Application of bactericide in prevention and treatment of pepper southern blight and method for preventing and treating pepper southern blight

Abstract

The invention belongs to the technical field of crop disease and pest control, and particularly relates to application of a bactericide in controlling pepper southern blight and a method for controlling pepper southern blight. The invention provides application of a bactericide in prevention and treatment of pepper southern blight. The bactericide comprises hexaconazole and / or azoxystrobin. The varieties of the peppers comprise disease-resistant varieties and disease-susceptible varieties; the use concentration of the hexaconazole is 20 to 100 [mu] g / mL; the use concentration of the azoxystrobin is 20 to 100 [mu] g / mL. It is found that hexaconazole and azoxystrobin have a good comprehensive control effect on resistant and susceptible varieties, disease management can be conducted in a mode that the resistant varieties and the bactericide are combined when southern blight is controlled, the incidence degree of the southern blight can be effectively reduced, the usage amount of the bactericide is reduced, and stable growth of plants is maintained; the root morphology and antioxidant enzyme regulation of the disease-resistant variety are superior to those of the susceptible variety, and the protection activity control effect of the disease-resistant variety is obviously higher than that of the susceptible variety.

Description

Technical Field

[0001] The invention belongs to the technical field of crop disease and insect pest control, and particularly relates to application of a fungicide in controlling pepper white rot and a method for controlling pepper white rot. Background Art

[0002] Pepper, a member of the genus Capsicum, is an annual or limited perennial herb. The fruit is usually conical or oblong, green when immature, and bright red, green or purple when ripe, with red being the most common. Pepper fruit has a spicy taste due to the capsaicin contained in the peel, which can increase appetite. The vitamin C content in pepper ranks first among vegetables.

[0003] As a soil-borne disease with serious damage caused by the infection of Sclerotium rolfsii Sacc., pepper white rot is the primary organ that comes into direct contact with the fungus, and is also the first and most direct site of damage. In recent years, with the continuous expansion of pepper production, the incidence and area of ​​infection caused by its infection have also increased year by year, and it has now become one of the main field diseases affecting the normal production of pepper. There are many methods to prevent and control white rot, mainly including the following: chemical control, field agricultural measures management, biological control, planting resistant varieties, etc. At present, relying on chemical agents is still the main measure for field control of pepper white rot, but China currently has no registered pesticides for the prevention and control of white rot on peppers, nor has it screened and publicly promoted resistant pepper varieties. Therefore, it is particularly important to find fungicides for the prevention and control of white rot. Summary of the invention

[0004] The purpose of the present invention is to provide an application of a fungicide in preventing and controlling pepper white rot and a method for preventing and controlling pepper white rot, so as to effectively prevent and control pepper white rot.

[0005] In order to achieve the above object, the present invention provides the use of a fungicide in preventing and controlling pepper white rot, wherein the fungicide comprises hexaconazole and / or azoxystrobin;

[0006] The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8;

[0007] The use concentration of hexaconazole is 20 to 100 μg / mL;

[0008] The use concentration of the azoxystrobin is 20-100 μg / mL.

[0009] Preferably, the disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435;

[0010] The susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101.

[0011] Preferably, the fungicide inhibits the growth of pepper white rot pathogen and prevents pepper white rot.

[0012] Preferably, the dosage form of the hexaconazole is 95wt.% powder; the dosage form of the azoxystrobin is 98wt.% powder.

[0013] The present invention also provides a method for preventing pepper white rot, wherein a fungicide is applied to pepper when pepper seedlings are transplanted to the field;

[0014] The bactericide comprises hexaconazole and / or azoxystrobin;

[0015] The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8;

[0016] The use concentration of hexaconazole is 20-100 μg / mL, and the application amount is 5 mL / plant;

[0017] The use concentration of the azoxystrobin is 20-100 μg / mL, and the application amount is 5 mL / plant.

[0018] Preferably, the fungicide is applied by root irrigation.

[0019] Preferably, the disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435;

[0020] The susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101.

[0021] The present invention also provides a method for treating pepper white rot, wherein a fungicide is applied to pepper 24 hours after the pepper is infected with pepper white rot pathogen;

[0022] The bactericide comprises hexaconazole and / or azoxystrobin;

[0023] The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8;

[0024] The use concentration of hexaconazole is 20-100 μg / mL, and the application amount is 5 mL / plant;

[0025] The use concentration of the azoxystrobin is 20-100 μg / mL, and the application amount is 5 mL / plant.

[0026] Preferably, the fungicide is applied by root irrigation.

[0027] Preferably, the disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435;

[0028] The susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101.

