Application of lanthanum-based nanomaterial in controlling tomato bacterial wilt

Abstract

The application discloses application of a lanthanum-based nanometer material in control of tomato bacterial wilt and belongs to the technical field of pesticides. The lanthanum-based nanometer material is selected from any one or more of the following: LaPO4 nanorods (LaPO4 NRs), LaPO4 nanoparticles (LaPO4 NPs), La2S3 nanoparticles (La2S3 NPs) and La2O3 nanoparticles (La2O3 NPs). The tomato bacterial wilt is effectively controlled by foliar application of the lanthanum-based nanometer material, the growth of tomatoes is further promoted, and the incidence of the tomato bacterial wilt is significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of pesticide technology, specifically relating to the application of a lanthanum-based nanomaterial in controlling bacterial wilt of tomatoes. Background Technology

[0002] With the rapid increase in population, the demand for crop yields has increased significantly. Globally, crop diseases account for 20%-40% of annual crop yield losses each year. Currently, pesticides and fungicides are widely used to reduce the impact of crop pests and diseases. However, research has found that excessive use of pesticides leads to their accumulation in the environment, causing a series of problems such as soil degradation, increased pathogen resistance, toxicity to non-target organisms, and threats to human health. Therefore, there is an urgent need to develop a highly efficient, low-risk, and sustainable alternative to traditional pesticides for the effective control of crop diseases.

[0003] The development of nanotechnology has provided new possibilities for the efficient and sustainable control of crop diseases. At present, copper-based nanomaterials have shown great potential in the prevention and control of crop diseases. However, traditional copper-based pesticides have been widely used. Any form of copper-based pesticide will lead to the accumulation of Cu in the soil, causing soil pollution, and may even enable the target pathogens to acquire resistance. Summary of the Invention

[0004] To address the above technical problems and application objectives, this invention proposes a method for controlling bacterial wilt in tomatoes based on lanthanum-based nanomaterials (La-based NMs).

[0005] The technical solution of this invention is:

[0006] The main contents of this invention include: (1) preparing lanthanum-based nanomaterials of different forms and compositions (LaPO4 nanorods (NRs), LaPO4 nanoparticles (NPs), La2S3 nanoparticles (NPs), La2O3 nanoparticles (NPs)); (2) applying LaPO4 nanorods of different concentrations to tomatoes by foliar spraying to investigate their effect on controlling bacterial wilt of tomatoes; (3) applying lanthanum-based nanomaterials of different forms and compositions, lanthanum chloride of equal amount, phosphate of equal amount, and traditional pesticide (oxamyl) of agricultural guidance concentration to tomatoes by foliar spraying to investigate their effect on controlling bacterial wilt of tomatoes.

[0007] Specifically,

[0008] This invention provides an application of lanthanum-based nanomaterials in controlling bacterial wilt of tomatoes, wherein the lanthanum-based nanomaterials are selected from any one or more of the following: LaPO4 nanorods (LaPO4 NRs), LaPO4 nanoparticles (LaPO4 NPs), La2S3 nanoparticles (La2S3 NPs), and La2O3 nanoparticles (La2O3 NPs).

[0009] In one embodiment of the present invention, the application includes the following process: dispersing lanthanum-based nanomaterials in water to prepare a lanthanum-based nanomaterial suspension, and then applying the lanthanum-based nanomaterial suspension to tomatoes by foliar spraying.

[0010] In one embodiment of the present invention, the concentration of the lanthanum-based nanomaterial suspension is 50-200 mg / L; preferably 100 mg / L.

[0011] In one embodiment of the present invention, the LaPO4 nanorod has a length of 92.5±21.7 nm and a width of 11.6±2.3 nm.

[0012] In one embodiment of the present invention, the size of the LaPO4 nanoparticles is 110.9 ± 23.5 nm.

[0013] In one embodiment of the present invention, the size of the La2S3 nanoparticles is 38.6 ± 3.2 nm.

[0014] In one embodiment of the present invention, the size of the La2O3 nanoparticles is 55.5 ± 28.1 nm.

[0015] In one embodiment of the present invention, the method for preparing the LaPO4 nanorods includes: mixing n-butanol and aqueous solutions of Na3PO4 and LaCl3, adjusting the pH to 6.0-7.0 to obtain a mixed solution; stirring the mixed solution until a white gel-like substance is formed, and then heating and reacting at 150-200°C for 20-30 hours; after the reaction is completed, separating and collecting the solid, washing it, and obtaining LaPO4 nanoparticles.

[0016] In one embodiment of the present invention, the method for preparing the LaPO4 nanoparticles includes: mixing n-butanol and aqueous solutions of Na3PO4 and LaCl3, adjusting the pH to 6.0-7.0 to obtain a mixed solution; stirring the mixed solution until a white gel-like substance is formed, and then heating the mixture at 150-200°C for 5-8 hours; after the reaction is completed, separating and collecting the solid, washing it, and obtaining LaPO4 nanoparticles.

