Method for evaluating corn stem breaking resistance

Abstract

The invention discloses a method for evaluating the stem breaking resistance of corn. According to the method, the thickness of the thick-walled cells of the stem cortex is measured, and the larger the thickness is, the higher the corn stem breaking resistance is. According to the method, the stem folding condition of a series of corn inbred line materials after rainstorm is evaluated; it is found that the root fracture resistance of the corn material is related to the thickness of the thick-walled cells of the stalk cortex, and the thickness of the thick-walled cells of the stalk cortex of the corn can be used for evaluating the stem fracture resistance of the corn.

Description

Technical Field

[0001] This invention belongs to the field of maize field phenotypic identification technology, specifically relating to a method for assessing maize's resistance to stem breakage. Background Technology

[0002] Corn is my country's largest grain crop, accounting for 23% of global production annually, and is crucial for ensuring food security, promoting economic development, and alleviating the energy crisis. However, with climate change, the frequency of extreme weather events is increasing in China's major corn-producing areas, leading to a rise in lodging. Lodging is a major factor limiting global grain yields. It affects dry matter assimilation and harvesting, resulting in yield reductions of up to 80%. Lodging can be defined as the grain stalk deviating from its vertical position and can be divided into stem lodging and root lodging. Stem lodging refers to the stalk bending to the ground or breaking, while root lodging refers to the root system failing to provide support. Mechanical harvesting of lodged crops is difficult and usually leads to yield loss. In 2020, Typhoon Maysak caused widespread corn stalk lodging in Northeast China. In high-density cornfields, stem lodging accounts for more than 60% of all lodging, resulting in annual corn yield losses of up to 1 million tons in China. Therefore, developing lodging-resistant varieties has become a major goal of modern corn breeding, and achieving this goal depends on the identification of lodging-resistant corn inbred lines. Therefore, it is imperative to conduct a large-scale assessment of the lodging resistance of maize germplasm resources.

[0003] Lodging is influenced by environmental factors and plant characteristics. Environmental factors include wind, rain, diseases, and pests. Among plant characteristics, plant height has a significant impact on crop lodging resistance. Since the 1960s, the introduction of semi-dwarf varieties has significantly increased the yields of rice and wheat by enhancing lodging resistance. However, if maize plants are too short, ventilation and light will be insufficient, leading to a decrease in yield. Studies have shown that the lodging resistance of maize stalks depends on the diameter and length of the internodes at the base of the stalk, the cross-sectional area of ​​the stalk, and the ear height. The cell wall thickness of the maize stalk, the total vascular bundle area, the area of ​​the outer vascular bundle, and the diameter of the auxiliary axis in the stalk cross-section also affect the lodging resistance of maize stalks. However, most studies on how morphological and anatomical characteristics affect maize stalk lodging have been conducted under laboratory conditions. The effects of morphological and anatomical characteristics on maize stalk lodging under field conditions have not been extensively studied. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the resistance of maize to stem breakage.

[0005] A method for assessing maize's resistance to stem breakage involves measuring the thickness of thick-walled cells in the stalk cortex; the greater the thickness, the stronger the maize's resistance to stem breakage.

[0006] The stem cortex thick-walled cells have a thickness of over 36 μm, making it a corn variety resistant to stem breakage.

[0007] The beneficial effects of this invention are as follows: This invention evaluated the stem breakage of a series of maize inbred lines after a storm; it was found that the root breakage resistance of maize materials is related to the thickness of the sclerenchyma cells in the stem cortex, and the thickness of the sclerenchyma cells in the maize stem cortex can be used to evaluate the stem breakage resistance of maize. Attached Figure Description

[0008] Figure 1 Screening for stem breakage resistant and stem breakage sensitive materials under natural conditions.

[0009] Figure 2 Plant height (A), stem diameter at the third internode (B), and stem piercing force (C) are shown for stem breakage resistant material (LR) and stem breakage sensitive material (LS); in the figure, LR: stem breakage resistant material, LS: stem breakage sensitive material.

[0010] Figure 3 Anatomical structural analysis of stem-break resistant and stem-break sensitive materials; (A) Representative images of the third intersegmental microstructure of the extreme materials; scale bars represent the thickness of cortical and vascular bundle thick-walled cells, respectively; the scale bar for cortical thick-walled cell images is 30 μm, the scale bar for vascular bundle thick-walled cell images is 50 μm, and the scale bar for vascular bundle number images is 250 μm; (B) Cortical thick-walled cell thickness of the extreme materials; (C) Cortical vascular bundle area of ​​the extreme materials.

[0011] Figure 4 The thickness of the cortical thick-walled cells is used for materials resistant to stem breakage and materials sensitive to stem breakage.