[0029] Beneficial effects:

[0030] The present invention provides an application of a fungicide in preventing and controlling pepper white rot, wherein the fungicide comprises hexaconazole and / or azoxystrobin; the pepper varieties comprise disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8; the use concentration of the hexaconazole is 20 to 100 μg / mL; the use concentration of azoxystrobin is 20 to 100 μg / mL. The present invention conducts an in vitro activity test on pepper white rot, and determines the indoor toxicity of different fungicides to pepper white rot, and the results show that hexaconazole and azoxystrobin have good comprehensive control effects on resistant and susceptible varieties. Potted plant protection efficacy tests showed that 20-100 μg / mL of hexaconazole and / or myclobutanil had good comprehensive protection efficacy. When preventing and controlling white rot, resistant varieties and fungicides can be used in combination for disease management, which can effectively reduce the incidence of white rot, reduce the amount of fungicides used, and maintain stable plant growth. In addition, the root morphology and antioxidant enzyme regulation of resistant varieties were better than those of susceptible varieties, and the protective activity control effect of resistant varieties was significantly higher than that of susceptible varieties. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0032] Figure 1 Cluster diagram for disease resistance analysis of different pepper varieties based on DI values;

[0033] Figure 2 This is a comparison chart of disease index of different pepper varieties;

[0034] Figure 3 This is a comparison chart of the growth potential differences of different pepper varieties 4 days after inoculation;

[0035] Figure 4 The results of the potted plant protection test of fungicides against pepper white rot; P represents protective activity (preventive effect); C represents therapeutic activity (therapeutic effect);

[0036] Figure 5The figure is a comparison of disease index and control effect of different pepper varieties; a is a disease-resistant variety, b is a disease-susceptible variety; different lowercase letters indicate significant differences between treatments under the same variety (P < 0.05), and different uppercase letters indicate significant differences between varieties under the same treatment (P < 0.05);

[0037] Figure 6 This is a comparison of the growth differences between different pepper varieties after 5 days of inoculation; c is a disease-resistant variety, and d is a disease-susceptible variety;

[0038] Figure 7 This is a comparison chart of the root morphology (total root length, root projection area, root volume) of different pepper varieties inoculated with fungi for 5 days between different treatments; a is a disease-resistant variety, b is a disease-susceptible variety; different lowercase letters indicate significant differences between treatments under the same variety (P < 0.05);

[0039] Figure 8 The following is a comparison of root morphology phenotypes of different pepper varieties inoculated with fungi for 5 days under different treatments; c is a disease-resistant variety, and d is a disease-susceptible variety;

[0040] Fig. 9 The effect of fungicide application on root antioxidant enzyme activity after S. rolf-origin infection of disease-resistant varieties; different lowercase letters indicate significant differences among treatments for the same variety (P < 0.05);

[0041] Fig.10 The effect of fungicide application on root antioxidant enzyme activity after S. rot infection of susceptible varieties; different lowercase letters indicate significant differences among treatments for the same variety (P<0.05);

[0042] in, Figures 5 to 10 In the table, P represents protective activity (preventive effect); C represents therapeutic activity (therapeutic effect); A represents hexaconazole, B represents azoxystrobin, 1 represents a concentration of 50 μg / mL, and 2 represents a concentration of 100 μg / mL;

[0043] Fig.11 This is the result of correlation analysis between different indicators of resistant and susceptible varieties. DETAILED DESCRIPTION

[0044] The present invention provides the use of a fungicide in preventing and controlling white rot of pepper, wherein the fungicide comprises hexaconazole and / or azoxystrobin;

[0045] The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8;

[0046] The use concentration of hexaconazole is 20 to 100 μg / mL;

[0047] The use concentration of the azoxystrobin is 20-100 μg / mL.

[0048] In the present invention, as an embodiment, the disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435; as another embodiment, the disease-resistant variety is Qianjiao No. 8. As an embodiment, the susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101; as another embodiment, the susceptible variety is Layan 101. The present invention uses the squared Euclidean distance method to perform cluster analysis, and divides pepper varieties into two types: susceptible and resistant. It is found that the root morphology and antioxidant enzyme regulation of the disease-resistant varieties are better than those of the susceptible varieties, so that the protective activity control effect of the disease-resistant varieties is significantly higher than that of the susceptible varieties. As an embodiment, the disease index of the disease-resistant variety to white rot is ≤20.

[0049] In the present invention, the fungicide inhibits the growth of pepper white rot pathogen and prevents pepper white rot. As an embodiment, the pepper white rot pathogen is Sclerotium rolfsii Sacc.

