Seed coating agent for corn seed coating as well as preparation method and application of seed coating agent

Abstract

The invention belongs to the technical field of seed coating agents, and particularly relates to a seed coating agent for corn seed coating as well as a preparation method and application thereof. The seed coating agent for corn seed coating provided by the invention is prepared from the following raw materials in concentration: 0.75 wt%-2.5 wt% of chitosan, 50-75 [mu] mol / L of melatonin and 0.2 wt%-0.4 wt% of acetic acid. Chitosan and melatonin are combined for use and can play an effective synergistic role, so that the adaptive capacity of the corn seeds under normal conditions or salt stress conditions is enhanced, the germination rate of the corn seeds is remarkably increased, and the growth of corn seedlings and the increase of crop yield are promoted. Therefore, the invention can provide a technical theoretical basis for development of a corn seed coating agent, improvement of film-forming performance, promotion of seed germination, reduction of pollution, improvement of crop yield and the like, and has a wide application prospect in the field of corn seed coating.

Description

Technical Field

[0001] The invention belongs to the technical field of seed coating agents, and particularly relates to a seed coating agent for corn seed coating, a preparation method and application thereof. Background Art

[0002] Corn is one of the three major grain crops in my country and an important source of feed for industries such as animal husbandry and breeding. In addition, corn is one of the indispensable raw materials for industries such as food processing and brewing. Therefore, achieving a stable growth in corn production is of great significance to meet the development needs of industries such as food, animal husbandry, and breeding. However, the growth and development of corn is easily affected by adverse factors such as drought, low temperature, and especially salinity-alkali stress, which greatly reduces the germination rate and yield of corn.

[0003] In recent years, the use of seed coating agents to coat crops has become an emerging means in the industry to increase crop yields. Seed coating agents are pesticide preparations used for treating crop or other plant seeds. They have film-forming properties and are usually made from pesticide raw materials (such as insecticides, fungicides, hormones and seed fertilizers, etc.), film-forming agents, wetting agents, dispersants, penetrants and other additives. Seed coating agents can be coated on the surface of seeds directly or after dilution to form a protective film with certain strength and permeability. In addition, seed coating agents form a protective layer on the surface of seeds, thereby promoting the growth of crops and increasing crop yields; killing underground pests and seedling pests, preventing and controlling seedling diseases and systemic diseases; improving seed germination rate, promoting healthy growth of seedlings, and reducing seed usage.

[0004] However, most existing seed dressing agents have the disadvantages of complex raw material types, cumbersome preparation, and unstable properties and efficacy. In addition, most seed dressing agents inevitably require the use of chemical agents. If the seed dressing agents are used excessively or improperly, pesticide residues may result. These residues will gradually seep into the soil and water sources, and have a negative impact on the ecosystem. Moreover, at this stage, there are many types of seed dressing agents, and they cannot be directly applied between different crops. If inappropriate seed dressing agents are used for specific crops, they may inhibit the normal germination of seeds and reduce crop yields.

[0005] For corn seed coating, the existing technology still lacks a seed coating agent formula that can effectively improve the germination rate and salt stress resistance of corn seeds. Therefore, it is very important to develop a special seed coating agent for corn seeds that has a simple composition, is environmentally friendly, and has good safety. Summary of the invention

[0006] In order to overcome the deficiencies in the prior art, the first aspect of the present invention is to provide a seed coating agent for corn seed coating, which is suitable for coating corn seeds and can effectively improve the germination of corn seeds under normal conditions or salt stress conditions.

[0007] The second aspect of the present invention is to provide a method for preparing the seed coating agent for corn seed coating.

[0008] The third aspect of the present invention is to provide the use of the seed coating agent for corn seed coating.

[0009] To achieve the above object, in the first aspect of the present invention, the technical solution adopted is:

[0010] A seed coating agent for corn seed coating is composed of raw materials with the following concentrations: 0.75wt%-2.5wt% chitosan, 50-75μmol / L melatonin, and 0.2wt%-0.4wt% acetic acid.

