ground, the root plate diameter, the number of ground part into ground node root, the root dry weight, the root number, and the root number.

[0016] Further, the indexes indirectly reflecting the resistance to root lodging are obtained in the following order: the standing rate, the maximum pulling force value F2 after irrigation to the field water holding capacity at the silking stage, the root pulling force F3, the root pulling force F1 at the silking stage, and the angle between the stem and the ground after the root lodging recovery.

[0017] Further, the index not selected into the principal component and the membership function analysis and related to the root lodging, i.e., the angle between the ground node root and the vertical downward direction of the plant, is determined according to the change of the index value when the root lodging rate is less than 5%, and the indication range of the resistance to root lodging is 35-45°.

[0018] The beneficial effects of the present application are as follows:

[0019] (1) The technical basis of the present application is to select corn varieties with significant differences in resistance to root lodging after continuous rain disasters, and by comparing the root configuration characteristics of corn varieties with severe root lodging and resistance to root lodging, the root system characteristics of corn varieties with resistance to root lodging are fully revealed. The number of ground node roots of corn with severe root lodging is small, and the node roots are almost creeping; the node roots of corn with resistance to root lodging are developed and form an angle of 35-45° with the ground, and the root pulling force is larger than that of corn with easy root lodging. Corn lodging is mostly root lodging, and according to the root system characteristics of corn varieties with obvious resistance to root lodging, effective, easy-to-distinguish and simple-to-determine root system indexes for resistance to root lodging are screened out, which has important significance for guiding corn lodging-resistant breeding and high-yield cultivation.

[0020] (2) The corn has three stages of seedling stage, earing stage and flowering and grain filling stage, the lodging at the seedling stage and the earing stage can be self-standing, but the lodging at the flowering and grain filling stage has relatively great influence on yield. The flowering and pollen shedding is the beginning of the flowering and grain filling stage, the lodging at the stage covers the female ear with the plant and cannot effectively contact the pollen, so that the fertilization and seed setting are seriously affected, the ear grain number is reduced and the yield is decreased, and the root system structure of the corn is basically shaped at the stage, therefore, the research on the root system structure characteristics of the corn at the silking stage is accurate and significant in period, and the determination of the root system index at the stage has practical significance for guiding the corn root lodging resistance. With the corn kernel filling, the gravity center of the plant moves upward, if the anchoring force of the plant root system is weak, the lodging is more likely to occur, therefore, the root pulling force is more representative for directly indicating the root lodging resistance and is more likely to distinguish whether the variety is resistant to the root lodging.

[0021] (3) The application selects the corn hybrid combinations with different root lodging resistance abilities which are tested in the production environment, determines the root system phenotype structure characteristics and the root pulling force at the silking stage, analyzes the correlation between the indexes and the root lodging rate, identifies the key indexes and the change characteristics of the corn root lodging resistance, and classifies the root lodging resistance characteristics according to the indexes, and the analysis results of the indexes on the variety root lodging resistance are consistent with the actual root lodging resistance of the variety in the test field, which further indicates that the indexes and the evaluation method selected by the application are feasible.

[0022] (4) The application clearly indicates the root system index characteristics and the evaluation method of the corn variety resistant to the root lodging, points out the direction for the corn breeding resistant to the root lodging, and provides the basis for quickly screening the corn variety resistant to the root lodging and mining the related genes. The method of the application is suitable for different corn hybrid combinations or varieties, can accurately and truly evaluate and classify the corn variety root lodging resistance, and has important production practice value and theoretical technical support. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Fig. 4 is the cluster analysis results of the root lodging rates (left) and the comprehensive evaluation D values (right) of 40 varieties.

[0024] Figure 2 Fig. 5 is the cluster analysis results of the root lodging rates (left) and the comprehensive evaluation D values (right) of 30 varieties. DETAILED DESCRIPTION

[0025] The application will be further described below in combination with specific embodiments. It should be understood that the following embodiments are only used for describing the application but not for limiting the scope of the application, and those skilled in the art can make some non-essential improvements and adjustments according to the content of the above application.

[0026] Embodiment 1

[0027] A method for screening the corn root lodging resistance index after silking is as follows:

[0028] The materials selected in this embodiment are 40 corn varieties or hybrid combinations with significantly different root lodging rates tested by 5-6 level continuous rain and wind (Table 1), which are used as reference materials for screening root lodging resistance and effectively evaluating root lodging resistance. The test materials in this embodiment were planted in the experimental base of Henan Agricultural University in Xiping, Zhumadian. Typhoon "Wenbiao" landed and formed heavy to heavy rain in many places in the Huanghuaihai region, causing nearly 1.2 million hectares of crops in Anhui, Henan, Shandong and Jiangsu provinces to be affected. Typhoon "Wenbiao" passed through the test field area on August 17-18, 2018, forming 6-7 level gales (Table 2), which directly led to the occurrence of tilt lodging and even flat laying of corn in a large area, and finally caused a serious reduction in corn yield.