[0017] In one embodiment of the present invention, the concentration of the Na3PO4 aqueous solution is 0.25M; the concentration of the LaCl3 aqueous solution is 2mM.

[0018] In one embodiment of the present invention, the volume ratio of n-butanol, Na3PO4 aqueous solution, and LaCl3 aqueous solution is 1:2:2.

[0019] In one embodiment of the present invention, the method for preparing the La2S3 nanoparticles includes: adding LaCl3·7H2O and Na2S2O3·5H2O to PEG-400, mixing them, and heating them at 80°C for 30 min; then placing them at 90°C to continue the reaction for 24 h, and after the reaction is completed, separating and collecting the solid, washing it, and obtaining La2S3 nanoparticles.

[0020] In one embodiment of the present invention, the mass ratio of LaCl3·7H2O to Na2S2O3·5H2O is (1.5-2.5):1.

[0021] In one embodiment of the present invention, the amount of PEG-400 relative to Na2S2O3·5H2O is (10-15) mL / g.

[0022] In one embodiment of the present invention, the method for preparing the La2O3 nanoparticles includes: adding NaOH solution dropwise into an aqueous solution of LaCl3·7H2O, adjusting the pH to 11 to obtain a white precipitate La(OH)3, washing it, suspending it in water to obtain a La(OH)3 suspension, then heating it at 200°C for 8 hours, separating and collecting the solid, washing it, and freeze-drying it to obtain La2O3 nanoparticles.

[0023] The present invention has the following beneficial technical effects:

[0024] This invention effectively controls bacterial wilt in tomatoes and further promotes tomato growth through foliar application of lanthanum-based nanomaterials. The incidence of bacterial wilt in tomatoes is reduced to as low as 25%. Furthermore, among different lanthanum-based nanomaterials, the effectiveness in controlling bacterial wilt in tomatoes is as follows: LaPO4 NPs > LaPO4 NRs ≈ La2S3 NPs > La2O3 NPs > La ions > P ions ≈ oxadixyl. Attached Figure Description

[0025] Figure 1 A is a TEM image of LaPO4 NRs; B is a TEM image of LaPO4 NPs; C is a TEM image of La2S3 NPs; D is a TEM image of La2O3 NPs; E, F, G, and H are XRD spectra of LaPO4 NRs, LaPO4 NPs, La2S3 NPs, and La2O3 NPs, respectively.

[0026] Figure 2The effects of applying different concentrations of LaPO4 NRs to the leaves on the aboveground and underground biomass (A) and disease index (B) of tomatoes.

[0027] Figure 3 The effects of foliar application of 100 mg / L LaPO4 NRs, LaPO4 NPs, La2S3 NPs, La2O3 NPs, chloride (LaCl3), phosphate (Na3PO4) and 300 mg / L oxamyl on aboveground and underground biomass (A) and disease index (B) of tomatoes. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] The embodiments provided below are not intended to limit the scope of this invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to this invention by those skilled in the art in conjunction with existing common knowledge also fall within the scope of protection claimed by this invention.

[0030] Example 1: Preparation of Lanthanum-based Nanomaterials

[0031] 4 mL of n-butanol and 8 mL of Na3PO4 aqueous solution (0.25 M) were added to 8 mL of LaCl3 aqueous solution (2 m M), mixed well, and the pH of the mixture was adjusted to 6.5 using 0.1 M NaOH solution and HCl solution to obtain a mixed solution. The mixture was stirred at 400 rpm / min for 30 minutes until a white gel-like substance was formed, and then transferred to a 50 mL stainless steel reactor lined with polytetrafluoroethylene. Subsequently, it was heated in an oven at 180 °C for 24 h and 6 h, respectively. After the treatment, the solid was separated and collected, and washed 5 times with ethanol and deionized water to prepare LaPO4 nanorods (LaPO4 NRs) and LaPO4 nanoparticles (LaPO4 NPs).

[0032] 1.35 g LaCl3·7H2O and 0.78 g Na2S2O3·5H2O were added to 10 mL PEG-400. The mixture was then stirred at 400 rpm / min and heated at 80 °C for 30 min, followed by further heating in an oven at 90 °C for 24 h. The resulting precipitate was washed three times with methanol, ethanol and deionized water, respectively, to obtain La2S3 nanoparticles (La2S3NPs).

[0033] NaOH solution (1M) was added dropwise to 100 mL of LaCl3·7H2O (100 mM) solution until the pH value reached 11. The resulting white precipitate (La(OH)3) was washed 5 times with deionized water and suspended in 100 mL of deionized water. The La(OH)3 suspension was transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and heated at 200 °C for 8 h. Then it was washed 6 times with DI water and 75% ethanol, respectively, and freeze-dried for 12 h to obtain La2O3 nanoparticles (La2O3 NPs).