[0011] As a preferred solution, when the seed coating agent is used for coating corn seeds under normal conditions, the concentration of chitosan is 0.75 wt % and the concentration of melatonin is 75 μmol / L.

[0012] As a preferred solution, when the seed coating agent is used for coating corn seeds under salt stress conditions, the concentration of chitosan is 2.5 wt % and the concentration of melatonin is 50 μmol / L.

[0013] The second aspect of the present invention adopts the technical solution as follows:

[0014] The preparation method of the seed coating agent for corn seed coating comprises the following steps:

[0015] The chitosan is mixed in the acetic acid solution to obtain a chitosan solution; melatonin is mixed in water to obtain a melatonin solution; the chitosan solution and the melatonin solution are mixed evenly to obtain the seed coating agent.

[0016] As a preferred solution, the concentration of the chitosan solution is 1.5wt% to 5wt%; the concentration of the melatonin solution is 100 to 150 μmol / L.

[0017] As a preferred solution, the concentration of the acetic acid solution is 0.4wt% to 0.8wt%.

[0018] As a preferred solution, the mixing volume ratio of the chitosan solution to the melatonin solution is 1:1.

[0019] As a preferred solution, the concentration of the chitosan solution is 1.5wt%; the concentration of the melatonin solution is 150μmol / L. The seed coating agent obtained under this concentration ratio can effectively improve the germination of corn seeds under normal conditions.

[0020] As a preferred solution, the concentration of the chitosan solution is 5wt%; the concentration of the melatonin solution is 100 μmol / L. The seed coating agent obtained under this concentration ratio can effectively improve the germination of corn seeds under salt stress conditions.

[0021] In the third aspect of the present invention, the technical solution adopted is:

[0022] The application of the seed coating agent for corn seed coating is to coat corn seeds with the seed coating agent to enhance the germination of corn seeds under normal conditions or salt stress.

[0023] As a preferred solution, the amount of coated corn seeds used is 80-120 g per 10 mL of seed coating agent.

[0024] The technical solution of the present invention has the following advantages and beneficial effects:

[0025] (1) Chitosan (CS) is a natural polysaccharide, which is mainly obtained by deacetylation of chitin. In nature, chitosan can be decomposed by biological enzymes, and its degradation products are environmentally friendly. Melatonin (MT) is a multifunctional neuroendocrine lipid-soluble small molecule, which is mainly secreted by the pineal gland and widely present. Both CS and MT are used in medicine, food, agriculture, environmental protection and other fields.

[0026] In the present invention, chitosan and melatonin are used in combination in the coating of corn seeds. The two can effectively replace traditional chemical pesticides as raw materials. They are not only biodegradable, environmentally friendly, non-toxic and safe, but also have a small number of raw material types and low production costs. After the two are combined, they can effectively meet the comprehensive requirements of the corn seed coating agent for film-forming property, pH, compatibility, coating film-forming time and coating qualified rate on the basis of simplifying the raw material composition.

[0027] (2) The present invention uses chitosan and melatonin in combination, and the two can play an effective synergistic role. The protective film of chitosan helps to stabilize and slowly release melatonin around the seeds, while melatonin enhances the biological activity of chitosan, thereby significantly enhancing the adaptability of corn seeds under normal conditions or salt stress conditions, significantly improving the germination rate of corn seeds, and further promoting seedling growth and increasing crop yields.

[0028] Therefore, the present invention uses chitosan combined with melatonin to coat corn seeds, which can provide a technical theoretical basis for the development of corn-specific seed coating agents and the improvement of film-forming properties, promote seed germination, reduce pollution, and increase crop yields, and has broad application prospects in the field of corn seed coating. DETAILED DESCRIPTION

[0029] The technical scheme and technical effects of the present invention will be clearly and completely described below in conjunction with specific embodiments and test examples. However, it should be understood by those skilled in the art that the embodiments are only used to illustrate the technical scheme of the present invention and should not be regarded as limiting the scope of protection of the present invention. The test methods used in the following examples are conventional methods unless otherwise specified; the raw materials used are all commonly used in the art, available to the public or commercially available, unless otherwise specified.