[0050] In the present invention, as an embodiment, the use concentration of hexaconazole is 20-100μg / mL; as another embodiment, the use concentration of hexaconazole is 50μg / mL. As an embodiment, the dosage form of hexaconazole is 95wt.% powder. As an embodiment, the use method of hexaconazole is root irrigation. As an embodiment, the use concentration of azoxystrobin is 20-100μg / mL; as another embodiment, the use concentration of azoxystrobin is 50μg / mL. As an embodiment, the dosage form of azoxystrobin is 98wt.% powder. As an embodiment, the use method of azoxystrobin is root irrigation. Indoor toxicity assays found that hexaconazole had the best antibacterial effect, EC 50 The value was 0.00139 μg / mL, and the inhibitory effects of carboxin, diniconazole, and fluazinam were second. 50 The values ​​were all 0.1 μg / ml; the inhibitory effects were followed by pyraclostrobin, picoxystrobin, azoxystrobin and tebuconazole, EC 50 The values ​​were 0.2, 0.3, 0.4, and 0.7 μg / mL, respectively. Difenoconazole had the worst inhibitory effect, with EC 50The value is 3.3 μg / mL; based on the different activity mechanisms and activity sizes of fungicides against pathogens, azoxystrobin, carboxin, fluazinam, picoxystrobin, and hexaconazole were selected for potted plant control experiments for efficacy determination, and it was found that hexaconazole and azoxystrobin had good comprehensive control effects on resistant and susceptible varieties. The present invention screened hexaconazole and azoxystrobin as fungicides with good comprehensive efficacy through potted plant efficacy determination, and the resistant varieties and fungicides combined mode can be used for disease management when preventing and controlling white rot, which can effectively reduce the incidence of white rot, reduce the amount of fungicides used, and maintain stable plant growth.

[0051] The present invention also provides a method for preventing pepper white rot, wherein a fungicide is applied to pepper when pepper seedlings are transplanted to the field;

[0052] The bactericide comprises hexaconazole and / or azoxystrobin;

[0053] The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8;

[0054] The use concentration of hexaconazole is 20-100 μg / mL, and the application amount is 5 mL / plant;

[0055] The use concentration of the azoxystrobin is 20-100 μg / mL, and the application amount is 5 mL / plant.

[0056] In the present invention, as an embodiment, the method of applying the fungicide includes root irrigation.

[0057] In the present invention, as an embodiment, the use concentration of hexaconazole is 20-100 μg / mL; as another embodiment, the use concentration of hexaconazole is 50 μg / mL. As an embodiment, the dosage form of hexaconazole is 95wt.% powder. As an embodiment, the application amount of hexaconazole is 5mL / plant; as another embodiment, the application amount of hexaconazole is 5mL / plant.

[0058] In the present invention, as an embodiment, the concentration of azoxystrobin is 20-100 μg / mL; as another embodiment, the concentration of azoxystrobin is 50 μg / mL. As an embodiment, the dosage form of azoxystrobin is 98wt.% powder. As an embodiment, the amount of azoxystrobin applied is 5 mL / plant; as another embodiment, the amount of hexaconazole applied is 5 mL / plant.

[0059] In the present invention, as an embodiment, the disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435; as another embodiment, the disease-resistant variety is Qianjiao No. 8. As an embodiment, the susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101; as another embodiment, the susceptible variety is Layan 101. The present invention limits pepper varieties so that disease management can be carried out in a combined mode with fungicides, which can effectively reduce the incidence of the disease white rot, reduce the amount of fungicides used, and maintain stable plant growth.

[0060] The present invention also provides a method for treating pepper white rot, wherein a fungicide is applied to pepper 24 hours after the pepper is infected with pepper white rot pathogen;

[0061] The bactericide comprises hexaconazole and / or azoxystrobin;

[0062] The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8;

[0063] The use concentration of hexaconazole is 20-100 μg / mL, and the application amount is 5 mL / plant;

[0064] The use concentration of the azoxystrobin is 20-100 μg / mL, and the application amount is 5 mL / plant.

[0065] In the present invention, as an embodiment, the method of applying the fungicide includes root irrigation.

[0066] In the present invention, as an embodiment, the use concentration of hexaconazole is 20-100 μg / mL; as another embodiment, the use concentration of hexaconazole is 50 μg / mL. As an embodiment, the dosage form of hexaconazole is 95wt.% powder. As an embodiment, the application amount of hexaconazole is 5mL / plant; as another embodiment, the application amount of hexaconazole is 5mL / plant.

[0067] In the present invention, as an embodiment, the concentration of azoxystrobin is 20-100 μg / mL; as another embodiment, the concentration of azoxystrobin is 50 μg / mL. As an embodiment, the dosage form of azoxystrobin is 98wt.% powder. As an embodiment, the amount of azoxystrobin applied is 5 mL / plant; as another embodiment, the amount of hexaconazole applied is 5 mL / plant.

[0068] In the present invention, as an embodiment, the disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435; as another embodiment, the disease-resistant variety is Qianjiao No. 8. As an embodiment, the susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101; as another embodiment, the susceptible variety is Layan 101. The present invention limits pepper varieties so that disease management can be carried out in a combined mode with fungicides, which can effectively reduce the incidence of the disease white rot, reduce the amount of fungicides used, and maintain stable plant growth.

