Method for identifying sensitivity of cotton to thidiazuron defoliating agent

Abstract

The invention discloses a method for identifying the sensitivity of cotton to a thidiazuron defoliating agent, which comprises the following steps of: (1) spraying the thidiazuron defoliating agent to cotton plants in a test field in a boll opening period of the cotton; (2) on the spraying day, measuring the leaf area index of the test cotton plant and counting the leaf number of the test cotton plant; (3) counting the number of leaves of the test cotton plant and measuring the soluble sugar content and the ethylene release amount of the functional leaves of the main stem at the top of the test cotton plant in the fifth day after spraying; (4) calculating the defoliation rate of the fifth day by using the statistical values in the steps (2) and (3), comparing the defoliation rate of the fifth day and the measured leaf area index, soluble sugar content and ethylene release amount values with standard values, and then scoring; and (5) determining the sensitivity of the cotton to the defoliating agent according to the comprehensive fraction of the defoliating rate, the leaf area index, the soluble sugar content and the ethylene release amount on the fifth day.

Description

Technical Field

[0001] The invention belongs to the field of agricultural biotechnology, and in particular relates to a method for identifying the sensitivity of cotton to a thidiazuron defoliant. Background Art

[0002] With the development of my country's economy and the continuous improvement of mechanized cotton production technology, mechanical picking is gradually replacing manual picking and becoming the mainstream direction of cotton production development. For example, mechanical picking has been realized on a large scale in Xinjiang cotton-growing areas in my country, and is being gradually promoted in other cotton-growing areas. Mechanical picking can effectively reduce labor costs and improve the benefits of cotton planting. In order to ensure the time and economic efficiency of mechanical picking, mechanical picking requires not only cotton picking machinery, but also a combination of suitable cotton varieties and their cultivation measures. Among them, chemical defoliation is a necessary link and important prerequisite for mechanical picking. Spraying defoliants is a key link in improving the quality and efficiency of cotton. Using defoliants for chemical defoliation can cause most of the leaves of cotton plants to fall off, reduce the impurity content in mechanically harvested seed cotton and the pollution of cotton leaves to cotton fibers. After defoliation, the mildew rate of cotton bolls at the bottom of the cotton plant can be reduced, while accelerating the cotton bolls to open and increase the pre-frost flowering rate.

[0003] At present, the defoliant with thidiazuron as the main ingredient is commonly used in machine-picked cotton fields. It is a new type of highly efficient physiologically regulated defoliant that can promote biochemical reactions in cotton, causing abscission at the base of cotton petioles and leaf shedding. The effect of defoliants is closely related to cotton varieties. Different varieties have different responses to defoliants. In production, some cotton varieties are slow to respond to defoliants. After spraying defoliants, the defoliation rate does not meet the standard (defoliation rate ≤ 90%), which affects the effect of mechanical picking. Therefore, it is necessary to evaluate and identify the sensitivity of cotton to thidiazuron defoliant.

[0004] Among the methods of the prior art, some are based on whether the defoliation rate after spraying the defoliant can meet the picking requirements for 15 days, but this method takes a long time, and the defoliation effect is greatly affected by the weather, which can easily interfere with the judgment; if the effect is not good, time does not allow remedial measures to be taken; there are also methods that use the relationship between the soluble sugar content in the cotton leaves after spraying the defoliant and the cotton defoliation rate to characterize the sensitivity, but the soluble sugar content is greatly affected by factors such as fertilizer, water and temperature. Therefore, the use of soluble sugar content for characterization often results in large deviations in practice, that is, a single indicator cannot accurately judge the sensitivity of cotton varieties to the thidiazuron defoliant.

