A method for evaluating the early root growth ability of melon seedlings

Abstract

The present invention belongs to the field of melons, and specifically relates to a method for evaluating the early root development ability of melons in the seedling stage. The method for evaluating the early root development ability of melons in the seedling stage described in the present invention uses black soil as a medium to batch cultivate plant seedlings, which is convenient for image analysis and data collection. The measured main root length, total lateral root length, and lateral root number variation range are evenly distributed and continuous, and the variation difference is significant, which can reflect the difference in root growth conditions of different plant materials. The evaluation method described in the present invention can be used to evaluate the early development ability of different melon materials, which not only saves experimental time, but also has high experimental repeatability and stability, and good data reproducibility, repeatability, and stability. It can complete the evaluation of the early root development ability of multiple melon materials at one time, and realize the high-throughput evaluation of the early root development ability of melons.

Description

Technical Field

[0001] The invention belongs to the field of melons, and particularly relates to a method for evaluating the early root growth ability of melons at the seedling stage. Background Art

[0002] The ability of plants to germinate early in the seedling stage is mainly based on several key indicators, including growth rate, root development, leaf number and area, and photosynthetic efficiency. These indicators jointly determine the growth status of the plant in the seedling stage, which in turn affects its subsequent growth potential and yield. Among them, the growth and development of the root system directly affects the plant's ability to absorb water and nutrients, and is one of the important evaluation indicators for the ability of plants to germinate early in the seedling stage. Indicators that usually reflect the growth status of the root system include taproot length, lateral root length, number of lateral roots, root surface area, etc. Varieties with strong early germination ability have obvious advantages in root growth and development, and can lay the foundation for the later growth of the plant.

[0003] Muskmelon is native to the tropics and is a widely cultivated fruit, ranking among the top ten fruits in the world. Compared with other Cucurbitaceae crops such as pumpkin and gourd, melon has a weaker root system, poor regeneration ability, low nutrient utilization rate, and poor early root development ability. Therefore, screening out melon varieties with well-developed root systems and high early root development ability is a crucial link in melon variety selection and breeding, and has become an important research direction. However, the current methods for evaluating the early root development ability of melons have poor stability, which is not conducive to the research on melon root-related genetics and breeding, and seriously restricts the variety selection and variety improvement of melons. Therefore, this study intends to develop an efficient and stable method for evaluating the early root development ability of melons, so as to promote research on melon root development, nutrient utilization, and the selection and breeding of excellent varieties. Summary of the invention

[0004] The invention provides a method for evaluating the early root growth ability of melon seedlings, which can quickly evaluate the early root growth ability of plants in the seedling stage and greatly improves the stability.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A method for evaluating the early root growth ability of melon seedlings comprises the following steps:

[0007] (1) Germination

[0008] Select melon seeds that are uniform in size and plump, and germinate them until the seeds turn white;

[0009] (2) Loading soil

[0010] Adjust the soil moisture content to 40%, add moisture to the soil evenly by spraying, and turn the soil constantly to ensure even distribution of moisture; select cultivation boxes of the same size, punch holes in the bottom and fill them with the same amount of soil, with a filling height of 25-30cm;

[0011] (3) Sowing

[0012] Sow the seeds in the cultivation box and cover the surface of the seeds with soil after sowing;

[0013] (4) Cultivation

[0014] Place the cultivation box in an incubator at an angle, with the side of the seeds facing white downward so that the roots can grow flat against the side wall of the cultivation box, and the side wall against which the roots are attached is made of transparent material; no watering is required during the cultivation process;

[0015] (5) Photo taking and data processing

[0016] On the fifth day after sowing, take photos to obtain root system images, obtain data on the taproot length, total lateral root length, number of lateral roots and / or comprehensive score of the root system, and evaluate the early root growth ability of the melon seedlings based on the obtained data;

[0017] The calculation method of the comprehensive score is: standardize the three indicators of main root length, total lateral root length and lateral root number, and the calculation method of the standardized value S of each indicator is: S= (XX min ) / (X max -X min ), where X is the measured value of the index of the sample to be tested, X min is the minimum value of the indicator, X max The maximum value of this indicator; the comprehensive score S 总 =S1+S2+S3, where S1, S2, and S3 are the standardized values ​​of the three indicators: main root length, total lateral root length, and lateral root number, respectively.