[0069] The results of the examples of the present invention show that whether it is hexaconazole or azoxystrobin, the preventive effect on disease-resistant varieties is better at 20-100 μg / mL, and the best effect is at 50 μg / mL and 100 μg / mL. When hexaconazole is 50 μg / mL, the therapeutic effect on susceptible varieties is better than that on resistant varieties. When the concentration rises to 100 μg / mL, the therapeutic effect of resistant varieties is significantly increased, but the control effect of susceptible varieties is not significantly improved. At 50 μg / mL and 100 μg / mL of azoxystrobin, the control effect of susceptible varieties is significantly higher than that of resistant varieties.

[0070] To further illustrate the present invention, the application of the fungicide provided by the present invention in preventing and controlling pepper white rot and a method for preventing and controlling pepper white rot are described in detail below in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0071] All data in the examples of the present invention are the average values ​​of at least three independent replicates, and variance analysis was performed using SPSS 26.0 statistical software for data processing and analysis, and P ≤ 0.05 was considered to be significantly different.

[0072] Example 1

[0073] 1. Materials and Methods

[0074] 1.1 Test materials and instruments

[0075] (1) Sclerotium rolfsii Sacc.: Culture on PDA plates in a constant temperature incubator at 25±1°C and store at 4°C.

[0076] (2) Pepper varieties: Yanjiao 485 (number P1) and Yanjiao 435 (number P2), produced by Chongqing Keguang Seedling Co., Ltd.; Xiangla No. 7 (number P3) and Xiangla No. 14 (number P4), produced by Hunan Xiangyan Seed Co., Ltd.; Qianjiao No. 8 (number P5), Zunla No. 9 (number P6), Layan No. 3 (number P7), Layan No. 12 (number P8), and Layan No. 101 (number P9), provided by the Pepper Research Institute of Guizhou Academy of Agricultural Sciences. All peppers were cultured in a greenhouse (temperature 25°C, photoperiod 16h / 8h day and night alternation, light intensity 700-1100Lux) until 6-8 true leaves were transplanted into pots for the next test. All experimental pepper seedlings had the same growth conditions and growth.

[0077] (3) Test fungicide technical powders: 98wt.% azoxystrobin technical powder (Macklin), 98wt.% carboxin technical powder (Macklin), 98wt.% propiconazole technical powder (Alfa), 95wt.% dimethoate technical powder (Source Leaf Biological), 98wt.% thiophanate-methyl technical powder (Source Leaf Biological), ≥98wt.% diniconazole technical powder (Source Leaf Biological), ≥98wt.% tebuconazole technical powder (Adamas-beta), ≥95wt.% cyproconazole technical powder (Macklin), 98wt.% fluazinam technical powder (Macklin), 98wt.% picoxystrobin technical powder (Macklin), 95wt.% hexaconazole technical powder (Source Leaf Biological), and ≥98wt.% benomyl technical powder (Source Leaf Biological).

[0078] (4) Instruments and equipment: clean bench, constant temperature incubator, root scanner, ELISA reader

[0079] 1.2 Test methods

[0080] 1.2.1 Identification of resistance of different pepper varieties to white rot

[0081] A pot experiment was used to detect the differences in resistance of different pepper varieties to white rot. The inoculation method of the pot experiment was based on Song et al. (Song D, Wen R, Chen K, et al. Application of thifluzamide to stem rot in peppers: Infection and control mechanisms of sclerotium rolfsii [J]. Pesticide Biochemistry and Physiology, 2024: 105846.), with each variety replicated 5 times and 10 peppers in each replicate.

[0082] (1) Observe the growth of peppers 4 days after inoculation and determine the disease index (DI). The determination and classification of the disease index (DI) are as follows: Measure the length of the shrunken stem base of the plant (assuming the length of the browning and shrunken stem base is X):

[0083] 0 = no browning at the stem base, and the whole plant is disease-free;

[0084] 1 = No browning at the stem base, but the plant is slightly wilted or the leaves are yellowing;

[0085] 3 = Browning and shrinkage of the stem base X≤1cm, slight wilt or yellowing of leaves;

[0086] 5 = Browning and shrinkage of stem base X≤1cm, leaves shrink / fall off;

[0087] 7 = Browning and shrinkage of stem base 1<X≤2cm, leaves shrink / fall off;

[0088] 9 = Browning and shrinkage of stem base 2<X≤3cm, leaves shrink / fall off;

[0089] 10 = The stem base turns brown and shrinks by 3 cm ≤ X, and the plant dies;

[0090] Disease index (DI) = [∑ (number of diseased plants at each level × corresponding level) / (total number of plants surveyed × highest level value)] × 100.