[0005] In view of the above-mentioned deficiencies in the prior art, it is particularly necessary to study a method that is feasible in practice and can more accurately characterize the sensitivity of cotton to the thidiazuron defoliant. Summary of the invention

[0006] In the study of the sensitivity of cotton to thidiazuron defoliant, the inventor explored the relationship between cotton morphological indexes, physiological indexes, hormone indexes, etc. and the shedding rate, and found that the cotton leaf area index and ethylene release were positively correlated with the defoliation rate. The defoliation rates of different varieties reached significant differences on the 5th day after spraying the defoliant and were positively correlated with the defoliation rate. The leaf area index is an important indicator of the external morphology of plants. It reflects the growth status of plant populations, and its size is directly closely related to the final yield. Ethylene is an important plant endogenous hormone and plays an important role in the shedding of plant organs. It can promote the synthesis of cellulase, a cell wall degrading enzyme, and control the release of cellulase from protoplasts into the cell wall, thereby promoting cell aging and cell wall decomposition, causing the cell expansion near the stem side of the abscission zone, thereby forcing leaves, flowers or fruits to mechanically detach. In addition, soluble sugar is an important physiological and biochemical indicator in plants, and sugar metabolism can reflect the sensitivity of cotton to defoliants to a certain extent. The study found that the soluble sugar content in cotton leaves after spraying defoliants was negatively correlated with the cotton defoliation rate. Adding negatively correlated characterization parameters in the evaluation process can more scientifically, comprehensively and accurately reflect the sensitivity of cotton to the thidiazuron defoliant.

[0007] Based on the above research, the present invention proposes to use leaf area index, soluble sugar content, ethylene release and defoliation rate on the 5th day after spraying defoliants as identification indicators, gives reference values ​​and scoring standards for each indicator, and conducts comprehensive characterization, which can scientifically and accurately determine the sensitivity of cotton varieties to defoliants.

[0008] More specifically, according to an embodiment of the present invention, there is provided a method for identifying the sensitivity of cotton to the thidiazuron defoliant, comprising the following steps:

[0009] (1) During the cotton boll opening period, the cotton plants in the experimental field were sprayed with the defoliant Thidiazuron-methyl;

[0010] (2) On the day of spraying, the leaf area index of the test cotton plants was measured and the number of leaves of the test cotton plants was counted;

[0011] (3) On the 5th day after spraying, the number of leaves of the test cotton plants was counted, and the soluble sugar content and ethylene release of the functional leaves on the top main stem of the test cotton plants were measured;

[0012] (4) calculating the defoliation rate on the 5th day using the statistical values ​​of steps (2) and (3), and comparing the defoliation rate on the 5th day and the measured leaf area index, soluble sugar content and ethylene release values ​​with the standard values, and then scoring; and

[0013] (5) Determine the sensitivity of cotton to the defoliant based on the comprehensive score of defoliation rate, leaf area index, soluble sugar content and ethylene release on the 5th day.

[0014] According to an embodiment of the present invention, the method further comprises, after step (5) and before mechanically picking the cotton, counting the number of leaves of the test cotton plants, calculating the actual defoliation rate, and verifying the judgment of the sensitivity of the cotton to the defoliant in step (5).

[0015] According to an embodiment of the present invention, on the 20th day after spraying, the number of leaves of the test cotton plants is counted to calculate the actual defoliation rate.

[0016] According to an embodiment of the present invention, in step (1), the thidiazuron defoliant is thidiazuron 50% wettable powder, and the spraying amount is 40-60 g / mu.

[0017] According to the embodiment of the present invention, the leaf number is counted by manual survey method, and 20-30 cotton plants with normal growth in the test field are randomly selected for counting.

[0018] According to an embodiment of the present invention, the ethylene release is measured by gas chromatography, the soluble sugar content is measured by anthrone colorimetry, and the leaf area index is measured by a canopy meter field measurement method.