[0018] Furthermore, the length, height and width of the cultivation box are 185×306×21 mm, and there is a gap with a width of not less than 15 mm inside the box to accommodate the growth of the seed roots; the white end of the seed faces the side formed by the length and height of the cultivation box; during the sowing process, the white end of the seed is kept at the same distance from the side wall of the cultivation box.

[0019] Furthermore, in the step (2), the soil moisture content is measured by weighing a certain weight of soil and placing it in an oven to dry it to a constant weight, and the soil moisture content = (soil weight before drying - soil weight after drying) / soil weight after drying; in the step (2), a hole with a diameter of 0.5 cm is uniformly punched in the middle of the bottom of the cultivation box.

[0020] Furthermore, in step (2), the soil is black soil, the weight of the black soil in each cultivation box is 900-1000 g, and the soil filling height is 28.5 cm.

[0021] Furthermore, in the step (3), the surface of the seeds is covered with 1 cm of soil after sowing.

[0022] Furthermore, in the step (4), the cultivation box is placed in a turnover box at an angle of 30° to the horizontal direction, and then the turnover box is placed in the incubator.

[0023] Furthermore, in step (4), the temperature in the incubator is set at 35°C, the humidity is 40-50%, the light cycle is 3.5 hours of light, 0.5 hours of dark treatment, and 6 cycles per day.

[0024] Furthermore, in the step (5), the longer the taproot is, the stronger the early germination ability of the melon is; the longer the total length of the lateral roots is, the stronger the early germination ability of the melon is; the more the number of lateral roots is, the stronger the early germination ability of the melon is; and the higher the comprehensive score is, the stronger the early germination ability of the plant is.

[0025] Application of the evaluation method described above to distinguish the early emergence ability of melon.

[0026] Further, in the application, the taproot length, total lateral root length, number of lateral roots and / or comprehensive score of the melon are measured by the above-mentioned evaluation method; the longer the taproot length is, the stronger the early germination ability of the melon is; the longer the total lateral root length is, the stronger the early germination ability of the melon is; the more the lateral roots are, the stronger the early germination ability of the melon is; the higher the comprehensive score is, the stronger the early germination ability of the melon is.

[0027] Beneficial effects of the present invention:

[0028] The method for evaluating the early root development ability of melon seedlings described in the present invention uses black soil as a medium to cultivate melons in batches. The medium and the white root system have a sharp contrast, which is convenient for image analysis and data collection. The main root length, the total length of the lateral roots, and the number of lateral roots measured five days after sowing have a uniform and continuous distribution of variation ranges, and the variation difference is significant, which can reflect the difference in the root growth conditions of different melon materials, and then evaluate the early development ability of different melon materials. The identification cycle is shortened without affecting the root characteristics, which not only saves experimental time, but also has high experimental repeatability and stability. The evaluation method described in the present invention is used for the evaluation of the early root development ability of melon seedlings. The measured data has good reproducibility, repeatability, and stability. It can complete the evaluation of the early root development ability of multiple melon materials at one time, realize the high-throughput evaluation of the early root development ability of melons, and greatly improve the evaluation efficiency of the early root development ability of melons. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 This is the color comparison of black soil, nutrient soil and black cloth, where A is black soil, B is nutrient soil, and C is black cloth.

[0031] Figure 2 Figure 2 shows the root phenotypes under three culture media. Figure A is the polyethylene bag hydroponic method, Figure B is the nutrient soil culture method, and Figure C is the black soil culture method. Figure D shows the root identification in the black soil medium Photoshop software. Figure E shows the melon seedlings cultivated in the black soil medium culture box.

[0032] Figure 3 The variation in taproot length of 20 melon materials taken at four different times.

[0033] Figure 4 This is the correlation between the taproot lengths of 20 melon materials between two replicates when the first photo was taken.

[0034] Figure 5 This is the correlation between the taproot lengths of 20 melon materials between two replicates when taking the second photo.

[0035] Figure 6 This is the correlation between the taproot lengths of 20 melon materials between two replicates when taking the third photo.