[0091] (2) Taking the DI value (disease index) of nine pepper varieties as an indicator, cluster analysis was performed using SPSS26.0 software and the squared Euclidean distance method;

[0092] The identification results showed that the nine pepper varieties could be divided into two different resistance types: P5, P2, and P1 (DI≤45.8) were resistant varieties; P3, P9, P6, P7, P4, and P8 (DI>45.8) were susceptible varieties ( Figure 1 ; The disease index showed an upward trend as the resistance weakened ( Figure 2 ), that is, different pepper varieties have different degrees of disease ( Figure 3 ), showing different resistance to white rot. Among them, the disease index of the resistant variety P5 (Qianjiao No. 8) was the smallest, at 37.60, and the disease index of the susceptible variety P9 (Layan 101) was the largest, reaching 74.00. The disease index of the resistant variety Qianjiao No. 8 was significantly lower than that of the susceptible variety Layan 101 (P<0.05).

[0093] 1.2.2 Screening of fungicides for controlling pepper white rot

[0094] 1.2.2.1 In vitro activity test of fungicides against pepper white rot

[0095] The mycelium growth rate method was used to test the in vitro activity of 12 fungicides against pepper bacterial rot.

[0096] (1) Before the test, the test strains were activated and put into use. On the culture dish full of mycelium, a 0.5 cm diameter punch was used to punch a bacterial cake at the edge of the mycelium. One bacterial cake was inoculated on each plate and inoculated in the center of the drug-containing / drug-free culture dish (preparation of drug-containing / drug-free culture dishes: weigh the test fungicide and dissolve it with 0.5 mL DMSO, then add 4.5 mL of an aqueous solution containing 0.2% Tween 20 to prepare a drug-containing mother solution, and use an aqueous solution prepared in the same manner without the fungicide as a blank control, i.e., the drug-free mother solution. Finally, add all the drug-containing / drug-free mother solutions into a conical flask containing PDA (45 mL) that has not yet cooled, shake it while hot and pour it into the culture dish. Pour 3 dishes into each conical flask. After solidification, the drug-containing / drug-free culture dishes are obtained).

[0097] (2) After inoculation, place the culture dish in a constant temperature incubator at 25°C and avoid light. When the blank control colony grows to a diameter of about 5.5 cm, measure the colony diameter of each culture dish using the cross method and calculate the antibacterial rate of each fungicide treatment. In each test, three concentration gradients are set for one fungicide, each concentration gradient is a treatment, and each treatment is repeated 3 times. The concentration of each fungicide is lowered in turn and adjusted according to the concentration results to continue screening until the half-maximum effective inhibition concentration (EC 50 ) until. Among them, the inhibition rate (%) = (control colony diameter - treatment colony diameter) / (control colony diameter - 0.5) × 100%; according to the logarithmic value of each fungicide concentration and the corresponding inhibition rate, the toxicity regression equation (y = a + bx), the effective inhibition concentration (EC 50 ) and correlation coefficient (R 2 ), and the results are shown in Table 1.

[0098] Table 1 Results of indoor toxicity test of fungicides against pepper white rot

[0099] Reagent name <![CDATA[EC 50 (μg / mL)]]> Regression equation <![CDATA[Correlation coefficient (R 2 )]]> Hexaconazole 0.00139±0.0i y=1.3812x+7.4738 0.9725 Carboxin 0.1±0.0h y=1.0708x+6.0417 0.9736 Diniconazole 0.1±0.0h y=2.0035x+6.6908 0.9639 Cyproconazole 0.1±0.0h y=1.2031x+6.0022 0.9667 Fluazifop 0.1±0.0h y=0.7853x+5.7324 0.8346 Bai Kemin 0.2±0.0g y=0.9397x+5.6250 0.8268 Picoxystrobin 0.3±0.1f y=0.3088x+5.1456 0.9657 Azoxystrobin 0.4±0.0e y=0.9100x+5.3650 0.9550 Tebuconazole 0.7±0.1d y=0.8514x+5.1402 0.9791 Propiconazole 1.7±0.1c y=1.4051x+4.6670 0.9556 Chlorothalonil 2.7±0.3b y=0.4506x+4.8069 0.8947 Difenoconazole 3.3±0.1a y=1.6543x+4.1384 0.9736

[0100] Note: Different lowercase letters indicate significant differences.

[0101] According to Table 1, the toxicity effects of different fungicides are quite different. Hexaconazole has the most significant inhibitory effect on the mycelium of S. rolfsii in the in vitro activity test. 50 The value was 0.00139μg / mL; the inhibitory effects of carboxin, diniconazole, fluazinam, and cyproconazole were second, and EC 50 The values ​​were all 0.1 μg / mL; the inhibitory effects were followed by pyraclostrobin, picoxystrobin, azoxystrobin and tebuconazole, with EC50 values ​​of 0.2, 0.3, 0.4 and 0.7 μg / mL, respectively; difenac had the worst inhibitory effect, with EC50 values ​​of 0. 50The value is 3.3μg / mL.