[0019] According to an embodiment of the present invention, in step (4), the standard value and the scoring method are as follows:

[0020] Leaf area index ≥4.0, 5 points; [3.5, 4.0), 3 points; <3.5, 1 point;

[0021] Soluble sugar content mg·g －1 ≤7.0, 5 points; (7.0, 9.0], 3 points; >9.0, 1 point;

[0022] Ethylene release uL.g -1 .h -1 ≥25.0, 5 points; [22.0, 25.0), 3 points; <

[0023] 22.0, 1 point;

[0024] On the 5th day, if the leaf removal rate % ≥ 65.0%, 5 points; [55.0, 65.0), 3 points; < 55.0, 1 point;

[0025] A total score of >18 points is considered as high sensitivity; a total score of 15-18 points is considered as acceptable sensitivity; a total score of <15 points is considered as poor sensitivity.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention adopts multi-index comprehensive characterization, changes the single basis for determining sensitivity into multi-index identification, and adopts positively correlated and negatively correlated indicators, and adopts different exogenous and endogenous indicators, thereby greatly reducing the uncertainty caused by climate environment, individual differences of organisms, etc., making the identification more scientific and accurate;

[0028] The technology of the present invention can also be used to predict the defoliation effect of mechanically harvested cotton fields in advance, and timely arrange remedial measures to avoid problems such as high impurity rate, large loss rate, and incomplete harvesting caused by poor defoliation effect.

[0029] This technology can be used to accurately identify the sensitivity of cotton to the defoliant thidiazuron, effectively select varieties that are sensitive to defoliants, eliminate insensitive strains, save time and energy, and improve breeding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a schematic diagram of a method for identifying the sensitivity of cotton to the defoliant thidiazuron according to an embodiment of the present invention.

[0031] Specific implementation process

[0032] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. The shown contents are used to fully illustrate the contents of the present invention, but are not used to limit the present invention.

[0033] Figure 1 Schematic diagram of a method for identifying the sensitivity of cotton to thidiazuron defoliant according to an embodiment of the present invention. As shown in the figure, the method for identifying the sensitivity of cotton to thidiazuron defoliant may include the following steps:

[0034] First, the cotton strain (variety) to be identified can be planted in the test field, and when the cotton grows to the boll opening stage, the cotton plants in the test field can be sprayed with a thidiazuron defoliant, for example, the defoliant can be a thidiazuron 50% wettable powder, and the application amount can be 40-60 g / mu. The defoliant can be dissolved in water and sprayed evenly, for example, 20-30 g of a thidiazuron 50% wettable powder can be weighed and dissolved in 15 L of water, and the specific application amount can be selected according to the growth requirements of the cotton.

[0035] On the day of spraying, the leaf area index of the test cotton plants can be measured and the number of leaves (A) of the test cotton plants can be counted. For example, the test and statistics can be carried out before spraying the defoliant, or shortly after spraying the defoliant. The leaf area index is a comprehensive indicator of the vegetation's light energy utilization and canopy structure. It is also an important indicator reflecting the external morphology of the plant and the growth status of the plant population. Studies have found that the leaf area index may be related to the absorption of the defoliant, and the leaf area index is significantly positively correlated with the shedding rate.

[0036] The leaf area index can be selected from the group leaf area index, for example, the field measurement method of the LAI-2200 canopy meter can be used, and 5 points are selected in a "z" shape and the average is taken. The number of leaves is counted by manual investigation, and 20-30 cotton plants with normal growth in the test field are selected for statistics, and the number of leaves per plant is investigated and the average is taken.

[0037] On the 5th day after spraying, the number of leaves of the cotton plants selected in the previous step was counted (B), and the soluble sugar content and ethylene release of the functional leaves on the top main stem of the test cotton plants were measured.

[0038] In this step, the number of leaves of the cotton plants selected in the previous step is counted, and then combined with the counted value on the day of spraying, the defoliation rate on the 5th day can be calculated. The calculation method of the defoliation rate is as follows: defoliation rate (%) = (number of leaves on the day of spraying - number of leaves on the 5th day after spraying) / number of leaves on the day of spraying × 100.

[0039] The existing technology generally uses the defoliation rate after 15 days or more to reflect the defoliation effect of the defoliant. However, in practice, the time for applying defoliants is mostly during the boll-opening period; after 15 days or more, if the defoliation effect is found to be poor, it is difficult to remedy it, because it is too late to apply other defoliants at this time and the effect is also poor. Studies have shown that the defoliation rate of different varieties reaches a significant difference on the 5th day after spraying the defoliant and is positively correlated with the defoliation rate, that is, the defoliation rate on the 5th day can also reflect the defoliation effect of the defoliant. This can greatly shorten the identification time of the defoliation effect and is beneficial to taking remedial measures.