[0036] Figure 7 The correlation between the taproot lengths of 20 melon materials between two replicates at the fourth photo shoot.

[0037] Figure 8 These are the root phenotypes at three moisture contents under the black soil culture methods. A is method one, water saturation state, B is method two, soil moisture content of 30%, and C is method three, soil moisture content of 40%.

[0038] Fig. 9 The variation of main root length, total lateral root length and number of lateral roots of 20 melon materials with different water contents.

[0039] Fig.10 The effect of different water contents on the length of the taproot.

[0040] Fig.11 The effect of different water contents on lateral root length.

[0041] Fig.12The effect of different water contents on the number of lateral roots.

[0042] Fig.13 The figure shows the influence of different culture conditions on the root phenotype stability, wherein Rep1 is the culture condition of the present invention, and Rep2 is the normal culture condition.

[0043] Fig.14 Correlation between main root length, total lateral root length and lateral root number of 100 melon materials between two replicates. Rep1 and Rep2 are two replicate experiments.

[0044] Fig.15 The phenotypic variation of taproot length, total lateral root length and lateral root number of 100 melon materials. The horizontal axis represents two independent experimental repetitions.

[0045] Fig.16 A bar graph ranking the taproot lengths of 100 melon accessions.

[0046] Fig.17 Bar graph ranking the total length of lateral roots of 100 melon accessions.

[0047] Fig.18 A bar chart ranking the number of lateral roots of 100 melon accessions.

[0048] Fig.19 is the comprehensive score S of 100 melon materials 总 Sorted column chart. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example 1

[0051] A method for evaluating the early root growth ability of melon seedlings comprises the following steps:

[0052] (1) Germination

[0053] After removing impurities, select melon plant seeds of uniform size and fullness. Different materials are numbered and then germinated until the seeds turn white. The germination method is: put the selected seeds into a mesh bag, soak them in 55℃ warm water for 3-4 hours, take them out and wrap them with wet cloth, cover them with plastic wrap to keep them moist, and germinate them at 28℃ for 18-24 hours.

[0054] (2) Loading soil

[0055] Select a transparent box of the same size as the cultivation box, and make a hole with a diameter of 0.5 cm at the bottom. After making the hole, fill it with the same amount of soil, and the height of the soil filling is 25-30 cm; measure the soil moisture content one day in advance before filling the soil, and adjust it according to the measured soil moisture content to make the soil moisture content reach 40%. You can evenly add moisture to the soil by spraying, and keep turning the soil to ensure uniform distribution of moisture; in this embodiment, in the above embodiment, a flat transparent acrylic box is selected as the cultivation box. The length, height and width of the acrylic box are 185×306×21 mm, the thickness of the acrylic board is 3 mm, and there is a gap of 15 mm in width inside the box for filling soil and sowing seeds. The box weighs 370g. The soil selected is Northeast black soil, and the weight of black soil in each cultivation box is 900-1000g. For ease of operation, the total weight of the acrylic box and soil is 1300 g.

[0056] Method for measuring soil moisture content: Weigh a certain weight of soil and put it in an oven to dry to constant weight. Soil moisture content = (soil weight before drying - soil weight after drying) / soil weight after drying.

[0057] (3) Sowing

[0058] Number the side of the box with a larger area (the side composed of the length and height), and the white end of the seed faces the numbered side. After sowing, cover the surface of the seed with 1 cm of soil; sow 2 seeds in each box. During the sowing process, make sure that the white end of the seed is at the same distance from the side wall of the cultivation box, and the white end of the seed faces the same direction, ensuring that the white end of the seed is at the same distance from the side wall of the cultivation box.

[0059] (4) Cultivation

[0060] Place the cultivation box in a turnover box at an angle of 30° to the horizontal plane, and place it with the numbered side facing down, so that the roots can grow flat against the side wall of the cultivation box. Keep the number of acrylic boxes in each turnover box the same, and place the turnover box in an incubator for cultivation. During the cultivation process, keep the soil moisture content at 40%. Set the temperature in the incubator to 35°C, the humidity to 40-50%, and the photoperiod to 3.5 hours of light and 0.5 hours of dark treatment, with 6 cycles per day.