[0030] In the following examples, the chitosan used has a deacetylation degree of ≥95% and a viscosity of 100-200 mPa·s; and the melatonin comes from a conventional commercial brand.

[0031] Example 1

[0032] This embodiment provides a seed coating agent for corn seed coating, which is composed of raw materials with the following concentrations: chitosan 0.75wt%, melatonin 75μmol / L, acetic acid 0.3wt%. The seed coating agent is suitable for corn seed coating under normal conditions.

[0033] The preparation method of the seed coating agent for corn seed coating comprises the following steps:

[0034] Chitosan was mixed in an acetic acid solution (acetic acid concentration 0.6wt%) to obtain a chitosan solution (concentration 1.5wt%); melatonin was mixed in water to obtain a melatonin solution (concentration 150μmol / L); the chitosan solution and the melatonin solution were mixed in a volume ratio of 1:1 to obtain the seed coating agent of Example 1. In the seed coating agent prepared in Example 1, the chitosan concentration was 0.75wt%, and the melatonin concentration was 75μmol / L.

[0035] Example 2

[0036] This embodiment provides a seed coating agent for corn seed coating, which is composed of raw materials with the following concentrations: 2.5wt% chitosan, 50μmol / L melatonin, and 0.3wt% acetic acid. The seed coating agent is suitable for corn seed coating under salt stress conditions.

[0037] The preparation method of the seed coating agent for corn seed coating comprises the following steps:

[0038] Chitosan was mixed in an acetic acid solution (acetic acid concentration 0.6wt%) to obtain a chitosan solution (concentration 5wt%); melatonin was mixed in water to obtain a melatonin solution (concentration 100μmol / L); the chitosan solution and the melatonin solution were mixed in a volume ratio of 1:1 to obtain the seed coating agent of Example 2. In the seed coating agent prepared in Example 2, the chitosan concentration was 2.5wt%, and the melatonin concentration was 50μmol / L.

[0039] Experimental Example 1: Effects of Chitosan Coating at Different Concentrations on Corn Seed Germination

[0040] Weigh 0.5g, 1.0g, 1.5g, 2.0g, 2.5g and 3g of chitosan powder respectively, put them in 6 small beakers, numbered 1 to 6, add 0.6wt% acetic acid solution, make the volume to 100mL, and stir continuously with a glass rod to accelerate dissolution, and prepare chitosan solutions with concentrations of 0.5%, 1%, 1.5%, 2%, 2.5% and 3% for stand-alone use.

[0041] Select corn seeds of uniform size and free of pests and diseases, disinfect them with 1.0% sodium hypochlorite for 10 minutes, rinse them with distilled water for 3-5 times, and air-dry them for use. Add corn seeds to the chitosan solution according to the dosage of coating 100g corn seeds per 10mL chitosan solution, stir with a glass rod for 5-6 minutes, and after all the seeds are evenly coated with the seed coating agent, continue to stir for 5-10 minutes according to the different coating concentrations until the seed surface solidifies into a film and the seeds do not stick to each other or clump, spread the seeds on clean germination paper and move them to a 25℃ forced air drying oven to dry for 48 hours.

[0042] Place the coated seeds in a clean germination box, evenly place 40 seeds in each germination box, and place them in an artificial climate incubator (25℃, 16h light; 20℃, 8h dark, humidity 65%-80%) for germination test. The uncoated seeds were used as the control group (CK), and three replicates were set for each treatment. The number of germinations was counted at a fixed time every day, and the germination potential, germination rate, germination index, vitality index, average germination time and other indicators were calculated. Among them, germination rate (GR) = (total number of germinated seeds / total number of seeds) × 100%. Germination potential (GP) = (number of seeds germinated on the second day / total number of test seeds) × 100%. Average germination time (MGT) = ∑ (Gt×Dt) / ∑Gt; germination index (GI) = ∑ (Gt / Dt), where Gt is the total number of seeds germinated per day, and Dt is the corresponding number of germination days. Seedling length (S): After 7 days of seed germination, 5 seedlings were taken from each germination box to measure their seedling lengths, and the results were averaged. Vitality index (VI) = S × GI, S refers to the seedling height measured on the 7th day. The test results of different concentrations of chitosan coating on corn seed germination are shown in Table 1.