[0034] Characterization:

[0035] The morphology and size of LaPO4 NRs, LaPO4 NPs, La2S3 NPs, and La2O3 NPs were characterized using transmission electron microscopy (TEM). The results showed that LaPO4 NRs were rod-shaped, with a length of 92.5 ± 21.7 nm and a width of 11.6 ± 2.3 nm; LaPO4 NPs, La2S3 NPs, and La2O3 NPs all exhibited spherical morphology, with dimensions of 110.9 ± 23.5 nm, 38.6 ± 3.2 nm, and 55.5 ± 28.1 nm, respectively. Figure 1 (As shown). The XRD spectra of LaPO4 NRs, LaPO4 NPs, La2S3 NPs and La2O3 NPs show the characteristic peaks of LaPO4, LaPO4, La2S3 and La2O3 (see...). Figure 1 ).

[0036] Example 2: Application of lanthanum-based nanomaterials to control bacterial wilt in tomatoes

[0037] The LaPO4 NRs obtained in Example 1 were dispersed in water to prepare LaPO4 NRs suspensions of 50, 100, and 200 mg / L.

[0038] Tomato (Solanum lycopersicum L.) was used as the test crop, and the pathogen of tomato bacterial wilt was Ralstonia solanacearum. A group of tomato seeds were sown in pots containing 600g of soil. At week 6 of growth, 5mL of 50, 100, and 200mg / L LaPO4 NRs suspensions were sprayed onto the tomato leaves. Three days later, 10mL of Ralstonia solanacearum suspension (OD600=1) was added to each pot via root irrigation to induce pathogen infection. After week 7 of growth, another 5mL of suspension was sprayed onto the tomato leaves for a second application. At week 10 of growth, the severity of the disease was assessed, and destructive samples were taken from the tomatoes, weighing the fresh weight of the above-ground and underground parts.

[0039] The uninfected treatment group was designated as the healthy control group, while the treatment group treated with 0 mg / L was designated as the infected control group. The severity of tomato disease (disease level) was classified into five grades: Grade 0, no symptoms; Grade 1, one wilted leaf; Grade 2, two to three wilted leaves; Grade 3, all leaves except the top two to three wilted leaves; Grade 4, all leaves on the plant wilted.

[0040] The formula for calculating the incidence rate of tomatoes is as follows: Where s is the representative value of each disease level; n is the number of plants at each disease level; S is the representative value of the highest disease level (S=4); and N is the total number of plants surveyed (N=6).

[0041] Aboveground biomass refers to the mass of fresh tomato stems and leaves, while underground biomass refers to the mass of fresh tomato roots.

[0042] The results showed that the fresh weight of the aboveground and underground parts of tomatoes in the diseased group was significantly lower than that in the healthy group, decreasing by 50.6% and 55.3%, respectively (see Table 1 for details). Foliar application of 100 mg / L LaPO4 NRs exhibited the best control effect against tomato bacterial wilt, with the aboveground and underground fresh weights being 2.14 and 2.57 times that of the diseased group, respectively, while reducing the incidence of tomato bacterial wilt by 75%. Therefore, 100 mg / L is the optimal concentration of LaPO4 NRs for controlling tomato bacterial wilt (see Table 2 for details).

[0043] Table 1 Results of tomato biomass treatment with different concentrations of LaPO4 NRs

[0044] Processing group Aboveground parts (g) Underground part (g) Health comparison 7.51 1.22 Disease control 3.71 0.55 <![CDATA[50mg / L LaPO4 NRs]]> 5.87 1.01 <![CDATA[100mg / L LaPO4 NRs]]> 7.94 1.41 <![CDATA[200mg / L LaPO4 NRs]]> 6.73 1.12

[0045] Table 2 Results of controlling bacterial wilt in tomato with different concentrations of LaPO4 NRs

[0046] <![CDATA[Concentration of LaPO4 NRs suspension (mg / L)]]> Incidence rate (%) 0 93.33 50 86.67 100 26.67 200 43.33

[0047] Example 3: Application of lanthanum-based nanomaterials to control bacterial wilt in tomatoes

[0048] The LaPO4 NRs, LaPO4 NPs, La2S3 NPs and La2O3 NPs obtained in Example 1, as well as chloride (LaCl3) and phosphate (Na3PO4), were dispersed in water to prepare suspensions of different materials at 100 mg / L.

[0049] Another group of tomato seeds were sown in pots containing 600g of soil. At week 6, the tomato leaves were sprayed with 5mL of a suspension containing 100mg / L LaPO4 NRs, LaPO4 NPs, La2S3 NPs, La2O3 NPs, chloride (LaCl3), phosphate (Na3PO4), and 300mg / L oxadixyl. Three days later, 10mL of a suspension of *Alstonia solanacearum* (OD600=1) was added to each pot via root drenching to induce pathogen infection. After week 7, another 5mL of suspension was sprayed onto the tomato leaves for a second application. At week 10, the severity of the disease was assessed, and samples of damaged tomatoes were weighed, including the above-ground and underground parts.