[0061] (5) Photo taking and data processing

[0062] On the fifth day after sowing, photos were taken to obtain root system pictures, and the root system pictures were processed with ImageJ software to measure the root system data. The measured root system data included: main root length, total lateral root length, and number of lateral roots. A comprehensive score was calculated based on the measurement results. The longer the main root length, the stronger the early germination ability of the melon; the longer the total lateral root length, the stronger the early germination ability of the melon; the more lateral roots there are, the stronger the early germination ability of the melon; the higher the comprehensive score, the stronger the early germination ability of the plant.

[0063] Since the white side of the seeds is placed downward, the roots of the seeds will grow toward the side wall of the cultivation box with the number after sowing. After touching the side wall of the cultivation box, they will continue to grow along the inclined direction of the side wall of the cultivation box, which makes it convenient to take photos of the roots directly. The size of the turnover box is 610×420×200 mm.

[0064] In this embodiment, the comprehensive score is calculated by standardizing the three indicators of main root length, total lateral root length and number of lateral roots, and the standardized value S of each indicator is calculated as follows:

[0065] S=(XX min ) / (X max -X min ), where X is the measured value of the index of the sample to be tested, X min is the minimum value of the indicator, X max is the maximum value measured for this indicator;

[0066] Comprehensive score 总 =S1+S2+S3, where S1, S2, and S3 are the standardized values ​​of the three indicators: main root length, total lateral root length, and lateral root number, respectively.

[0067] 1. Screening of culture conditions

[0068] 1. Effects of different culture methods on root phenotypes

[0069] In order to determine the culture method of melon seedlings with quantifiable root system, three methods were adopted: polyethylene bag hydroponic method, nutrient soil culture method and black soil culture method.

[0070] A total of 20 melon germplasm resources were provided by the Zhengzhou Fruit Research Institute of the Chinese Academy of Agricultural Sciences, including thick-skinned and thin-skinned types. Pin's peat 0-10 mm nutrient soil, Northeast black soil, 185×306×21 mm (length / height / width) transparent acrylic box (internal gap 15 mm, acrylic board thickness 3 mm, weight 370g), 610×420×200 mm turnover box.

[0071] Specific steps of the three methods

[0072] (1) Polyethylene bag hydroponics method

[0073] The experimental steps of this method include germination, polyethylene bag hydroponics, photo observation and data processing. The specific operations are as follows:

[0074] Germination: After removing impurities, select 15 seeds of uniform size and fullness from 20 melon materials, mark the number of the melon material on the label, and put them into a mesh bag. Soak the melon seeds in 55 ℃ warm water for 3-4 hours, take them out and wrap them with wet cloth, cover them with plastic wrap to keep them moist, and germinate them at 28 ℃ for 18-24 hours.

[0075] Polyethylene bag hydroponics: Place the whitened seeds vertically in the middle of a polyethylene bag filled with glass fiber filter paper, sow 10 melon seeds evenly in each bag, and add 35 ml of pure water. Place the polyethylene bag in a specific acrylic rack, and then place the acrylic rack in an incubator. Set the temperature in the incubator to 35°C, the humidity to 40-50%, the photoperiod to 3.5 hours of light, 0.5 hours of dark treatment, and 6 cycles per day. When the taproot grows to 3-5 cm, remove the seedlings with inconsistent root growth, and keep three seedlings with consistent root growth for further cultivation.

[0076] Photo observation: Take photos starting 72 hours after sowing, and then take photos every 24 hours, for a total of four times, to obtain root system images and observe root growth.

[0077] Data processing: Observe the root system every day after sowing. Since the root system at the third photo shoot has the greatest difference between varieties and the best repeatability, ImageJ software is used to process the root system data of that day. Set the image scale, measure the root length, record the main root length, total lateral root length, and the number of lateral roots, and summarize the data in an Excel table for analysis.

[0078] (2) Nutrient soil culture method

[0079] The experimental steps of the method include germination, soil filling, sowing, water injection, cultivation, photographing and observation, and data processing. The specific operations of germination, photographing and observation, and data processing are the same as above, and the other experimental operations are as follows;

[0080] Filling the soil: Use a hole puncher to punch a hole with a diameter of 0.5 cm in the middle of the bottom of the box, and fill the acrylic box with nutrient soil. The total weight of the acrylic box and soil is 1300 g, and the height of the soil is 28.5 cm. Sowing: Use a marker to write the material number on the top of the acrylic box, and sow two seeds in each acrylic box at an equal distance. When sowing, make sure that the white end of the seed faces the numbered direction. After sowing, cover the surface of the seed with 1 cm of soil.