[0029] Table 1 Number and name of 40 corn varieties or hybrid combinations popularized in production

[0030]

[0031] According to the influence of typhoon "Wenbiao" on corn lodging, the root lodging and root lodging rate of the 40 test materials were investigated. It was found that among these hybrid combinations, 5 had a root lodging rate of less than 5%, of which numbers 20, 31 and 37 had a lodging rate of zero, and the other two were 17 and 40, with a lodging rate of 2.9% and 4.1%. The lodging rates of 39 and 4 were 9.9% and 10.0%, respectively. In this study, the above varieties with a root lodging rate of less than 10% can be considered as root lodging resistant varieties. The remaining 33 had a lodging rate of more than 46%, of which 7 had a lodging rate of 100%. It can be seen that most of the varieties (82.5%) had a root lodging rate of more than 10%, indicating that they were not resistant to root lodging, and a small part of the varieties (17.5%) had a root lodging rate of 10% or less, which can be used as good materials for studying the root characteristics of root lodging resistant varieties.

[0032] Table 2 Weather conditions when typhoon "Wenbiao" passed

[0033]

[0034] The severity of corn lodging disaster caused by heavy rain and wind further illustrates the urgency of studying root lodging resistant corn varieties. Therefore, further research on the root lodging resistance characteristics of these corn varieties and hybrid combinations with different root lodging resistance was carried out. In the experimental field of Zhengzhou Henan Agricultural University Science and Education Park, each material was sown at its optimal density, with a plot length of 6 m, 6 rows, and a row spacing of 60 cm. Fertilization, watering and pest control were carried out according to the standard corn production field.

[0035] In 2020, the root phenotype characteristics of these hybrid combinations were observed at the silking stage without lodging disasters. Three plants with consistent growth vigor were selected in the middle row of each plot to determine the root pulling force F1 at the silking stage. Then, three plants were also selected for root sampling observation. The root system of the plant was taken with an iron sheet box (without bottom and cover) with a length, width and height of 30 cm. First, the stems of the plant without aerial root growth were cut off, the iron sheet box was sleeved around the plant, and it was completely hammered into the soil. After being dug out, it was the root system of the plant. After washing the soil with fine water, the number of above-ground root layers, total root layers, above-ground root number and total root number, above-ground root length before entering the soil, the angle between the above-ground root and the vertical downward direction (the angle between the first layer of aerial roots and the vertical plant stem downward direction), the length of the above-ground root into the soil to the growth lateral root, the root plate diameter (the maximum diameter of the root plate) and the 75° oven-dried straight constant weight root dry weight were determined.

[0036] At the same time, another part of the hybrid combinations was subjected to micro-sprinkling irrigation at the silking stage until the soil water content reached the field water holding capacity. At this time, the plant was pulled at a uniform speed to form an angle of 45° with the ground, and the maximum pulling force value F2 was recorded. After the plant was naturally restored for one day, the angle between the plant and the ground was investigated, and then the same method was used to determine the root pulling force F3. Among the 40 selected materials, the coefficients of variation of these traits were larger, including the root pulling force F2, the length of the above-ground root into the soil to the growth lateral root, the number of above-ground root layers and the length of the above-ground root before entering the soil (Table 3).

[0037] Table 3 Difference in root phenotype traits of 40 corn varieties and hybrid combinations

[0038]

[0039]

[0040] Correlation analysis of the above indexes found that the angle between the above-ground root and the vertical downward direction was negatively correlated with other indexes. Further comparative analysis of the index found that when the root lodging rate was less than 5%, the range of the index value was 35-45°. Therefore, according to the change of the index value when the root lodging rate was less than 5%, the indicating range of the resistance to root lodging was determined to be 35-45°. Except for the angle between the above-ground root and the vertical downward direction, the other indexes were positively correlated, indicating that there was information overlap between the other indexes, and it was difficult to accurately and directly evaluate the corn resistance to root lodging by using each single index. Therefore, the present application performs principal component and membership function analysis on the indexes which are positively correlated, and obtains the comprehensive evaluation value D of the variety (Table 4). It is found that the absolute value of the correlation coefficient between the D value and the variety root lodging rate is 0.95, indicating that the determined root system indexes better reflect the resistance to root lodging. The results obtained by using the D value and the root lodging rate for cluster analysis of the varieties are consistent, and the varieties resistant to root lodging can be screened out. Figure 1 ​