[0102] 1.2.2.2 Screening of fungicide efficacy against pepper varieties resistant to and susceptible to white rot in potted plants

[0103] The inoculation method is the same as step 1.2.2.1. The fungicide should be irrigated to the roots 24 hours before or 24 hours after inoculation, with an application rate of 5 mL per pepper plant.

[0104] According to the results of 1.2.1, two pepper varieties with the greatest difference in disease resistance (P5 and P9, respectively resistant and susceptible varieties) were selected; according to the results of the in vitro activity test in 1.2.2.1 and the mechanism of action of different fungicides, five fungicides (hexaconazole, carboxin, fluazinam, picoxystrobin, azoxystrobin) were planned for potted plant experiments, with the test concentration of 20 μg / mL, and the inoculated mycelium treated with clean water as the blank control. Each fungicide was a treatment, with 15 seedlings per treatment, 5 replicates, and the disease index was statistically calculated 5 days after inoculation and the relevant control effect was calculated. Among them, the evaluation of the disease index was the same as in 1.2.1, and the control effect was calculated based on the disease index, and the control effect (%) = [(blank group disease index - treatment group disease index) / blank group disease index] × 100%.

[0105] According to the statistical results, the five fungicides showed different control effects on resistant and susceptible pepper varieties at a fungicide concentration of 20 μg / mL, and there was a difference between the control effects of protective activity and therapeutic activity ( Figure 4 ). The specific manifestations are:

[0106] (1) Disease-resistant varieties (P5): Among the protective activities, hexaconazole had the best control effect, which was 40.31%, followed by carboxin, which was 21.71%, and azoxystrobin had the worst effect, which was only 6.2%. Among the curative activities, azoxystrobin had the best effect (20.93%), followed by fluazinam (10.85%), and hexaconazole had the worst effect (2.33%).

[0107] (2) Susceptible varieties (P9): Among the protective activities, azoxystrobin had the best effect (49.28%), followed by carboxin (33.33%), and fluazinam had the worst effect (9.42%). Among the curative activities, carboxin had the best effect (36.96%), followed by hexaconazole (34.78%), and fluazinam had the worst effect (8.7%).

[0108] 1.2.3 Effects of applying hexaconazole and azoxystrobin on pepper varieties resistant to and susceptible to white rot under white rot stress

[0109] 1.2.3.1 Determination of the control effect of hexaconazole and azoxystrobin on pepper varieties susceptible to white rot

[0110] According to 1.2.2.2, hexaconazole and azoxystrobin were selected as the final fungicide. Two pepper varieties (P5 and P9, which are disease-resistant and susceptible varieties, respectively) were treated with hexaconazole and azoxystrobin at CK (clean water treatment), 50μg / mL, and 100μg / mL concentrations of fungicides 24 hours before and after inoculation. The growth of peppers was observed 5 days after inoculation to test the control effect. The results are as follows: Figures 5-6 shown.

[0111] according to Figures 5-6 It can be seen that different resistant pepper varieties have different control effects when treated with the same fungicide. Hexaconazole and azoxystrobin significantly (P < 0.05) reduced the disease index of pepper white rot, and there was a significant difference in the control effect between pepper varieties resistant and susceptible to white rot (P < 0.05). Specifically:

[0112] (1) In pepper varieties resistant / susceptible to white rot, different fungicide dosage treatments had different control effects on white rot. Among them, the best control treatment for resistant varieties was hexaconazole protective activity 50μg / mL, with a control effect of 98.12%, followed by hexaconazole protective activity 100μg / mL and azoxystrobin protective activity 100μg / mL, with control effects of 92.58% and 88.60%, respectively; azoxystrobin therapeutic activity 50μg / mL had the lowest control effect, which was 8.47%. The best control treatment for susceptible varieties was azoxystrobin protective activity 100μg / mL, with a control effect of 85.41%, followed by azoxystrobin therapeutic activity 100μg / mL and hexaconazole protective activity 50μg / mL, with control effects of 82.97% and 74.77%, respectively; hexaconazole therapeutic activity 100μg / mL had the lowest control effect, which was 31.58%.

[0113] (2) Under the same fungicide treatment, the responses of pepper varieties resistant to and susceptible to white rot were different. In terms of protective activity, the control effects of hexaconazole and azoxystrobin on resistant varieties were significantly higher (P < 0.05) than those on susceptible varieties, while in terms of curative activity, except for hexaconazole 100 μg / mL, the control effects of the other treatments on susceptible varieties were significantly higher (P < 0.05) than those on resistant varieties. These results show that hexaconazole and azoxystrobin have good protective activity on pepper. Although there are certain differences in the activity effects between different varieties, and the curative activity is not as obvious as the protective activity, they still have a control effect on white rot of pepper, and overall, the control effect of resistant varieties is better than that of susceptible varieties.

