Composition containing PHA (polyhydroxyalkanoate) and potassium phosphite as well as preparation method and application of composition

Abstract

The invention relates to the technical field of biology, and particularly discloses a composition containing PHA (polyhydroxyalkanoate) and potassium phosphite as well as a preparation method and application of the composition. Research finds that after PHA which is commonly used as a mulching film material and potassium phosphite are compounded according to a specific proportion, the antibacterial, disease-preventing and growth-promoting effects of the potassium phosphite can be remarkably improved, the soil environment can be better improved, the soil EC value can be better reduced, and the soil organic matter content and phosphorus content can be better improved, so that the composition is provided. The fertilizer comprises PHA (polyhydroxyalkanoate) and potassium phosphite, the mass ratio of the PHA to the potassium phosphite is 1: (0.2-1.25). The composition provided by the invention provides a new effective promotion mode for crop cultivation, and is beneficial to yield increase.

Description

Technical Field

[0001] This invention relates to the field of biotechnology, and more specifically, to a composition comprising PHA and potassium phosphite, a method for its preparation, and its application. Background Technology

[0002] Soil-borne diseases refer to diseases caused by pathogens such as fungi, bacteria, nematodes, and viruses that live in the soil with diseased plant debris and invade crops through the roots or stems when conditions are suitable. More than 100 diseases have been identified in greenhouse-grown vegetables such as melons, solanaceous vegetables, and beans, with over 50 being frequently occurring and causing significant damage. Among these diseases, the vast majority are fungal and bacterial, and some are viral, with the pathogens overwintering in the soil or via diseased plant debris. The incidence of soil-borne diseases is becoming increasingly severe; after 3-5 years of continuous cultivation, crop yield and quality are seriously affected, making it a prominent problem in agricultural production.

[0003] Potassium phosphite is a compound that combines fertilizer and fungicidal functions. Its trivalent phosphorus content can inhibit the growth of soil-borne pathogens (such as Phytophthora and Downy mildew) by inducing systemic resistance (SAR) in plants. Experiments have confirmed that potassium phosphite has an inhibition rate of 40%-60% against citrus canker. However, in practical applications, it requires multiple applications, and its effectiveness in controlling soil-borne diseases is not ideal. Furthermore, excessive application often leads to soil compaction and salinization.

[0004] Therefore, it is necessary to conduct further research on how to improve the effectiveness of fertilizers. Summary of the Invention

[0005] One of the objectives of this invention is to provide a composition that can improve the crop's resistance to soil-borne diseases and effectively promote crop growth and improve the soil environment.

[0006] The present invention provides a composition comprising: PHA and potassium phosphite; wherein the mass ratio of PHA to potassium phosphite is 1:(0.2-1.25).

[0007] Preferably, the mass ratio of PHA to potassium phosphite is 1:(0.4-1), more preferably 1:(0.8-0.82).

[0008] This invention has found that when PHA, which is commonly used as a mulch film material, is compounded with potassium phosphite in a specific ratio, the antibacterial and growth-promoting effects of potassium phosphite can be significantly enhanced, and the soil environment can also be improved.

[0009] In specific applications of the composition of this invention, compared with the use of potassium phosphite or PHA alone, it can effectively reduce the disease index of various crops, improve the control effect of various pathogens, promote crop growth, increase yield, reduce soil EC value, and improve soil fertility (organic matter and phosphorus content), making it more suitable for crop growth.

[0010] The polyhydroxyalkanoate (PHA) of the present invention can be produced by microbial fermentation, and specifically, it contains the structural unit represented by the following general formula I: [CHR1(CH2)] X [COO] General Formula I; Wherein, R1 is a straight-chain or branched alkyl group represented by CpH2p+1, p is an integer from 1 to 15, preferably an integer from 1 to 10, more preferably an integer from 1 to 8; R1 is preferably methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, pentyl or hexyl; x is 1, 2 or 3.

[0011] When x=1, general formula I represents a 3-hydroxyalkanoate structural unit; when x=2, general formula I represents a 4-hydroxyalkanoate structural unit; and when x=3, general formula I represents a 5-hydroxyalkanoate structural unit. Among these, the 3-hydroxyalkanoate and 4-hydroxyalkanoate structural units are more common, such as the 3-hydroxybutyrate structural unit (hereinafter sometimes referred to as 3HB) and the 4-hydroxybutyrate structural unit (hereinafter sometimes referred to as 4HB).

[0012] The polyhydroxyalkanoate (PHA) according to the present invention comprises at least one poly(3-hydroxyalkanoate); the poly(3-hydroxyalkanoate) contains only 3-hydroxybutyrate structural units, or contains 3-hydroxybutyrate structural units and other hydroxyalkanoate structural units; The other hydroxyalkanoate structural units include one or more of 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynonanoate, 3-hydroxydecanoate, 3-hydroxyundecanoate, or 4-hydroxybutyrate; preferably, the other hydroxyalkanoate structural unit is 3-hydroxyhexanoate.

[0013] According to the polyhydroxyalkanoate composition provided by the present invention, the poly(3-hydroxyalkanoate) is selected from one or more of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0014] The PHA used in this invention is produced by microbial fermentation.

