Application of polyether compounds in preventing and treating plant diseases caused by Xanthomonas

Abstract

The present invention relates to the application of polyether compounds as fungicides in controlling plant diseases caused by Xanthomonas, specifically, the polyether compounds are one or more of nigericin, lasalocid and nanchangmycin, which have a stronger inhibitory effect on Xanthomonas than the currently commonly used commercial drugs bismerthiazol and thiodiazole copper, and have good development prospects.

Description

Technical Field

[0001] The present invention belongs to the field of pesticide science, and particularly relates to the application of polyether compounds as fungicides in controlling plant diseases caused by Xanthomonas bacteria. Background Art

[0002] Xanthomonas is a general term for bacteria of the genus Xanthomonas. Most members are plant pathogenic bacteria and can infect more than 400 food crops and cash crops, including rice, wheat, citrus, tomato, soybean, cruciferous vegetables, and oil crops. Xanthomonas campestris pv. campestris is the pathogen of black rot of cruciferous plants, and Xanthomonas oryzae pv. oryzae is the pathogen of bacterial blight of rice. They are the most representative plant pathogens among Xanthomonas bacteria and have a serious impact on the production of rape and rice. At present, there are problems such as a lack of chemical agents and unsatisfactory control effects in the prevention and control of plant diseases caused by Xanthomonas. Moreover, the long-term and unreasonable use of existing common chemical agents, such as bismerthiazol and thiodiazole copper, has led to a series of problems such as an increase in the drug resistance of pathogenic bacteria and damage to the ecological environment, which has attracted great attention. Therefore, there is an urgent need to develop new green agents with high efficiency and low toxicity for the prevention and control of plant diseases caused by Xanthomonas.

[0003] Most polyether antibiotics are polyketide compounds produced by Streptomyces. Because of their cation carrier properties, they are also called ionophore compounds. Polyether compounds have strong anticoccidial activity and are not prone to drug resistance. Cross-resistance is not easily generated among polyether antibiotics either. Therefore, they are widely used in the treatment of animal coccidiosis. For example, monensin, salinomycin, maduramycin, lasalocid, and fusidic acid have been used for the treatment and prevention of coccidiosis in chickens; monensin and others can also be used as livestock feed additives, which can promote growth and control diseases. In addition, polyether compounds also have activities against tumors, viruses, and Gram-positive bacteria, but have little or very weak activity against Gram-negative bacteria. At present, there is no research report on the antibacterial activity of polyether compounds against the Gram-negative bacterium Xanthomonas. Summary of the Invention

[0004] The present invention provides the application of polyether compounds as fungicides or bacteriostatic agents in controlling plant diseases caused by Xanthomonas.

[0005] The polyether compounds involved in the present invention are one or more of nigericin, lasalocid, and nanchangmycin.

[0006] The present invention also relates to the above-mentioned polyether compounds or their stereoisomers, or their salts or solvates, or compositions containing said compounds, which can be used for preventing and controlling plant diseases caused by Xanthomonas. Preferably, the plant diseases are caused by one or more of Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicola, Xanthomonas oryzae pv. citri, Xanthomonas fragariae, Xanthomonas campestris pv. campestris, and Xanthomonas campestris pv. mangiferaeindicae.

[0007] Compared with the prior art, the present invention has the following beneficial effects:

[0008] There is currently no report on the inhibition of Xanthomonas by polyether compounds. The polyether compounds described in the present invention have a stronger inhibitory effect on Xanthomonas than the currently commonly used commercial drugs bismerthiazol and thiodiazole copper, and can be developed into a new type of bacteriostatic or fungicidal agent to replace bismerthiazol and thiodiazole copper for preventing and controlling plant diseases caused by Xanthomonas. Description of the Drawings

[0009] Figure 1 Pot control effects of nigericin, bismerthiazol, and thiodiazole copper on bacterial leaf blight of rice. Detailed Embodiments

[0010] The following examples further illustrate the present invention but do not limit the present invention. All other examples obtained by those of ordinary skill in the art based on the examples in the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0011] Example 1: Activity determination of polyether compounds against the plant pathogen Xanthomonas

[0012] The turbidimetry method was used to test the inhibition rate of polyether compounds against plant pathogenic bacteria. The test objects were Xanthomonas oryzae pv. oryzae, Xanthomonas oryzae pv. oryzicola, Xanthomonas oryzae pv. citri, Xanthomonas fragariae, Xanthomonas campestris pv. campestris, and Xanthomonas campestris pv. mangiferaeindicae.

[0013] After activating the above microbial strains on PSA plates, a single colony was picked up with a bamboo stick and inoculated into PSA liquid medium, and then placed in a constant temperature shaker at 28 °C and shaken at 200 rpm for 24 h. After the bacterial liquid grew to the logarithmic growth phase, the OD 600 of the bacterial liquid was adjusted to 0.5, and it was diluted 10 times to prepare a bacterial liquid of 2×10 7 cfu / mL for standby. 190 μL of the prepared PSA liquid medium was pipetted and added dropwise to the first well of a 96-well plate, and then 100 μL of PSA liquid medium was added dropwise to the other 7 wells in the same row. 10 μL of the prepared stock solution of various antibiotics was added to the first well, and the agent was mixed with the liquid medium using a pipette. Each group had 3 replicates. Using the two-fold dilution method, 100 μL of the liquid medium and compound mixture in the first well was pipetted into the second well and mixed evenly, and then 100 μL of the mixture in the second well was pipetted into the third well, and so on, and the gradient dilution was carried out to the eighth well in turn. After thorough mixing in the last well, 100 μL was pipetted and discarded. 90 μL of liquid medium was added to each of the wells 1-8, and then 10 μL of bacterial liquid was added to each well to make the total volume of each well 200 μL. Each group was repeated three times. The liquid medium was used as the blank control, and the medium liquid with added bacterial liquid was used as the positive control. Each group was measured three times. The 96-well plate was sealed with a sealing film and incubated in an incubator for 24 hours.