[0081] Water injection: Add 500 ml of pure water to each acrylic box to fully saturate the soil with water.

[0082] Cultivation: Place the acrylic box tilted in the turnover box with the numbered side facing down. Keep the number of acrylic boxes in each turnover box consistent. Place the turnover box in the incubator. Set the temperature in the incubator to 35°C, the humidity to 40-50%, the photoperiod to 3.5 h light, 0.5 h dark, and 6 cycles per day.

[0083] (3) Black soil cultivation method

[0084] The experimental steps of this method include germination, soil filling, sowing, watering, cultivation, photographing and observation, and data processing. Except for soil filling, other specific operations are the same as above. The soil filling operation is as follows:

[0085] Filling the soil: Use a hole puncher to make a uniform hole with a diameter of 0.5 cm in the middle of the bottom of the box, and fill the acrylic box with black soil. The total weight of the acrylic box and the soil is 1300 g, and the height of the soil is 28.5 cm.

[0086] 1.2 Experimental Results

[0087] Figure 1 For black soil ( Figure 1 A in), nutrient soil ( Figure 1 B) and black cloth color ( Figure 1 The RGB color value of black cloth is (4, 4, 5), the RGB color value of black soil is (15, 15, 21), and the RGB color value of nutrient soil is (60, 55, 53).

[0088] 1.3 Root phenotypes under different culture media

[0089] Figure 2 The root phenotypes under three culture media are shown. Figure 2 A in the figure shows that the root growth is unstable, with large differences between varieties and poor repeatability between individuals. On the one hand, it is because the glass fiber filter paper and the polyethylene bag are easy to fit together, resulting in uneven moisture conditions and oxygen distribution, leading to unstable root growth; on the other hand, during the culture process, water mist or water column will form in the germination bag, making it impossible to obtain high-quality root images, and the quantification of root characteristics is poor, which is not conducive to the later analysis of root phenotypes. Figure 2 The root system images obtained by the black soil culture method (B) contain a lot of white impurities, which affects the judgment of the root system and makes it impossible to quantify the root system characteristics, which is not conducive to the later processing of the images. Therefore, the above two methods are not feasible. Figure 2 (C) The roots grow well and the background is uniformly black, which contrasts sharply with the white roots. This is conducive to the quantification of root characteristics during image processing. Therefore, it was finally determined that black soil was used as the medium for the identification of root phenotypes. Figure 2Figure D shows the identification of the ground root system in black soil medium Photoshop software. Figure 2 Figure E shows melon seedlings grown in an incubator.

[0090] 2. Effects of different shooting times on root growth

[0091] In order to determine the root growth time that can reflect the differences between different materials, a melon cultivation experiment was carried out according to the method of Example 1. The sowing time was taken as the 0th day, and the roots were photographed 4 times at different times. The taproot lengths of different materials at the first (3rd day after sowing), second (4th day after sowing), third (5th day after sowing) and fourth (6th day after sowing) photography were compared and analyzed.

[0092] Figure 3 The figure shows the variation of taproot length of 20 melon materials at four shooting times. As can be seen from the figure, the main variation range of taproot length was 10-13cm, 14-17cm, 16-21cm, and 21-26cm when shooting the first, second, third, and fourth times, respectively. Larger phenotypic variation is the basis of genetic analysis, and the third and fourth times are better than the first and second times.

[0093] Figure 4-7 The figure reflects the correlation between the taproot lengths of the 20 melon materials when they were photographed for the first, second, third and fourth times. The r value represents the correlation coefficient between the repetitions. As can be seen from the figure, the correlation coefficients r between the taproot lengths measured in the four photographs and the two repetitions are 0.8554 ( Figure 4 )、0.8919( Figure 5 )、0.9300( Figure 6 ), 0.9275 ( Figure 7 ). Therefore, from the perspective of the reproducibility of taproot length, the third and fourth shots are better than the first and second shots. The phenotypic conditions and correlations of the third and fourth shots are similar. The third shot is earlier than the fourth, which can shorten the root identification cycle. Therefore, we used the root system pictures taken for the third time (5 days) for data processing and analysis.

