Bactericide composition for preventing and treating wheat scab

Abstract

The invention belongs to the technical field of bactericides, and particularly relates to a bactericide composition for preventing and treating wheat scab. The invention relates to a bactericide composition. The effective components of the bactericide composition are prepared by mixing L-carvone and prochloraz according to a mass ratio of 4: 6. After the L-carvone and the prochloraz are mixed, the L-carvone and the prochloraz have a synergistic effect on fusarium graminearum and have relatively high toxicity on the fusarium graminearum, and an important theoretical basis can be provided for developing and utilizing the volatile oil L-carvone to a greater extent and improving the activity of the plant volatile oil L-carvone on the fusarium graminearum.

Description

Technical Field

[0001] The present invention belongs to the technical field of fungicides, and particularly relates to a fungicide composition for controlling wheat scab. Background Art

[0002] Wheat scab is an important epidemic disease in wheat production, and its occurrence condition is that the wheat heading and flowering stage encounters continuous high temperature and high humidity weather. Due to different epidemic and damage degrees of the disease, it can cause a 50% reduction in production, and even a complete crop failure in severe cases. Wheat scab not only causes a reduction in wheat production, but also affects the quality of wheat. Toxins such as deoxynivalenol (DON) produced by the infection of Fusarium graminearum can cause varying degrees of poisoning in humans and livestock, threatening food security. At present, the prevention and control of wheat scab mainly rely on chemical fungicides. However, due to the increasing epidemic frequency of the disease and the increasing number of pesticide applications, the emergence of resistant strains in the field has become common. Since the first discovery of a carbendazim-resistant strain of Fusarium graminearum in 1922, resistant strains of Fusarium graminearum to commonly used control agents such as carbendazim have been successively reported in regions such as Jiangsu, Anhui, Zhejiang, and Henan in China, and their population numbers show a rapid growth trend, resulting in a significant decline in the field control effect, or even loss. Therefore, it has become an urgent task to develop new prevention and control strategies to address the resistance problem. The compounding of plant-derived active substances with different structural types and action mechanisms with chemical fungicides can achieve the reduction and efficiency increase of chemical pesticides, and delay the occurrence and development of pathogen resistance.

[0003] L-Carvone, also known as levocarvone, is a monoterpene compound, usually a colorless or light yellow liquid. Spearmint oil extracted from plants of the Lamiaceae family contains up to 80% carvone. Regnier et al. found that L-carvone has better inhibitory effects on postharvest pathogenic fungi of avocado such as Colletotrichum gloeosporioides, Lasiodiplodia theobromae, and Alternaria sp. than several monomers such as D-limonene, S-carvone, and cineole, and volatile oil of Lippia scaberrima. Moreover, L-carvone not only has a broad bactericidal spectrum, but also has advantages such as being green, safe, and having a unique action mode. It is an ideal plant-derived fungicide and can be used to control plant pathogenic fungi.

[0004] The inventors determined the antibacterial effects of L-carvone, pyraclostrobin, prochloraz, and tebuconazole on Fusarium graminearum by the mycelial growth rate method, and in single-agent EC 50On the basis of the values, L-carvone was mixed with pyraclostrobin, prochloraz, and tebuconazole in different proportions, and the toxicity of the mixtures against Gibberella zeae was determined. The co-toxicity coefficient was calculated using the Sun Yunpei method to screen out the agent combinations with high antibacterial activity against Gibberella zeae, clarify the optimal ratio, provide a theoretical basis for the development and application of the mixture of L-carvone and chemical fungicides for controlling Gibberella zeae, and provide a new strategy for the green prevention and control of wheat scab. Summary of the Invention

[0005] The purpose of the present invention is to provide a fungicide composition for controlling wheat scab, which provides a theoretical basis for delaying the development of drug resistance of Gibberella zeae and the development and application of the mixture of volatile oil and fungicide.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A fungicide composition, wherein the active ingredient of the fungicide composition is composed of L-carvone and prochloraz mixed in a mass ratio of 4:6.

[0008] The present invention also provides the application of the described fungicide composition in controlling wheat scab.

[0009] Specifically, the wheat scab is caused by infection with Fusarium graminearum.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The mixture of L-carvone and prochloraz in the present invention shows a synergistic effect against Gibberella zeae and has relatively high toxicity to Gibberella zeae, which can provide an important theoretical basis for the further development and utilization of L-carvone and improving the activity of L-carvone against Gibberella zeae. Detailed Embodiments

[0012] The technical solutions of the present invention patent are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art without creative work based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0013] 1. Test Materials

[0014] 1.1 Test reagents and culture media

[0015] Main reagents: 99% L-carvone and 98% prochloraz technical (Shanghai Aladdin Biochemical Technology Co., Ltd.); 97% tebuconazole and 99% pyraclostrobin technical (Qingdao Hailir Pesticide & Chemical Industry Group).