[0040] Soluble sugar is the basis of plant metabolism and plays an important role in plant growth and development. Sugar metabolism can reflect the sensitivity of cotton to defoliants to a certain extent. Studies have found that the soluble sugar content in cotton leaves after spraying defoliants is negatively correlated with the defoliation rate of cotton.

[0041] The soluble sugar content can be tested by anthrone colorimetry. The specific method includes: weigh 0.1g of leaves, put them into a glass test tube, add 8ml of 85% ethanol, seal it, extract in boiling water for 30min, extract 3 times, filter the extract into a 25ml volumetric flask, and dilute to the scale to obtain a soluble sugar extract. Take 0.5ml of the sample extract, add 1.5ml of distilled water to the test tube, then add 0.5ml of anthrone ethyl acetate reagent and 5ml of concentrated sulfuric acid to the test tube in sequence, shake it thoroughly, immediately put the test tube into a boiling water bath, keep it warm for 1min, then take it out, use a blank as a control, cool it naturally to room temperature, and measure its absorbance at a wavelength of 630nm. The soluble sugar content is calculated by the standard linear equation. Different samples can be selected, and the average value can be obtained by multiple measurements.

[0042] Ethylene is an important plant endogenous hormone, which plays an important role in plant organ shedding. It can promote the synthesis of cell wall degrading enzymes - cellulase and control the release of cellulase from protoplasts into the cell wall, thereby promoting cell aging and cell wall decomposition, causing the cells near the stem side of the abscission zone to swell, thereby forcing leaves, flowers or fruits to mechanically detach. Studies have found that the amount of ethylene released is positively correlated with the defoliation rate. The amount of ethylene released can be detected by gas chromatography. The specific method includes: taking 0.5g of leaves and placing them in a penicillin bottle of known volume, sealed with a rubber stopper. Place them at room temperature (27℃) away from light for 24 hours, and use a syringe to extract 1ml of gas from the bottle and inject it into the gas chromatograph to determine the ethylene concentration. Different samples can be selected, and the average value can be obtained by multiple measurements.

[0043] Then, the defoliation rate, leaf area index, soluble sugar content and ethylene release values ​​on the 5th day are compared with the standard values ​​and scored; and the sensitivity of cotton to the defoliant is determined based on the comprehensive score of the defoliation rate, leaf area index, soluble sugar content and ethylene release on the 5th day.

[0044] The standard values ​​and scoring methods are shown in Table 1 below:

[0045] Table 1: Scoring method and criteria

[0046]

[0047] Finally, the method of the present invention may include a verification step, for example, after spraying the defoliant and before mechanically picking the cotton, the number of leaves of the test cotton plant can be counted to calculate the actual defoliation rate. For example, the number of leaves of the cotton plant can be counted on the 15th day and the 20th day after spraying the defoliant. The calculated defoliation rate is compared with the sensitivity result of the cotton to the defoliant identified in the method of the present invention, so as to perform verification.

[0048] The present invention adopts different endogenous parameter indicators such as ethylene as a hormone and soluble sugar as a metabolite, and different external parameter indicators such as leaf area index and leaf removal rate on the 5th day. At the same time, these indicators include a combination of positively correlated indicators (leaf area index, leaf removal rate on the 5th day, ethylene release) and negatively correlated indicators (soluble sugar content), which can greatly reduce the uncertainty caused by climate environment, individual differences of organisms, etc., and make identification more scientific and accurate.