[0094] 3. Effect of soil moisture on root system

[0095] Since the amount of water content has a significant effect on root growth, and the stability of root growth under different water conditions is also different, a melon cultivation experiment was carried out according to the method of Example 1, and three water gradients were set in the black soil culture method, with water contents of 30%, 40% and 50%, respectively, to identify the root growth ability of 20 identical melon materials.

[0096] 3.1 The specific steps are as follows

[0097] The experimental steps of the method include germination, measuring soil moisture content, soil mixing, soil filling, sowing, cultivation, photographing and observation, and data processing. The specific operations of germination, measuring soil moisture content, sowing, cultivation, photographing and observation, and data processing are the same as above. Other experimental operations are as follows:

[0098] a. Soil mixing: Measure the soil moisture content one day in advance, calculate and adjust the soil moisture content to 30%, 40% and 50% respectively. You can add moisture to the soil evenly by spraying and constantly turn the soil to ensure even distribution of moisture.

[0099] b. Filling with soil: Put the mixed soil into the acrylic box to a height of 28.5 cm.

[0100] 3.2 Root phenotypes at three water contents under black soil culture methods

[0101] Figure 8 The root phenotypes of three water contents under the black soil culture method. Under 50% water content ( Figure 8 Figure A in the figure shows that the root system of the same material is consistent, but the soil is too sticky, the water content is too high, and the distribution is uneven, which limits the downward growth of the main root and cannot reflect the differences between the materials. Figure 8 In Figure B, the soil moisture content was too low, the seedlings had difficulty absorbing water, the root system grew poorly, and most melon varieties could not grow normally, most of them had only short taproots. Compared with treatment three (40% moisture content), only a small number of materials were able to grow lateral roots. Under the condition of 40% moisture content ( Figure 8 (Figure C) The root system grows uniformly and the seedlings grow well and evenly.

[0102] Therefore, it can be preliminarily concluded that 40% soil moisture content is a feasible method for evaluating the differences in root growth and development of melon germplasm resources at the seedling stage.

[0103] 3.3 Root phenotypic variation of different melon germplasm resources under three water contents

[0104] Fig. 9The figure reflects the variation of taproot length, total lateral root length and number of lateral roots of 20 melon materials at 50% water content, 30% water content and 40% water content. As can be seen from the figure, the main variation range of taproot length is 15-18 cm, 12-17 cm and 16-22 cm at 50% water content, 30% water content and 40% water content, respectively; the variation range of total lateral root length is 44-60 cm, 18-46 cm and 62-108 cm, respectively; the variation range of lateral root number is 23-31, 16-30 and 32-47, respectively. Large phenotypic variation is the basis of genetic analysis. Therefore, from the perspective of the variation range of taproot length, total lateral root length and number of lateral roots, 40% soil moisture content is better than 50% and 30% water content.

[0105] 3.4 Root phenotype stability under three water contents

[0106] Correlation analysis was performed on the root phenotypes of different replicates obtained at 30%, 40% and 50% water contents, and the stability of different water content treatments was evaluated by the correlation coefficient. Figure 10-11 The figure reflects the correlation between the taproot length, total lateral root length, and number of lateral roots of 20 melon materials at 50% water content, 30% water content, and 40% water content between two replicates. We use the r value to represent the correlation coefficient between replicates, thereby showing the reproducibility of the phenotypic identification results. As can be seen from the figure, the correlation coefficient r between the taproot length measured under the three water content conditions between two replicates is 0.8352 ( Fig.10 in the figure above), -0.0161( Fig.10 ), 0.9300( Fig.10 The correlation coefficients r of the total length of lateral roots between the two replicates were 0.5157 ( Fig.11 in the upper figure), -0.0842 ( Fig.11 Figure in the middle), 0.8510( Fig.11 The correlation coefficients of lateral root number between the two replicates were 0.4022 ( Fig.12 in the figure above), -0.1646( Fig.12 Figure in the middle), 0.8844( Fig.12 Therefore, from the perspective of the reproducibility of the main root length, the total length of the lateral roots, and the number of lateral roots, 40% water content is better than 30% water content and 50% water content.