[0041] Table 4 comprehensive index value, weight, U(Xj), D value and comprehensive evaluation of each test material

[0042]

[0043] Through the grey correlation degree analysis of the determination index, the correlation degree and the weight of each index are obtained, the mean value of the index correlation degree weight value and the variation coefficient is sorted, and the root configuration index directly reflecting the resistance to root lodging is obtained in turn: the length of the aboveground nodal root into the soil to the growth lateral root, the number of layers of the aboveground nodal root into the soil, the length of the aerial root before entering the soil, the root plate diameter, the number of the aboveground nodal root into the soil, the root dry weight, the number of root strips and the number of root layers; the indexes indirectly reflecting the resistance to root lodging are in turn: the stand stalk rate, the maximum tensile force F2 of the 45° angle after the irrigation of the silking stage to the field water holding capacity, the root pulling force F3, the root pulling force F1 of the silking stage, and the stem and ground angle after the root lodging recovery (Table 5).

[0044] Table 5 mean value of the variation coefficient weight and the grey correlation degree weight

[0045]

[0046] Example 2

[0047] A method for screening the index of corn resistance to root lodging after silking is as follows:

[0048] The 30 corn varieties or hybrid combinations selected in this example were planted in the experimental field of Henan Agricultural University in Xiping County, Zhumadian in 2019, and were sowed according to the appropriate density of each test material on June 8 and June 9. The experimental field experienced two consecutive days of gale and rainy weather on July 27-28, with southwest wind of 4-5 levels, and the rainfall on July 27 and 28 was 12.9 mm and 18.9 mm respectively, causing corn lodging in a large area. At this time, the corn was in the silking and powdering period, and the 30 materials showed obviously different resistance to root lodging (Table 6). It was found that among these varieties or hybrid combinations, there were 3 with zero root lodging rate, numbered 12, 20 and 25, and the above-mentioned 3 varieties with root lodging rate not exceeding 10% in the present invention can be regarded as anti-root lodging varieties. The rest had root lodging rate above 10%, and 10 had root lodging rate of 90% or above. It can be seen that the corn lodging disaster occurred this year was not as serious as when typhoon Wengbi passed, but it also caused the root lodging rate of most varieties (90.0%) to exceed 10%, indicating that these materials were not resistant to root lodging, and a part of the varieties (10.0%) had zero root lodging rate, indicating that the resistance to root lodging of the selected materials existed significant differences, which can be used as good materials for studying the root characteristics of anti-root lodging varieties.

[0049] Table 6 numbers and names of 30 corn varieties or hybrid combinations with different resistance to root lodging

[0050]

[0051] The 30 materials were sown and managed normally in Shizhuangcun, Jian'an District, Xuchang City according to their optimum densities, and in the year 2021 without lodging disasters, when they grew to the silking stage, the method of the present application was used, that is, the sampling and measuring method consistent with that in Example 1, to determine and observe the number of root layers, the number of root strips, the length of aerial roots before entering the soil, the length of the above-ground root nodes into the soil to the growing lateral roots, the angle between the above-ground root nodes and the vertical downward direction, the root dry weight, the root plate diameter, the number of root strips, the number of root layers, the root pulling force at the silking stage (F1), the maximum pulling force value (F2) after irrigation at the silking stage to make the plant at an angle of 45°, the angle between the stem and the ground after recovery, and the root pulling force at this time (F3). Among the 30 selected materials, the coefficients of variation of these traits were greater, including the root pulling force F2, the length of the above-ground root nodes into the soil to the growing lateral roots, the number of root layers, and the angle between the above-ground root nodes and the vertical downward direction (Table 7).

[0052] Table 7 Differences in root phenotypic traits of 30 corn varieties and hybrid combinations

[0053]

[0054]

[0055] Correlation analysis of lodging rate and the above-mentioned indicators found that the angle between the above-ground root nodes and the vertical downward direction was negatively correlated with other indicators. Further comparative analysis of this indicator found that when the root lodging rate was less than 5%, the range of the value of this indicator was 35-45°, and it was clear that the indicating range for resistance to root lodging was 35-45°. Principal component and membership function analysis were further performed on the other indicators that were positively correlated, and the comprehensive evaluation value D of the varieties was obtained. Analysis found that the absolute value of the correlation coefficient between the D value and the root lodging rate of the varieties was 0.80, indicating that the determination of these root system indicators better reflected the resistance to root lodging. The results obtained by clustering analysis of the varieties using the D value and the root lodging rate were consistent, and both could screen for root lodging-resistant varieties. Figure 2

[0056] Through gray correlation degree analysis of the determination indicators, the correlation degree and weight of each indicator were obtained. The mean value of the indicator correlation degree weight value and the normalized value of the coefficient of variation was sorted to obtain the root architecture indicators directly reflecting the resistance to root lodging in the following order: the length of the above-ground root nodes into the soil to the growing lateral roots, the number of root layers, the length of aerial roots before entering the soil, the root plate diameter, the number of root strips, the root dry weight, the number of root strips, and the number of root layers; and the indicators indirectly reflecting the resistance to root lodging in the following order: the stem standing rate, the maximum pulling force value F2 after irrigation to the field water holding capacity at the silking stage, the root pulling force F3, the root pulling force F1 at the silking stage, and the angle between the stem and the ground after recovery (Table 8).