[0043] Table 1. Effects of different concentrations of chitosan coating on corn seed germination

[0044] deal with Germination rate / % Germination potential / % Germination days / d Germination Index Seedling length / cm Vitality Index CK <![CDATA[73±2.5 c ]]> <![CDATA[32±10.10 d ]]> <![CDATA[2.70±0.24 a ]]> <![CDATA[11.45±0.62 c ]]> <![CDATA[2.80±0.00 d ]]> <![CDATA[33.13±1.30 d ]]> 0.5％ <![CDATA[83±2.89 ab ]]> <![CDATA[38±1.44 cd ]]> <![CDATA[2.74±0.20 a ]]> <![CDATA[13.16±0.52 b ]]> <![CDATA[3.60±0.36 c ]]> <![CDATA[41.14±5.66 c ]]> 1.0％ <![CDATA[84±3.82 ab ]]> <![CDATA[36±1.44 cd ]]> <![CDATA[2.73±0.08 a ]]> <![CDATA[13.20±0.36 b ]]> <![CDATA[3.53±0.23 c ]]> <![CDATA[42.63±4.16 bc ]]> 1.5％ <![CDATA[85±2.50 a ]]> <![CDATA[49±6.29 bc ]]> <![CDATA[2.55±0.13 ab ]]> <![CDATA[14.28±0.22 a b]]> <![CDATA[4.53±0.32 a ]]> <![CDATA[61.85±3.79 a ]]> 2.0％ <![CDATA[83±3.82 ab ]]> <![CDATA[48±10.90 c ]]> <![CDATA[2.56±0.15 ab ]]> <![CDATA[13.93±1.09 ab ]]> <![CDATA[4.23±0.31a b ]]> <![CDATA[57.28±4.44 a ]]> 2.5％ <![CDATA[79±1.44 ab ]]> <![CDATA[64±7.27 a ]]> <![CDATA[2.19±0.09 c ]]> <![CDATA[14.83±0.60 a ]]> <![CDATA[3.90±0.40b c ]]> <![CDATA[49.73±5.41 b ]]> 3.0％ <![CDATA[78±3.82 b ]]> <![CDATA[62±7.64 ab ]]> <![CDATA[2.32±0.18 bc ]]> <![CDATA[14.30±1.27 ab ]]> <![CDATA[3.83±0.31b c ]]> <![CDATA[48.66±1.95 bc ]]>

[0045] As shown in Table 1, the germination of corn seeds was significantly promoted after coating with chitosan solutions of different concentrations. However, with the increase of chitosan concentration, germination first increased, reaching the highest at 1.5%, and then decreased, showing an obvious concentration effect. The 1.5% chitosan concentration coating had the best promoting effect on the germination of corn seeds, and performed best in terms of germination rate, germination potential, germination index and vitality index. The germination rate was 85%, which was significantly increased by 12% compared with the control. After exceeding the concentration of 1.5%, some indicators such as germination rate and vitality index decreased, which may indicate that excessive chitosan concentration has an inhibitory effect on seed germination. Therefore, 1.5% was selected as the optimal chitosan coating concentration for subsequent experiments.

[0046] Experimental Example 2: Effect of Chitosan and Melatonin on Corn Seed Germination

[0047] In a light-proof environment, take 1.16 mg, 2.23 mg, 3.48 mg, 4.64 mg, and 5.81 mg of melatonin powder (MT), add distilled water and stir until completely dissolved, and make the volume to 100 mL to obtain melatonin solutions with concentrations of 50, 100, 150, 200, and 250 μmol / L, respectively.

[0048] According to the optimal chitosan concentration (CS, concentration 1.5wt%) screened out by the above test results, the chitosan solution was mixed with the melatonin solution at a volume ratio of 1:1 in a light-proof environment, and the composite coating agents of different concentrations were obtained after stirring evenly.