[0107] 4. Root phenotype stability under different culture conditions

[0108] The melon cultivation experiment was carried out according to the method of Example 1, and the melon seedlings were cultivated under the experimental conditions of the present invention and the normal cultivation conditions. The experimental conditions of the present invention are as follows: the temperature is 35°C, the light conditions are 3.5h light, 0.5h dark, 4h as a cycle, and the observation is started on the third day after sowing (the sowing time is the 0th day), and the pictures are taken on the 5th day after sowing as the root phenotype data. The normal cultivation conditions are: 28°C, 14h light; 25°C, 10h dark. Fig.13 This is the correlation analysis between the main root length, the number of lateral roots and the total length of lateral roots on the 5th day after sowing under the experimental conditions and the 6th day after sowing under normal conditions. It can be seen that under the two cultivation conditions, the r value of each root trait index is greater than 0.96, and the repeatability under different cultivation conditions is good. Therefore, the cultivation conditions of this experiment can shorten the cultivation and identification cycle and accelerate the experimental process without affecting the root characteristics.

[0109] 2. Determination of early growth ability of melon materials

[0110] 100 melon materials were cultured using the method of Example 1, with two replicates. The taproot length, total lateral root length and number of lateral roots were measured, and the root phenotypic variation was compared. In the experiment, the size of the acrylic box was 185×306×21 mm (internal gap 15 mm, acrylic plate thickness 3 mm, weight 370 g), and the size of the turnover box was 610*420*200 mm. Northeast black soil was selected as the soil, the total weight of the acrylic box and soil was 1300 g, and the soil filling height was 28.5 cm. The results are as follows Figure 14-15 shown.

[0111] Fig.14 The figure shows the correlation between the taproot length, total lateral root length and number of lateral roots of 100 melon materials under the cultivation method of the present invention between two replicates. As can be seen from the figure, the r value of taproot length is 0.9411 ( Fig.14 A in the figure), the r value of the total length of lateral roots is 0.8788 ( Fig.14 B), the r value of the number of lateral roots is 0.8816 ( Fig.14 C in the figure). The repeatability of the three root phenotypes under this method was above 0.85, indicating that this method has good repeatability and stability.

[0112] Fig.15 The phenotypic variation of taproot length, total lateral root length and lateral root number of 100 melon materials is shown in the figure. The horizontal axis represents two independent experimental replicates. Fig.14 It can be seen that the main root length varies from 15 to 21 cm ( Fig.15 The total length of lateral roots ranges from 52 to 103 cm ( Fig.15 The number of lateral roots ranges from 31 to 45 ( Fig.15 C in the figure). Sort the 100 materials in ascending order according to the length of the main root, the total length of the lateral roots, the number of lateral roots and the comprehensive score, such as Figure 16-19 As shown in the figure, the variation ranges of the four phenotypic characteristics are evenly distributed and continuous, and the variation differences are significant, which can distinguish the early development ability of different melons ( Figure 16-19 ).

[0113] As the length of the taproot increases, the depth of its penetration into the soil during early growth increases, which enables it to utilize moisture from deeper soil and improve drought resistance. Therefore, if the screening target is related to drought resistance, the taproot length can be used as an evaluation indicator for early growth ability.

[0114] The increase in the total length of lateral roots can expand the area of ​​the lateral roots of the plant and fix the position of the plant. Therefore, if the screening target is related to fixing the position of the plant, the total length of the lateral roots can be used as an evaluation indicator of early germination ability.

[0115] An increase in the total number of lateral roots can improve the plant's absorption of water and nutrients. Therefore, if the screening target is related to the absorption of water and nutrients, the total number of lateral roots can be used as an evaluation indicator of early germination ability.

[0116] Comprehensive score 总 It is a comprehensive evaluation after summarizing the three indicators. It is a relatively comprehensive evaluation of early flowering ability. If the screening goal is to comprehensively evaluate the early flowering ability of plants, the comprehensive score S can be used. 总 As an evaluation indicator.