[0057] Table 8 Mean values of the coefficient of variation weight and the gray correlation degree weight​

[0058]

[0059] The foregoing is considered as illustrative only of the principles of the application and the forms thereof which are demonstrated by the described embodiments. Further, those skilled in the art will readily recognize that certain of the above described embodiments can include, inter alia, alternate configurations and steps thereof known in the art. Therefore, there is no intention that this application be limited as described unless by the recitations of the claims that follow, or by appropriate wording in the description.

Claims

1. A method for screening indicators of resistance to root lodging after corn silking, characterized in that: Includes the following steps: (1) Investigate the lodging of plants under the conditions of storm and continuous rain disaster, and select a batch of maize varieties or hybrid combinations with significant differences in resistance to root lodging based on the root lodging rate; (2) Selected maize varieties or hybrid combinations with significant differences in resistance to lodging are planted at the optimal density of the variety or hybrid combination and under normal cultivation and management. In years without lodging natural disasters, the root anchoring force index, the recovery degree index after the plant tilts, and the root system configuration index at the silking stage are investigated. (3) Correlation analysis was performed on the root lodging rate, the measured root anchoring force index, the recovery degree index after plant tilting, and the root system configuration traits indexes at soil depths of 0-30cm above ground and below ground. Principal component and membership function analysis were performed on the positively correlated indicators to obtain the comprehensive evaluation value D of the variety. The D value was highly negatively correlated with the root lodging rate of the variety, and the absolute value of the correlation coefficient was ≥0.8, indicating that these root system indicators reflected the root lodging resistance characteristics well. By analyzing the grey relational degree of the measured indicators, the correlation degree and weight of each indicator are obtained. The root architecture indices that directly reflect resistance to root lodging are sorted by the mean values ​​of the correlation weights and the normalized values ​​of the coefficients of variation. The indices are as follows: length of aboveground nodes from root entry into soil to lateral root growth, number of aboveground nodes in the ground, length of aerial roots before entry into soil, root plate diameter, number of aboveground nodes in the ground, root dry weight, number of roots, and number of root layers. The index correlation weight values ​​and the mean values ​​of the normalized coefficient of variation were sorted to obtain the indirect indicators reflecting resistance to root lodging as follows: stalk standing rate, maximum tensile force F2 at a 45° angle after irrigation to field water holding capacity during the silking stage, root pull-out force F3, root pull-out force F1 during the silking stage, and the angle between the stem and the ground after root lodging recovery. For the indicators that were not selected for principal component and membership function analysis and were related to root lodging, namely the angle between the above-ground root node and the vertical downward direction of the plant, the range of their indication for resistance to root lodging was determined to be 35-45° based on the change in the indicator value when the root lodging rate was less than 5%. The results obtained by cluster analysis of varieties using D value and root lodging rate were consistent, and both could screen out root lodging resistant varieties. In step (2), the root anchoring force index includes the root pull-out force F1 during the silk-spinning period; In step (2), the recovery index of the plant after tilting is the maximum pulling force F2 that makes the plant tilt at a 45° angle after watering during the silking period, the angle between the stem and the ground after recovery, and the root pulling force F3 at this time. In step (2), the root system configuration characteristics of the above-ground and underground soil layers (0-30cm) include the number of above-ground root layers, the number of above-ground root segments, the length of aerial roots before they enter the ground, the length of above-ground root segments from the soil to the growth of lateral roots, the angle between above-ground root segments and the vertically downward direction, root dry weight, root plate diameter, number of root segments, and number of root layers.

2. The method for screening indicators of resistance to root lodging after corn silking according to claim 1, characterized in that: The method for determining the maximum pulling force F2 of the plant tilting at a 45° angle after irrigation during the silking stage in step (2) is as follows: the experimental field maize hybrid combination material is treated with micro-sprinkler irrigation during the silking stage. When the soil moisture content reaches the field water holding capacity saturation, the plant is pulled at a uniform speed to a 45° angle with the ground and the maximum pulling force F2 is recorded. After the plant has recovered naturally for one day, the angle between the plant and the ground is investigated, and the root pull-out force F3 is measured at this time.

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