[0016] Potato Dextrose Agar (PDA) medium: 1000 mL of water, 200 g of potato, 18 g of agar, 20 g of glucose.

[0017] 1.2 Phytopathogenic fungi

[0018] The test strain was Fusarium graminearum, provided by the Plant Protection Pathology Laboratory of the College of Agriculture, Xinyang Agriculture and Forestry University, Henan Province.

[0019] 2. Test methods

[0020] 2.1 Determination of the antibacterial activities of L-carvone, pyraclostrobin, prochloraz, and tebuconazole against Fusarium graminearum

[0021] The mycelial growth rate method was used to determine the antibacterial activities of L-carvone, pyraclostrobin, prochloraz, and tebuconazole against Fusarium graminearum. The original drugs were formulated into a stock solution of 9000 μg / mL with acetone and 0.1% Tween-80. According to the pre-test results, the concentration design was carried out. The stock solution was serially diluted with sterile water. 1 mL of different concentration dilutions was pipetted into 44 mL of PDA medium respectively, shaken well and then poured into 3 Petri dishes (90 cm), 15 mL per dish, to prepare the medicated medium. A mycelial disc of Fusarium graminearum cultured for 3 days with a puncher with an inner diameter of 5 mm was placed in the center of the plate and cultured in the dark in an incubator at 25 ± 1 °C. Each treatment was repeated 3 times. After 72 h, the colony diameter of each treatment was measured by the cross method.

[0022] Mycelial growth inhibition rate = [(average colony growth diameter of the control group - 0.5) - (average colony growth diameter of the treatment group - 0.5)] / (colony growth diameter of the control group - 0.5) × 100%

[0023] 2.2 Combined effects of L-carvone mixed with different fungicides

[0024] On the basis of the single-agent bioactivity determination, L-carvone was mixed with 3 fungicides at mass ratios of active ingredients of 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, and 1:9 to prepare the medicated PDA medium; without adding the agent as the control, each treatment was repeated 3 times, and the inhibition rate of the mixed agents against the growth of Fusarium graminearum was determined according to the method of 2.1.

[0025] The toxicity regression equations and EC of each mixed agent and single agent were calculated using SPSS 22.0 50, according to Sun Yunpei's method, calculate the single-agent toxicity index (TI), the toxicity index of the mixture (ATI), the theoretical toxicity index of the mixture (TTI), and the co-toxicity coefficient (CTC) to determine whether the mixture has a synergistic effect. The calculation formulas and standards are as follows:

[0026] Toxicity index TI = Standard agent (EC 50 ) / Test agent (EC 50 ) × 100

[0027] Measured toxicity index of the mixture ATI = Standard agent (EC 50 ) / Mixture (EC 50 ) × 100

[0028] TTI = Toxicity index of A × Content of A in the mixture (%) + Toxicity index of B × Content of B in the mixture (%)

[0029] Co-toxicity coefficient (CTC) = Measured toxicity index of the mixture ATI / Theoretical toxicity index of the mixture TTI × 100

[0030] CTC ≤ 80 indicates antagonistic effect; 80 < CTC < 120 indicates additive effect; CTC ≥ 120 indicates synergistic effect

[0031] 3. Results and Analysis

[0032] 3.1 Toxicity determination of L-carvone, pyraclostrobin, prochloraz, and tebuconazole against Gibberella zeae

[0033] The antibacterial effects of L-carvone, pyraclostrobin, prochloraz, and tebuconazole against Gibberella zeae were determined by the mycelial growth rate method. The results are shown in Table 1.

[0034] Table 1 Toxicity determination of test agents against Gibberella zeae

[0035]

[0036] As can be seen from Table 1, the four fungicides tested all had varying degrees of inhibitory effects on Gibberella zeae. Tebuconazole had the best antibacterial effect, with an EC 50 of 0.485 mg / L; prochloraz had a relatively good antibacterial effect, with an EC 50 of 0.811 mg / L; the plant-derived fungicide L-carvone had an obvious antibacterial effect, with an EC 50 of 22.281 mg / L.

[0037] 2.2 Toxicity determination of the mixture of L-carvone and different fungicides

[0038] 2.2.1 Toxicity determination results of the mixture of L-carvone and pyraclostrobin

[0039] The results are shown in Table 2.