[0014] The OD values of the liquid medium, Xoo solution, and compound treatment groups in the 96-well plate were measured with an enzyme-linked immunosorbent assay (ELISA) reader at a wavelength of 600 nm. When the OD value in the well was 0.05 higher than the OD value of the blank control, it was judged that bacteria grew. On the contrary, if the bacteria did not grow, the minimum inhibitory concentration (MIC) of the compound was judged accordingly. According to the inhibitory effects of polyether compounds at different concentrations on Xanthomonas, SPSS software was used to calculate the EC 50The results of the experimental study on the inhibitory effect of polyether compounds on Xanthomonas are shown in Table 1. As can be seen from the results in Table 1, the inhibitory effect of the polyether compounds of the present invention on Xanthomonas is significantly stronger than that of commercial agents thiophanate-methyl and chlorpyrifos, showing excellent antibacterial activity.

[0015] Table 1 Inhibitory activity of polyether compounds against Xanthomonas

[0016]

[0017] Example 2: Experimental study on the efficacy of polyether compound nigericin in inhibiting rice bacterial blight

[0018] Rice seeds were disinfected with sodium hypochlorite for 5 minutes, then rinsed with clean water to remove any residual sodium hypochlorite on the surface. The disinfected seeds were placed in a 55°C water bath for 30 minutes and then soaked overnight in a 28°C constant-temperature incubator. The seeds were then spread flat on moistened sterile filter paper and placed in a 28°C constant-temperature incubator for germination. After germination, the seeds were sown in pots and incubated in a 28°C constant-temperature, light-flooded incubator until the leaves reached 20 cm in length.

[0019] (1) Protection effectiveness test

[0020] The protective effect of nigericin on rice bacterial leaf blight in living potted plants was tested by the leaf cutting method. First, nigericin was prepared into a solvent with a concentration of 200μg / mL for use. The chemical pesticides thiophanate-methyl (20% effective dose) and thiophanate-methyl (20% active ingredient) commonly used on the market for rice bacterial leaf blight were used as positive controls. They were also prepared into a solution with an effective concentration of 200μg / mL for use. The blank control was an aqueous solution with the same volume of DMSO. The agent was applied to the surface of the rice leaves with a small spray bottle until the droplets began to drip downwards; the rice pot was placed in a light incubator and cultured for 24h. Use sterile scissors to dip the OD 600 After inoculating with a 0.8% solution of rice bacterial blight, the top of the rice leaf was cut and inoculated 1 cm away from the tip, and the wound of the leaf was placed in the rice bacterial blight solution and soaked for 30 seconds. Three replicates were set up for each group. After 14 days of cultivation, the disease status of each group was counted, and the prevention and control effect was calculated according to the length of the lesions on the leaves of each group.

[0021]

[0022]

[0023] (2) Treatment and prevention efficacy test

[0024] The leaf cutting method was used to determine the therapeutic effect of the target nigericin on rice bacterial blight in living pots.600 After inoculating with a Xanthomonas oryzae pv. oryzae solution with a concentration of about 0.8, leaf shearing inoculation was carried out 1 cm from the tip of the rice leaf at the top of the rice leaf, and the wound of the leaf was immersed in the Xanthomonas oryzae pv. oryzae solution for 30 s; after culturing the rice in a constant temperature light incubator for 24 h, nigericin and the positive control agent thiodiazole copper (20% effective dose) and bismerthiazol (20% effective dose) were respectively formulated into solutions with an effective concentration of 200 μg / mL. The blank control was an aqueous solution with the same volume of DMSO added. The agent was applied to the surface of the rice leaf with a small sprayer until the droplets began to drip down and then stopped. Three replicates were set. After culturing for 14 d, the disease incidence of each group was counted, and the control effect was calculated according to the length of the lesions on the leaves of each group.

[0025]

[0026]

[0027] Table 2 Pot control efficacy of polyether compound nigericin, bismerthiazol and thiodiazole copper against Xanthomonas oryzae pv. oryzae

[0028]

[0029] Note: Different letters indicate significant differences in means after Duncan's test, P < 0.05.

[0030] As can be seen from Table 2 and Figure 1 it can be seen that nigericin has a good control effect against Xanthomonas oryzae pv. oryzae. Compared with the control group, the control efficacy of nigericin reached 64.75%, and the treatment effect reached 60.38%. The control efficacies of the commercial agents bismerthiazol and thiodiazole copper were 44.4% and 48.16% respectively, and the treatment effects were 50.54% and 56.98% respectively. The treatment effect and control efficacy of nigericin against Xanthomonas oryzae pv. oryzae were both better than those of bismerthiazol and thiodiazole copper.

Claims

1. Use of polyether compounds in controlling plant diseases caused by Xanthomonas spp., where the Xanthomonas spp. are Xanthomonas oryzae pv. oryzae ), Xanthomonas oryzae pv. oryzicola Xanthomonas oryzae pv. oryzicola ), Xanthomonas citri subsp. citri Xanthomonas oryzae pv. citri ), Xanthomonas fragariae Xanthomonas fragariae ), Xanthomonas campestris pv. campestris Xanthomonas campestris pv. campestris ), and Xanthomonas axonopodis pv. mangiferaeindicae Xanthomonas campestris pv. mangiferaeindicae ), and the polyether compounds are one or more of nigericin, lasalocid, and nanchangmycin.

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