[0049] The coating method and seed culture method are the same as those in Experimental Example 1. Uncoated corn seeds are used as the control group (CK), chitosan-coated seeds are used as the comparison group, and different concentrations of composite coating agents are used as treatment groups. Three replicates are set for each treatment, and corn seeds are cultured under normal culture conditions. The number of germinations is counted at a fixed time every day, and the germination potential, germination rate, germination index, vitality index, and average germination time are calculated. The results are shown in Table 2.

[0050] Table 2 Effects of 1.5% chitosan + different concentrations of melatonin coating on corn seed germination

[0051]

[0052] It can be seen from the test results in Table 2 that under normal culture conditions, the composite seed coating agent obtained by further adding melatonin to chitosan has a significant promoting effect on seed germination. Compared with the single chitosan coating group, when the melatonin concentration was 100-200 μmol / L combined with chitosan coating, the germination index had a significant promoting effect. When the concentration reached 250 μmol / L, the germination rate decreased. With the increase of melatonin concentration, the germination rate showed a trend of first increasing and then decreasing. Among them, the germination index of the CS (1.5) + MT150 treatment group was the highest, and the germination rate, germination potential, germination index, seedling length and vitality index increased by 5%, 15%, 19%, 3% and 19% respectively. Although the average germination time of the coating treatment was delayed compared with the control, this method significantly improved the seed emergence rate and survival rate. Therefore, the coating treatment helps to resist the influence of pathogens and adverse environmental factors in the soil by providing a protective layer, thereby ensuring the health of seeds in the early germination stage.

[0053] Test Example 3: Performance Determination of Composite Seed Coating Agent

[0054] In this test example, the film-forming property, pH value, compatibility, coating film-forming time and coating qualified rate of the composite seed coating agent (1.5% CS + MT150 μmol / L) obtained above were measured.

[0055] Among them, the film-forming property is determined by casting the composite seed coating agent on a 2×10cm glass plate to form a film with a film thickness of 0.08mm. The film-forming property is divided into three levels for examination. After uniform film formation, the glass plate is soaked in water for 0.5h, and the film can be completely scraped off the glass plate, which is level II; the film-forming agent cannot form a film on the glass plate, which is level III. The test results show that after the composite seed coating agent forms a film, it can be completely scraped off the glass plate, which is a level II film.

[0056] The pH value was measured using an acidometer. The pH of the compound seed coating agent was 6.5, which is close to neutral and meets the requirements for seed coating.

[0057] The compatibility test is to add different concentrations of melatonin (50, 100, 150, 200, 250 μmol / L) to chitosan solution (1.5%), observe whether there is reaction, precipitation, etc., and leave it for 1 day. No reaction, no precipitation, no stratification indicates good compatibility; slight reaction or a small amount of precipitation or a little stratification indicates general compatibility; severe reaction, precipitation, stratification indicates incompatibility and poor compatibility. The test results show that when different concentrations of melatonin are added to chitosan solution, stirred evenly, no reaction, precipitation, etc. occurs, and left for 1 day, the solution has no reaction, no precipitation, and no stratification, indicating good compatibility.

[0058] The coating film time test is to coat the seeds with the seed coating agent sample to be tested, and coat 100g of seeds with every 10mL solution. Stir with a glass rod, and after all the seeds are evenly coated with the seed coating agent, record the time required for the seed surface to solidify into a film, and for the seeds to not stick to each other or clump, and spread the seeds on clean germination paper and put them in an oven to dry. The test results show that it takes about 5 minutes for all the seeds to be evenly coated with the seed coating agent. Depending on the coating concentration, continue stirring for 5-10 minutes to solidify into a film on the seed surface, and the seeds will not stick to each other or clump.

[0059] The coating qualified rate is based on coating 100g of seeds with 10mL of solution. After the seeds are completely dried, 3 samples are randomly taken from the coated seeds, each with 100 seeds. Each seed is visually observed with a magnifying glass. Seeds with a surface coating covering area of ​​not less than 80% are qualified for coating. The number of qualified seeds is counted to calculate the coating qualified rate. The test results show that the coating qualified rate of the composite seed coating agent of the present invention reaches 95%.