[0040] Table 2 Joint action of carvone (A) and pyraclostrobin (B) mixtures on Gibberella zeae

[0041] Mixture ratio (A: B) <![CDATA[EC 50 (mg / L)]]> ATI TTI CTC Evaluation 10：0 22.281 100.000 -- -- -- 0：10 1.838 1212.242 -- -- -- 1：9 3.489 638.607 1101.017 58.002 Antagonism 2：8 3.702 601.864 989.793 60.807 Antagonism 3：7 2.516 885.572 878.569 100.797 Additive 4：6 2.453 908.316 767.345 118.371 Additive 5：5 2.812 792.354 656.121 120.763 Synergistic 6：4 3.748 594.477 544.897 109.099 Additive 7：3 5.020 443.845 433.672 102.346 Additive 8：2 3.987 558.841 322.448 173.312 Synergistic 9：1 4.109 542.249 211.224 256.717 Synergistic

[0042] As can be seen from Table 2, the median effective concentration EC 50 of the mixtures of carvone and pyraclostrobin at different ratios against Gibberella zeae was between 2.453 - 5.020 mg / L; different ratios showed different effects. The co-toxicity coefficient CTC of the 1:9 and 2:8 ratios was less than 80, showing an antagonistic effect; the co-toxicity coefficient CTC of the 5:5, 8:2, and 9:1 ratios was greater than 120, showing a synergistic effect; the co-toxicity coefficient CTC of the other 4 mixture ratios was between 80 - 120, showing an additive effect. Among them, the 9:1 ratio had the most obvious synergistic effect, and the co-toxicity coefficient CTC was as high as 256.717. It can be seen that mixing carvone and pyraclostrobin in a reasonable ratio can better inhibit the growth of Gibberella zeae, and the best mass ratio of the effective components for their mixture is 9:1.

[0043] 2.2.2 Toxicity determination results of the mixture of carvone and prochloraz

[0044] The results are shown in Table 3.

[0045] Table 3 Joint action of carvone (A) and prochloraz (C) mixtures on Gibberella zeae

[0046]

[0047]

[0048] As can be seen from Table 3, the median effective concentration EC 50 of the mixtures of carvone and prochloraz at different ratios against Gibberella zeae was between 0.434 - 4.437 mg / L. Among them, the EC 50 of the 4:6 ratio was 0.892 mg / L (close to 0.875 mg / L of prochloraz), and the amount of prochloraz used was reduced by 38.9%, with an obvious synergistic effect, and the co-toxicity coefficient CTC value was 304.066. The EC 50 of the 5:5 ratio was 0.537 mg / L, and the amount of prochloraz used was reduced by 50%, still maintaining a high antibacterial effect, and the co-toxicity coefficient CTC was 291.440. The other ratios also all showed synergistic or additive effects. It can be seen that mixing carvone and prochloraz in different ratios can better inhibit the growth of Gibberella zeae. Mixing the two can effectively reduce the dosage of chemical fungicides, reduce the risk of chemical residues, and delay the generation of drug resistance.

[0049] 2.2.3 Toxicity determination results of the mixture of L-carvone and tebuconazole

[0050] The results are shown in Table 4.

[0051] Table 4 Joint action of the mixture of L-carvone (A) and tebuconazole (D) against Gibberella zeae

[0052]

[0053]

[0054] As can be seen from Table 4, the median effective concentration EC 50 of the mixtures of different ratios of L-carvone and tebuconazole against Gibberella zeae ranged from 0.562 to 5.008 mg / L. The co-toxicity coefficient CTC showed that the CTC values of the ratios of 1:9, 3:7, 4:6, and 8:2 were all less than 80, showing antagonistic effects; while the CTC values of the ratios of 2:8, 5:5, 6:4, 7:3, and 9:1 were between 80 and 120, showing additive effects. However, the EC 50 of each mixture was higher than that of tebuconazole alone. It can be seen that the mixture of L-carvone and tebuconazole not only did not show synergistic effects, but instead had weaker overall toxicity than tebuconazole alone due to antagonistic or additive effects. Therefore, the mixture of the two is not recommended for controlling Gibberella zeae of wheat.

[0055] In summary, although the mixture of L-carvone and pyraclostrobin showed synergistic effects at some ratios, the overall effect was not as good as that of the mixture with prochloraz. The mixture of L-carvone and tebuconazole mostly showed antagonistic or additive effects, and the overall toxicity was weaker than that of tebuconazole alone. Therefore, the mixture of the two is not recommended for controlling Gibberella zeae of wheat. The mixture of L-carvone and prochloraz shows extremely broad application prospects. This combination can not only effectively improve the inhibitory effect on Gibberella zeae of wheat, but also significantly reduce the usage amount of chemical fungicides, meeting the requirements of green control and sustainable agricultural development. This discovery provides new ideas and theoretical basis for the green control of Gibberella zeae of wheat, and also provides important scientific reference for the development of new mixed fungicides.

Claims

1. A fungicide composition, characterized in that: The active ingredient of the fungicide composition is prepared by mixing L-carvone and prochloraz in a mass ratio of 4:

6.

2. Use of the fungicide composition according to claim 1 in preventing and treating wheat fusarium head blight.

3. The use according to claim 2, characterized in that: The wheat fusarium rust is caused by infection of Fusarium graminearum.

Images