[0050] The results showed that foliar spraying of LaPO4 NRs, LaPO4 NPs, La2S3 NPs, La2O3 NPs, and LaCl3 significantly increased the aboveground biomass of tomatoes compared to the diseased group, while Na3PO4 and oxadixyl had no significant effect on the aboveground biomass of tomatoes. Figure 3 Foliar application of LaPO4 NRs, LaPO4 NPs, La2S3 NPs, and oxadixyl significantly increased the underground biomass of tomatoes compared to the diseased group, while La2O3 NPs, LaCl3, and Na3PO4 had no significant effect on the underground biomass of tomatoes. Figure 3 The specific results are shown in Table 3. Foliar spraying of LaPO4 NRs, LaPO4 NPs, La2S3 NPs, La2O3 NPs, and LaCl3 all significantly reduced the incidence of bacterial wilt in tomatoes. Among them, the control effect of LaPO4 NPs on bacterial wilt in tomatoes was 1.23, 1.21, 2.12, and 4.58 times that of LaPO4 NRs, La2S3 NPs, La2O3 NPs, and LaCl3, respectively. Figure 3 The results show that LaPO4 NPs are the most effective at controlling bacterial wilt in tomatoes, and significantly superior to the control effect of the traditional pesticide hymexazol. Specific results are shown in Table 4.

[0051] Table 3 Results of tomato biomass treated with different materials

[0052] Processing group Aboveground parts (g) Underground part (g) Health comparison 8.46 1.42 Disease control 3.80 0.63 <![CDATA[LaPO4 NRs]]> 9.01 1.76 <![CDATA[LaPO4 NPs]]> 9.73 1.87 <![CDATA[La2S3 NPs]]> 7.60 1.59 <![CDATA[La2O3 NPs]]> 5.60 0.67 <![CDATA[LaCl3]]> 6.09 0.79 <![CDATA[Na3PO4]]> 4.52 0.75 Oxyphenidyl 5.25 1.21

[0053] Table 4 Results of different materials in controlling bacterial wilt in tomato

[0054] Application materials Incidence rate (%) <![CDATA[LaPO4 NRs]]> 25 <![CDATA[LaPO4 NPs]]> 11.67 <![CDATA[La2S3 NPs]]> 24.17 <![CDATA[La2O3 NPs]]> 50 <![CDATA[LaCl3]]> 68.33 <![CDATA[Na3PO4]]> 75.83 Oxyphenidyl 66.67

[0055] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined in the claims of this invention.

Claims

1. A method for controlling tomato bacterial wilt and promoting tomato growth, characterized in that, comprising the following process: preparing lanthanum-based nanomaterial suspension by dispersing lanthanum-based nanomaterial in water, and then applying the lanthanum-based nanomaterial suspension to tomato by foliar spraying; the lanthanum-based nanomaterial is selected from any one or more of the following: LaPO4 nanorods, LaPO4 nanoparticles, La2S3 nanoparticles; the concentration of the lanthanum-based nanomaterial suspension is 100 mg / L; the preparation method of the LaPO4 nanorods comprises: mixing n-butanol and Na3PO4 aqueous solution, LaCl3 aqueous solution, adjusting the pH to 6.0-7.0 to obtain a mixed solution; stirring the mixed solution until a white gel-like substance is formed, then heating the reaction at 150-200°C for 20-30h, after the reaction is completed, separating and collecting the solid, washing to obtain LaPO4 nanorods; the preparation method of the LaPO4 nanoparticles comprises: mixing n-butanol and Na3PO4 aqueous solution, LaCl3 aqueous solution, adjusting the pH to 6.0-7.0 to obtain a mixed solution; stirring the mixed solution until a white gel-like substance is formed, then heating the reaction at 150-200°C for 5-8h, after the reaction is completed, separating and collecting the solid, washing to obtain LaPO4 nanoparticles; the preparation method of the La2S3 nanoparticles comprises: adding LaCl3·7H2O and Na2S2O3·5H2O into PEG-400, mixing uniformly, and heating the reaction at 80°C for 30min; then placing it at 90°C for 24h, after the reaction is completed, separating and collecting the solid, washing to obtain La2S3 nanoparticles.

2. The method of claim 1, wherein, The length of the LaPO4 nanorods is 92.5±21.7nm, and the width is 11.6±2.3nm.

3. The method of claim 1, wherein, The size of the LaPO4 nanoparticles is 110.9±23.5nm.

4. The method of claim 1, wherein, The size of the La2S3 nanoparticles is 38.6±3.2nm.

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