[0114] (3) There were differences in the control effects between resistant and susceptible varieties of white rot, but overall, the protective activity of the fungicide was significantly better than the therapeutic activity. There were large differences in the protective and therapeutic effects of the resistant varieties, while the differences were smaller among the susceptible varieties. When hexaconazole was 50 μg / mL, the difference between the protective activity and the therapeutic activity of the two resistant varieties was the largest, with a difference of 74.84%, while the difference between the protective activity and the therapeutic activity of the susceptible variety was 42.25%; when hexaconazole was 100 μg / mL, the difference between the protective activity and the therapeutic activity of the two susceptible varieties was the largest, with a difference of 42.32%, while the difference between Qianjiao No. 8 (P5) was 57.24%; when azoxystrobin was 50 μg / mL, the difference between the protective activity and the therapeutic activity of the resistant varieties was still large, at 66.55%, but the difference between the control effects of the susceptible varieties was very small, only 8.60%; when azoxystrobin was 100 μg / mL, the differences in the protective activity and the therapeutic activity of the resistant and susceptible varieties were both the smallest, but the resistant variety still reached 36.96%, while the difference in the control effect of the susceptible variety was only 2.44%.

[0115] (4) In terms of protective activity, the disease index of the resistant variety CK was higher than that of the susceptible variety, but after the application of the pesticide, the control effect was significantly better than that of the susceptible variety; while in terms of curative activity, there was no significant difference in the CK disease index between the two, but the control effect of the susceptible variety under the azoxystrobin pesticide was significantly better than that of the resistant variety. This indicates that the resistant variety has a better absorption or retention effect on the pesticide in terms of protective activity, while the susceptible variety has a better curative activity, that is, the resistant and susceptible pepper varieties have different responses to different pesticides.

[0116] (5) After a significance level analysis of the interaction between different variety resistance, different fungicide treatments and protective / therapeutic activity on the control effect, it was found that variety resistance, fungicide treatment and protective / therapeutic activity all had a very significant effect on the control effect of pepper white rot (Table 2), indicating that there was a significant difference in the control effect of fungicides between pepper varieties resistant and susceptible to white rot, and it is feasible to use resistant varieties combined with fungicides to control white rot.

[0117] Table 2 Results of significance analysis of variety resistance, fungicide treatment and protective / curative activity on control effects

[0118]

[0119] Note: aR 2 =0.992 (adjusted R 2 =0.989).

[0120] 1.2.3.2 Effects of hexaconazole and azoxystrobin on root morphology of pepper varieties resistant to white rot and susceptible to white rot

[0121] The roots were scanned into TIF image files using Expression 12000xl root scanner (Epson, USA), and then the images were quantitatively analyzed using WinRHIZO image analysis software to obtain parameters such as total root length, root surface area, root volume, and average root diameter. The results showed that there were significant differences in root morphology under different fungicide and concentration treatments. Compared with the control without fungicide application, as the fungicide concentration increased, the inhibitory effect on white rot was enhanced, the control effect increased, and the stress of white rot on the pepper root system became less. The overall root morphology showed that the total root length, root projection area, root volume, root surface area, and number of root tips were significantly (P < 0.05) increased ( Figure 7 and Figure 8 ). Moreover, the root morphology of the resistant varieties after infection with S. rolfsii was still significantly better than that of the susceptible varieties without the application of fungicides. This is also the reason why the resistant varieties had significantly better control effects than the susceptible varieties in the protective activity, but the susceptible varieties were better than the resistant varieties in the therapeutic activity. That is, in the protective activity, the good and developed root system of the resistant varieties allowed them to absorb more pesticides, but in the therapeutic activity, the larger root area allowed the S. rolfsii to infect them more deeply, destroying the root system and reducing the subsequent absorption capacity of pesticides, while the opposite was true for the susceptible varieties.

[0122] 1.2.4 Effects of hexaconazole and azoxystrobin on root antioxidant enzyme activities in pepper varieties resistant to white rot and susceptible to white rot

[0123] As in step 1.2.3, relevant samples were collected 5 days after inoculation, and the following antioxidant enzyme activities were determined: POD activity (peroxidase), MDA (malondialdehyde), CAT activity (catalase), H2O2 (hydrogen peroxide), all using kits from Beijing Solebow Biotechnology Co., Ltd.