[0060] It can be seen from this that the composite seed coating agent of the present invention uses chitosan and melatonin in combination, which can simultaneously meet the comprehensive requirements of film-forming property, pH, compatibility, coating film-forming time, and coating qualified rate.

[0061] Experimental Example 4: Effect of Seed Coating Agent on Corn Seed Germination under Salt Stress

[0062] 4.1 Effects of different concentrations of salt stress on corn seed germination

[0063] NaCl solutions with concentrations of 50, 100, 150, 200, and 250 mmol / L were prepared, and different gradient salt solutions were set to simulate the effect of salt stress environment on corn seed germination and screen the salt stress concentration.

[0064] Select corn seeds of uniform size and free of pests and diseases, disinfect with 1.0% sodium hypochlorite for 10 minutes, and rinse with distilled water 3-5 times. Two layers of filter paper were laid in the germination box, 10mL of distilled water was added to the control group, and 10mL of NaCl solution of different concentrations was added to the treatment group. 40 corn seeds were evenly placed in each germination box and placed in an artificial climate incubator (25°C, 16h light; 20°C, 8h dark, humidity of 65%-80%) for germination test. Three replicates were set for each treatment. The number of germinations was counted at a fixed time every day, and the germination potential, germination rate, germination index, vitality index, average germination time, etc. were calculated. The results are shown in Table 3.

[0065] Table 3 Effects of different concentrations of salt stress on corn seed germination

[0066]

[0067] As shown in Table 3, different concentrations of NaCl were used for salt stress, and 50 mmol / L was selected as the appropriate salt stress concentration for subsequent experiments.

[0068] 4.2 Effects of different concentrations of chitosan coating on corn seed germination under salt stress

[0069] Weigh 2.5, 5, 7.5 and 10 g of chitosan powder respectively, place them in 4 small beakers, numbered 1 to 4, add 0.6 wt% acetic acid solution, make the volume up to 100 mL, and stir continuously with a glass rod to accelerate dissolution, prepare chitosan solutions with concentrations of 2.5%, 5%, 7.5% and 10% for later use.

[0070] The seed coating method was the same as in Experiment 1, with distilled water as the control group 1 (CK), the salt stress condition without seed coating agent as the control group 2 (S), and chitosan-coated seeds of different concentrations as the treatment group. According to the salt stress concentration screened in Section 4.1, corn seeds were placed in a salt stress environment for germination test. Three replicates were set for each treatment. The test results are shown in Table 4.

[0071] Table 4 Effects of different concentrations of chitosan coating on corn seed germination under salt stress

[0072] deal with Germination rate / % Germination potential / % Germination days / d Germination Index Seedling length / cm Vitality Index CK <![CDATA[82±1.16 a ]]> <![CDATA[43±4.04 a ]]> <![CDATA[3.31±0.19 c ]]> <![CDATA[9.56±0.54 a ]]> <![CDATA[3.40±0.10 a ]]> <![CDATA[32.45±0.97 a ]]> S <![CDATA[62±3.46 d ]]> <![CDATA[24±1.73 b ]]> <![CDATA[3.66±0.09 ab ]]> <![CDATA[6.51±0.33 c ]]> <![CDATA[2.30±0.17 d ]]> <![CDATA[14.97±1.33 d ]]> S+2.5％ <![CDATA[65±7.02 cd ]]> <![CDATA[25±3.00 b ]]> <![CDATA[3.62±0.06 b ]]> <![CDATA[6.92±0.62 c ]]> <![CDATA[2.47±0.12 cd ]]> <![CDATA[17.06±1.68 cd ]]> S+5.0％ <![CDATA[77±1.73 ab ]]> <![CDATA[33±2.52 b ]]> <![CDATA[3.47±0.06 bc ]]> <![CDATA[8.45±0.20 b ]]> <![CDATA[2.90±0.10 b ]]> <![CDATA[24.50±0.98 b ]]> S+7.5％ <![CDATA[73±1.73 bc ]]> <![CDATA[28±8.08 b ]]> <![CDATA[3.87±0.18 a ]]> <![CDATA[7.24±0.14 c ]]> <![CDATA[2.83±0.15 b ]]> <![CDATA[20.54±1.49 c ]]> S+10.0％ <![CDATA[63±8.72 d ]]> <![CDATA[29±6.35 b ]]> <![CDATA[3.62±0.10 b ]]> <![CDATA[6.51±1.03 c ]]> <![CDATA[2.73±0.23 bc ]]> <![CDATA[17.87±3.84 cd ]]>