[0049] In order to further verify the method of the present invention, the present invention conducted a field test on 15 cotton lines, as follows:

[0050] Test subjects: 15 high-generation stable cotton lines

[0051] Test indicators: leaf area index, soluble sugar content, ethylene release, leaf loss rate on the 5th day, leaf loss rate on the 20th day

[0052] Test method: adopt a planting pattern with equal row spacing of 76 cm and a planting density of 6000 plants / mu; spray thidiazuron defoliant (thidiazuron 50% wettable powder, 25g diluted with 15L of water, dosage is 30L / mu) on September 20, 2023, and spray evenly; the leaf area index is determined by LAI-2200 canopy meter; the soluble sugar content is determined by anthrone reagent method (five samples are averaged); ethylene release is determined by GC-

[0053] The determination was carried out by 9800 gas chromatograph (the average of five samples was taken); the defoliation rate was determined by manually investigating the number of leaves (30 plants); the identification and scoring methods are shown in Table 1.

[0054] The test results are shown in Table 2 below:

[0055] Table 2: Test results

[0056]

[0057] As can be seen from the above table, according to the determination data and selection criteria, the total scores of each index of strains 15-1166, 12-1613, and 12-1458 were greater than 18 points, which are strains with strong sensitivity to defoliants; the total scores of each index of strains 13-1781, 16-1252, and 14-1472 were greater than 15 points, which are qualified strains with sensitivity to defoliants; and the others are strains with poor sensitivity to defoliants. And the statistical value of the defoliation rate % on the 20th day is basically consistent with the above conclusion, which verifies the scientificity and accuracy of the method of the present invention. In addition, the test results also show that some strains have a higher score for a single index, but the overall score is low, and the final defoliation effect is not ideal, which also reflects the uncertainty of using a single indicator for characterization.

[0058] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for identifying the sensitivity of cotton to the defoliant thidiazuron, characterized in that: The steps include: (1) During the cotton boll opening period, the cotton plants in the experimental field were sprayed with the defoliant Thidiazuron; (2) On the day of spraying, the leaf area index of the test cotton plants was measured and the number of leaves of the test cotton plants was counted; (3) On the 5th day after spraying, the number of leaves of the test cotton plants was counted and the soluble sugar content and ethylene release of the functional leaves on the top main stem of the test cotton plants were measured; (4) calculating the defoliation rate on the 5th day using the statistical values ​​of steps (2) and (3), and comparing the defoliation rate on the 5th day and the measured leaf area index, soluble sugar content and ethylene release values ​​with the standard values, and then scoring; and (5) Determine the sensitivity of cotton to the defoliant based on the comprehensive score of defoliation rate, leaf area index, soluble sugar content and ethylene release on the 5th day.

2. The method according to claim 1, characterized in that The method also includes, after step (5) and before mechanically picking the cotton, counting the number of leaves of the test cotton plants, calculating the actual defoliation rate, and verifying the judgment of the sensitivity of the cotton to the defoliant in step (5).

3. The method according to claim 2, characterized in that On the 20th day after spraying, the number of leaves of the test cotton plants was counted and the actual defoliation rate was calculated.

4. The method according to claim 1, characterized in that: In step (1), the thidiazuron defoliant is thidiazuron 50% wettable powder.

5. The method according to claim 1, characterized in that The leaf number was counted by manual survey, and 20-30 cotton plants growing normally in the test field were randomly selected for counting.

6. The method according to claim 1, characterized in that The ethylene emission was measured by gas chromatography, the soluble sugar content was measured by anthrone colorimetry, and the leaf area index was measured by canopy meter field measurement method.

7. The method according to claim 1, characterized in that In step (4), the standard value and scoring method are as follows: Leaf area index ≥4.0, 5 points; [3.5, 4.0), 3 points; <3.5, 1 point; Soluble sugar content mg·g －1 ≤7.0, 5 points; (7.0, 9.0], 3 points; >9.0, 1 point; Ethylene release uL.g -1 .h -1 ≥25.0, 5 points; [22.0, 25.0), 3 points; < 22.0, 1 point; On the 5th day, if the leaf removal rate % ≥ 65.0%, 5 points; [55.0, 65.0), 3 points; < 55.0, 1 point; A total score of >18 points is considered as high sensitivity; a total score of 15-18 points is considered as acceptable sensitivity; a total score of <15 points is considered as poor sensitivity.

8. The method according to claim 3, characterized in that The application rate of thidiazuron 50% wettable powder is 40-60g / mu.

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