[0124] The results showed that the H2O2 content of the disease-resistant varieties under different fungicide treatments showed an upward trend compared with the control under protective activity, but the change was not much different under therapeutic activity compared with the control ( Fig. 9 a); CAT activity showed a decreasing trend with increasing fungicide concentration compared with the control under protective activity ( Fig. 9 b), and except for the CAT activity of 50 μg / mL of hexaconazole, which increased compared with the control, the CAT activity of the other fungicides decreased, and the MDA of the protective activity was higher than that of the control, and the therapeutic activity also showed the same trend ( Fig. 9 c). POD activity showed a downward trend compared with the control under protective activity, while the opposite trend was observed for therapeutic activity ( Fig. 9 (d)

[0125] The protective and curative activities of susceptible varieties under different fungicide treatments were compared with the control, and the H2O2 content under fungicide activity increased ( Fig.10 middle a); CAT activity decreased ( Fig.10 b); MDA content increased ( Fig.10 c); POD activity in the protective activity of the treatment of azoxystrobin 50 μg / mL was higher than that of the control group, and the others were lower than that of the control group. In the therapeutic activity, hexaconazole 50 μg / mL and azoxystrobin 100 μg / mL were lower than those of the control group, and the others were higher than those of the control group ( Fig.10 (d)

[0126] Under the same treatment of pesticides, the MDA content of resistant varieties was lower than that of susceptible varieties when the protective activity was observed; while the MDA content of resistant varieties was higher than that of susceptible varieties when hexaconazole was applied, but lower than that of susceptible varieties when azoxystrobin was applied. This is positively correlated with the control effect of the pesticide, that is, when the pesticide control effect on white rot is good, the degree of plant cell damage is small, indicating that the root antioxidant enzyme system of resistant varieties can be stimulated by the pesticide during the protective activity, so that the root system can be regulated in advance and defend in advance, further enhancing the resistance to white rot, while the white rot antioxidant enzyme system is attacked first during the therapeutic activity, and it is difficult to be absorbed and restore the system regulation after the pesticide acts, resulting in poor resistance to white rot.

[0127] 1.2.5 Correlation Analysis

[0128] Correlation analysis was performed between different indicators of resistant and susceptible varieties after inoculation. The analysis showed that there was a correlation between the disease index of resistant and susceptible varieties and different indicators. The results showed that the disease index of resistant varieties was negatively correlated with the control effect, average root diameter, root volume, root surface area, and H2O2, and positively correlated with the total root length, root projection area, number of root tips, CAT, MDA, and POD; while the disease index of susceptible varieties was positively correlated with POD, and negatively correlated with the other indicators ( Fig.11 ). This result indicates that the difference in control effect between resistant and susceptible varieties is caused by the inconsistent regulation between root morphology and root antioxidant enzyme system.

[0129] Based on the above content, it can be seen that hexaconazole and / or myclobutanil have good comprehensive prevention effect on pepper white rot. The use of resistant varieties and fungicides in combination for disease management can effectively reduce the incidence of white rot, reduce the amount of fungicides used, and maintain stable plant growth. In addition, the root morphology and antioxidant enzyme regulation of resistant varieties are better than those of susceptible varieties, and the protective activity control effect of resistant varieties is significantly higher than that of susceptible varieties.

[0130] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. The use of a fungicide in preventing and treating pepper white rot, characterized in that: The bactericide comprises hexaconazole and / or azoxystrobin; The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8; The use concentration of hexaconazole is 20 to 100 μg / mL; The use concentration of the azoxystrobin is 20-100 μg / mL.

2. The use according to claim 1, characterized in that: The disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435; The susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101.

3. The use according to claim 1, characterized in that: The bactericide inhibits the growth of pepper white rot pathogenic bacteria and prevents and controls pepper white rot.

4. The use according to claim 1, characterized in that: The dosage form of the hexaconazole is 95wt.% powder; the dosage form of the azoxystrobin is 98wt.% powder.

5. A method for preventing pepper white rot, characterized in that: Apply fungicide to peppers when the pepper seedlings are transplanted to the field; The bactericide comprises hexaconazole and / or azoxystrobin; The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8; The use concentration of hexaconazole is 20-100 μg / mL, and the application amount is 5 mL / plant; The use concentration of the azoxystrobin is 20-100 μg / mL, and the application amount is 5 mL / plant.

6. The method according to claim 5, characterized in that The fungicide is applied by root irrigation.

7. The method according to claim 5, characterized in that The disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435; The susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101.

8. A method for treating pepper white rot, characterized in that: Apply fungicide to peppers 24 hours after they are infected with pepper white rot pathogen; The bactericide comprises hexaconazole and / or azoxystrobin; The varieties of pepper include disease-resistant varieties and disease-susceptible varieties; the disease index of the disease-resistant varieties to white rot is ≤45.8; the disease index of the disease-susceptible varieties to white rot is >45.8; The use concentration of hexaconazole is 20-100 μg / mL, and the application amount is 5 mL / plant; The use concentration of the azoxystrobin is 20-100 μg / mL, and the application amount is 5 mL / plant.

9. The method according to claim 8, characterized in that The fungicide is applied by root irrigation.

10. The method according to claim 8, characterized in that The disease-resistant varieties include one or more of Qianjiao No. 8, Yanjiao 485 and Yanjiao 435; The susceptible varieties include one or more of Xiangla No. 7, Xiangla No. 14, Zunla No. 9, Layan No. 3, Layan No. 12 and Layan 101.

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