[0073] From the data in Table 4, it can be seen that under salt stress, different concentrations of chitosan coating have a significant promoting effect. Compared with the salt treatment group, the germination rate of the chitosan coating group increased by 1-15%. When the concentration was 5% and 7.5%, the improvement was more obvious, and the germination rate increased significantly by 15% and 11%, respectively, the seedling length increased by 26% and 23%, and the vitality index increased by 64% and 37%. Therefore, 5% was selected as the appropriate chitosan concentration for subsequent experiments.

[0074] 4.3 Effects of chitosan + different concentrations of melatonin on corn seed germination under salt stress

[0075] The treatment method was the same as that in Section 4.2, with distilled water as control group 1 (CK), salt stress conditions without seed coating as control group 2 (S), chitosan (5%) coated seeds as control group 3, and different concentrations of melatonin (50, 100, 150, 200, 250 μmol / L) combined with chitosan (5%) coating as treatment groups (when composite coating, the mixed volume ratio of melatonin solution and chitosan solution was 1:1). Three replicates were set for each treatment, and germination tests were carried out in a salt stress environment. The test results are shown in Table 5.

[0076] Table 5 Effects of 5% chitosan + different concentrations of melatonin (MT) on corn seed germination under salt stress

[0077] deal with Germination rate / % Germination potential / % Germination days / d Germination Index Seedling length / cm Vitality Index CK <![CDATA[85±6.43 a ]]> <![CDATA[42±2.52 a ]]> <![CDATA[2.83±0.06 b ]]> <![CDATA[12.87±1.10 a ]]> <![CDATA[3.97±0.18 a ]]> <![CDATA[50.96±2.54 a ]]> S <![CDATA[64±3.00 d ]]> <![CDATA[24±1.73 d ]]> <![CDATA[3.32±0.10 a ]]> <![CDATA[7.48±0.41 d ]]> <![CDATA[2.57±0.06 d ]]> <![CDATA[19.20±1.35 f ]]> 5% CS <![CDATA[73±5.00 bcd ]]> <![CDATA[30±2.52 bc ]]> <![CDATA[3.17±0.17 ab ]]> <![CDATA[10.05±0.76 c ]]> <![CDATA[2.91±0.11 c ]]> <![CDATA[29.26±3.29 de ]]> CS+MT50 <![CDATA[76±3.60 abc ]]> <![CDATA[33±4.04 b ]]> <![CDATA[3.12±0.12 ab ]]> <![CDATA[10.77±0.30 bc ]]> <![CDATA[2.97±0.10 c ]]> <![CDATA[31.94±0.44 cd ]]> CS+MT100 <![CDATA[79±4.04 ab ]]> <![CDATA[33±2.52 b ]]> <![CDATA[2.99±0.22 ab ]]> <![CDATA[11.65±0.63 b ]]> <![CDATA[3.16±0.04 b ]]> <![CDATA[36.78±1.54 b ]]> CS+MT150 <![CDATA[77±5.77 abc ]]> <![CDATA[27±2.89 cd ]]> <![CDATA[3.25±0.20 a ]]> <![CDATA[10.68±0.32 bc ]]> <![CDATA[3.02±0.08 bc ]]> <![CDATA[32.24±1.75 cd ]]> CS+MT200 <![CDATA[75±7.51 bc ]]> <![CDATA[28±4.62 bcd ]]> <![CDATA[2.91±0.31 b ]]> <![CDATA[11.40±0.86 b ]]> <![CDATA[02.91±0.10 c ]]> <![CDATA[33.08±1.53 c ]]> CS+MT250 <![CDATA[69±4.04 cd ]]> <![CDATA[30±2.52 bc ]]> <![CDATA[3.09±0.11 ab ]]> <![CDATA[9.83±0.39 c ]]> <![CDATA[2.89±0.04 c ]]> <![CDATA[28.38±1.47 e ]]>