[0012] Figure 5 To observe the cross-sections of stem-break resistant and stem-break sensitive materials using scanning electron microscopy; scale bar is 100 μm, CS: cortical sclerenchyma cells, VS: vascular bundle sclerenchyma cells, VC: stele, MX: secondary xylem, PX: primary xylem, P: phloem. Detailed Implementation

[0013] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention. Example 1

[0014] Forty-three maize inbred lines were planted on May 13, 2020, at the Shunyi Agricultural Experiment Station of the Institute of Crop Science, Chinese Academy of Agricultural Sciences (40.13°N, 116.65°E). The soil type of the experimental field was typical alkaline (pH 8.2) brown soil. Soil composition analysis showed that per kilogram of dry soil, there were 18.8 g of organic matter, 85.79 mg of available nitrogen (N), 40.7 mg of available phosphorus (P), and 151.2 mg of available potassium (K). Before sowing, 750 kg of compound fertilizer (15 N-15 P2O5-15 K2O) was applied per hectare as basal fertilizer. At the tasseling stage of maize, 450 kg of urea (N≥46.4%) was applied per hectare as top dressing. The experiment used an α(0,1) Latin square design, randomly arranged, with each material sown in two rows, 3 m long, 60 cm row spacing, and 25 cm plant spacing, with two replicates. Irrigation was carried out on May 20 and June 20, 2020, with each irrigation being 70mm.

[0015] The experimental field was hit by a storm in July 2020, with a total hourly rainfall of approximately 50 mm and a maximum wind speed exceeding 20 m / s. Figure 1 A) Extreme weather provides an excellent opportunity to evaluate the lodging resistance of maize germplasm under natural conditions. Therefore, the field lodging resistance of 443 maize inbred lines under natural conditions was assessed. It was found that the stems of inbred lines LI55, LI68, CX41, CX77, and DR-F did not bend or break during heavy rain, and these five inbred lines were considered stalk-resistant materials. In contrast, the stems of Q1261, Chuan273, 14HF1994, JI495, and CML338 broke during heavy rain, with breakage rates ranging from 20.0% to 42.9%. Figure 1 B) believes that these five inbred lines are materials sensitive to stem breakage. Example 2: Morphological characteristics of stem-break-resistant materials and stem-break-sensitive materials The plant height and stem morphology characteristics of the five stem-bending resistant materials and the five stem-bending sensitive materials were observed. The results showed no significant differences in plant height, stem diameter at the third internode above ground, and stem piercing force between the stem-bending resistant materials and the stem-bending sensitive materials. Figure 2 These results indicate that morphological traits are not the key factors determining the lodging resistance of these maize lines.

[0016] Example 3 Anatomical characteristics of stem-stretch-resistant and stem-stretch-sensitive materials Further investigation was conducted on the anatomical structure of the third internode of the stem in both stem-bending resistant and stem-bending sensitive materials. The results revealed significant differences in the microstructure of the vascular bundles near the cortex and epidermis. Compared to the stem-bending sensitive material, the stem-bending resistant material exhibited a significantly increased thickness of cortical sclerenchyma cells and a larger vascular bundle area. The average thickness of the cortical sclerenchyma cells in the stem-bending resistant material was 45.5 μm, which was twice that of the stem-bending sensitive material. Figure 3 Among stem-break resistant materials, DR-F has the thinnest cortical sclerenchyma cells (35.8 μm), but it is still about 14% thicker than Chuan273, the material with the thickest cortical sclerenchyma cells among stem-break sensitive materials. Figure 4 This result indicates that the thickness of the cortical sclerenchyma cells contributes to improving the stem breakage resistance of maize. To verify these results, we randomly selected two stem breakage-resistant varieties (LI68 and CX77) and two stem breakage-sensitive varieties (Q1261 and 14HF1994), and observed their third stem nodes using scanning electron microscopy. We found that the arrangement of cortical sclerenchyma cells in the stem breakage-resistant material was denser than that in the stem breakage-sensitive material, and the thickness of the vascular bundle sclerenchyma cells near the epidermis in the stem breakage-resistant material was also greater than that in the stem breakage-sensitive material. Figure 5 ).

[0017] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for evaluating the resistance of maize to stalk breakage, characterized in that, The thickness of the thick-walled cells in the stem cortex is measured; the greater the thickness, the stronger the corn's resistance to stem breakage.

2. The method for evaluating the resistance of maize to stalk breakage according to claim 1, characterized in that, The stem cortex thick-walled cells have a thickness of over 36 μm, making it a corn variety resistant to stem breakage.

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