[0117] Therefore, according to different screening purposes, the main root length, total lateral root length, number of lateral roots or comprehensive score S can be selected from the above indicators. 总 To evaluate the early germination ability of the tested plants.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the early root growth ability of melon seedlings, characterized in that: The following steps are involved: (1) Germination Select melon seeds that are uniform in size and plump, and germinate them until the seeds turn white; (2) Loading soil Choose cultivation boxes of the same size, punch holes in the bottom and fill them with the same amount of soil to a height of 25-30cm; adjust the soil moisture content to 40% and ensure that the moisture is evenly distributed; (3) Sowing Sow the seeds in the cultivation box and cover the surface of the seeds with soil after sowing; (4) Cultivation Place the cultivation box at an angle of 30° to the horizontal direction on the turnover box, then put the turnover box into the incubator, and place the side with the white seeds facing downward so that the roots can grow flat against the side of the cultivation box. At the same time, the side that the roots are close to is made of transparent material; no watering is required during the cultivation process; (5) Photo taking and data processing On the fifth day after sowing, take photos to obtain root system pictures, obtain data on the main root length, total lateral root length, number of lateral roots and comprehensive score of the root system, and evaluate the early root growth ability of the melon seedlings based on the obtained data; The greater the taproot length, the greater the early flowering ability of the melon; The greater the total length of the lateral roots, the greater the early germination ability of the melon; The more lateral roots there are, the stronger the early germination ability of the melon; the higher the comprehensive score, the stronger the early germination ability of the melon; The calculation method of the comprehensive score is: standardize the three indicators of main root length, total lateral root length and lateral root number, and the calculation method of the standardized value S of each indicator is: S=(XX min ) / (X max -X min ), where X is the measured value of the index of the sample to be tested, X min is the minimum value of the indicator, X max The maximum value of this indicator; the comprehensive score S 总 =S1+S2+S3, where S1, S2, and S3 are the standardized values ​​of the three indicators: main root length, total lateral root length, and lateral root number, respectively.

2. A method for evaluating the early root growth ability of melon seedlings according to claim 1, characterized in that: In the step (2), the length, height and width of the cultivation box are 185×306×21 mm, and there is a gap of at least 15 mm in width inside the box to accommodate the growth of the seed roots; the white end of the seed faces the side formed by the length and height of the cultivation box; during the sowing process, the white end of the seed is kept at the same distance from the side of the cultivation box.

3. A method for evaluating the early root growth ability of melon seedlings as claimed in claim 1, characterized in that In the step (2), the soil moisture content is measured by weighing a certain weight of soil and placing it in an oven to dry it to a constant weight. The soil moisture content = (soil weight before drying - soil weight after drying) / soil weight after drying. In the step (2), a hole with a diameter of 0.5 cm is uniformly punched in the middle of the bottom of the cultivation box.

4. A method for evaluating the early root growth ability of melon seedlings as claimed in claim 1, characterized in that In the step (2), the soil is black soil, the weight of the black soil in each cultivation box is 900-1000g, and the soil filling height is 28.5 cm; in the step (3), after sowing, the surface of the seeds is covered with 1 cm of soil.

5. The method for evaluating the early root growth ability of melon seedlings according to claim 1, characterized in that: In the step (4), the temperature in the incubator is set at 35°C, the humidity is 40-50%, the light cycle is 3.5 hours of light treatment and 0.5 hours of dark treatment, and 6 cycles are performed per day.

6. A method for evaluating the early root growth ability of melon seedlings according to claim 1, characterized in that: In the step (5), ImageJ software is used to process the root system image to determine the main root length, the total length of the lateral roots and the number of lateral roots.

7. Application of the evaluation method as described in any one of claims 1 to 6 in distinguishing the early growth ability of melon.

8. The use according to claim 7, characterized in that In the application, the evaluation method measures the taproot length, total lateral root length, number of lateral roots and comprehensive score of the melon; the longer the taproot is, the stronger the early growth ability of the melon is; The greater the total length of the lateral roots, the greater the early germination ability of the melon; The more lateral roots there are, the stronger the early germination ability of the melon; the higher the comprehensive score, the stronger the early germination ability of the melon.

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