[0078] From the results in Table 5, it can be seen that compared with the 5% chitosan coating group, the germination rate increased when the melatonin concentration was 50-200 μmol / L, and when it reached 250 μmol / L, the germination rate showed a downward trend. Among them, when the test group was CS+MT100 (5% chitosan + 100 μmol / L melatonin), the germination rate, germination potential, germination index, seedling length and vitality index were significantly increased by 6%, 3%, 16%, 9% and 26% compared with the single chitosan group. Therefore, under salt stress, when the chitosan concentration is 5% and the melatonin concentration is 100 μmol / L, it has the best promoting effect on corn seed germination.

[0079] In summary, suitable coating concentration can optimize the microenvironment around the seeds, promote the absorption of water and nutrients, and thus improve the germination rate of seeds. Too high or too low a concentration of the coating agent may have an adverse effect on the germination and growth of corn seeds. Therefore, it is crucial to select suitable coating materials and concentrations to achieve the coating effect of corn seeds. The seed coating agent provided by the present invention uses chitosan and melatonin in combination, and the two can play an effective synergistic role, which not only improves the quality and growth potential of corn seeds, but also has important significance for environmental protection and sustainable agricultural development. In particular, the present invention uses chitosan and melatonin for joint coating, which can effectively enhance the adaptability of corn seeds under normal conditions, adverse conditions, especially salt stress conditions, significantly improve the germination rate of corn seeds, and then promote the growth of seedlings and the increase of crop yield. Therefore, the present invention can provide a technical theoretical basis for the development of corn-specific seed coating agents and the improvement of film-forming properties, promote seed germination, reduce pollution, and increase crop yield, and has broad application prospects in the field of corn seed coating.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A seed coating agent for corn seed coating, characterized in that: The invention is composed of raw materials with the following concentrations: 0.75wt%-2.5wt% of chitosan, 50-75μmol / L of melatonin, and 0.2wt%-0.4wt% of acetic acid.

2. The seed coating agent for corn seed coating according to claim 1, characterized in that: When the seed coating agent is used for coating corn seeds under normal conditions, the concentration of chitosan is 0.75 wt %, and the concentration of melatonin is 75 μmol / L.

3. The seed coating agent for corn seed coating according to claim 1, characterized in that: When the seed coating agent is used for coating corn seeds under salt stress conditions, the concentration of chitosan is 2.5wt%, and the concentration of melatonin is 50μmol / L.

4. The method for preparing a seed coating agent for corn seed coating according to claim 1, characterized in that: The following steps are involved: The chitosan is mixed in the acetic acid solution to obtain a chitosan solution; melatonin is mixed in water to obtain a melatonin solution; the chitosan solution and the melatonin solution are mixed evenly to obtain the seed coating agent.

5. The method for preparing a seed coating agent for corn seed coating according to claim 4, characterized in that: The concentration of the chitosan solution is 1.5wt% to 5wt%; the concentration of the melatonin solution is 100 to 150 μmol / L.

6. The method for preparing a seed coating agent for corn seed coating according to claim 4, characterized in that: The concentration of the acetic acid solution is 0.4 wt % to 0.8 wt %.

7. The method for preparing a seed coating agent for corn seed coating according to claim 4, characterized in that: The mixing volume ratio of the chitosan solution to the melatonin solution is 1:

1.

8. The method for preparing a seed coating agent for corn seed coating according to claim 5, characterized in that: The concentration of the chitosan solution is 1.5 wt %; the concentration of the melatonin solution is 150 μmol / L.

9. The method for preparing a seed coating agent for corn seed coating according to claim 5, characterized in that: The concentration of the chitosan solution is 5wt%; the concentration of the melatonin solution is 100 μmol / L.

10. The use of the seed coating agent for corn seed coating according to any one of claims 1 to 3, characterized in that: The application is to coat corn seeds with the seed coating agent to enhance the germination of corn seeds under normal conditions or salt stress.

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