[0015] The microorganisms involved in the fermentation production of PHA are diverse, mainly distributed among bacteria, including: *Cupriavidus* (Ralstonia), such as *Cupriavidus necator* (Ralstonia eutropha); *Pseudomonas*, such as *Pseudomonas putida* and *Pseudomonas aeruginosa*; *Halomonas*, such as *Halomonas campaniensis* and *Halomonas bluephagenesis*; methylotrophs, such as *Methylobacterium extorquens* and *Methylomonas methanica*; *Bacillus*, such as *Bacillus megaterium* and *Bacillus cereus*; *Azotobacter*, such as *Azotobacter vinelandii* and *Azotobacter chroococcum*; and photosynthetic bacteria (such as *Rhodospirillum rubrum* and *Rhodobacter*). Sphaeroides; and other microorganisms, such as extreme environment microorganisms: such as thermophilus or acidophilus; recombinant engineered bacteria: such as genetically modified Escherichia coli and yeast, which can produce PHA.

[0016] The PHA used in this invention includes PHA existing in the form of vesicular inclusion bodies, as well as PHA powder and PHA granules prepared by extraction; the particle size range of the PHA powder or granules used in this invention is 0.1μm~500μm; preferably 0.5μm~300μm; more preferably 0.5μm~180μm.

[0017] PHA typically exists as vesicular inclusion bodies within the cells of the producing bacteria. It is extracted from the fermentation broth to prepare PHA powder or granules. Currently, PHA is commonly used in the form of extracted powders or granules, but the extraction process disrupts the vesicular inclusion body structure. PHA in vesicular inclusion body form exists in the fermentation broth, bacterial suspension, or bacterial precipitate of PHA-producing bacteria.

[0018] Vesicular inclusion bodies (PHAs) can be prepared using conventional methods. For example, the fermentation broth of PHA-producing bacteria is subjected to solid-liquid separation, the bacterial cells are collected, and after washing or without washing, resuspended in a solvent (e.g., water or buffer solution), and then sterilized to obtain a bacterial suspension.

[0019] Vesicular inclusion bodies (PHA) can also be provided as sterile fermentation broth without PHA extraction.

[0020] Preferably, in the composition of the present invention, the PHA is selected from poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), and the weight-average molecular weight of the PHBH is 100,000 to 1,000,000 Da; more preferably 200,000 to 900,000 Da; further preferably 300,000 to 800,000 Da; even more preferably 600,000 to 800,000 Da, and the potassium phosphite is potassium dihydrogen phosphite.

[0021] The composition of the present invention also includes a carrier, preferably glucose powder.

[0022] When the composition of the present invention is used as a fertilizer, in addition to organic fertilizer, inorganic fertilizer and organic-inorganic compound fertilizer, other common fertilizer carriers can also be selected to facilitate the dispersion of active ingredients, facilitate measurement and application, etc. Those skilled in the art can choose according to actual needs and costs.

[0023] The specific ratio of carrier and active ingredient added can be selected by those skilled in the art based on common knowledge in the field and application requirements (e.g., 20-80%), and the present invention does not impose any particular restrictions on this.

[0024] Furthermore, the composition may also include stabilizers and other additives commonly used in the art.

[0025] If synergistic components can be added, specifically 0.1% - 0.5% of diatomaceous earth-supported Bacillus subtilis spores (10...8 (CFU / g), further enhancing the control effect against soil-borne diseases.

[0026] The additive can be a surfactant, and the surfactant can be of different types, such as nonionic surfactant, anionic surfactant or cationic surfactant.

[0027] Stabilizers can be of different types, such as antioxidants and chelating agents, as long as they can improve the stability and effectiveness of the composition.

[0028] The present invention also provides a method for preparing the above composition, which includes the step of thoroughly mixing PHA and potassium phosphite.

[0029] Furthermore, the compositions of the present invention can be prepared as fertilizer formulations such as powders, liquids, and granules.

[0030] As one specific implementation method, the core components of the powder include: PHA powder: purity ≥80%, prepared by microbial fermentation, molecular formula [CHR1(CH2)] X [COO] (R1 is a C1-C8 alkyl group, X=1-3).

[0031] Potassium phosphite powder: mainly uses potassium dihydrogen phosphite, with a purity of ≥98%, conforming to HG / T 5517-2019 standard, and pH 5.5-6.5.

[0032] Mass ratio: The mass ratio of PHA powder to potassium phosphite powder is 1:0.2, 1:0.4, 1:0.8, 1:1, 1:2, with 1:0.8 being preferred.

[0033] Auxiliary ingredients: Add 0.5%-2% magnesium sulfate (anti-caking agent) or 0.5%-1% humic acid powder (soil conditioner).

[0034] Carrier powders: organic fertilizer powder, humic acid fertilizer powder, etc.

[0035] Powder preparation methods include: Raw material pretreatment: 98% potassium phosphite powder and 80% PHA powder are pulverized separately; Core mixing: Add to a dual cone mixer in proportion and mix at 30 rpm for 30 minutes; Additives: Add humic acid powder and magnesium sulfate, and continue mixing for 15 minutes; Extrusion granulation: granulation under 3-5 MPa pressure, passing through a 2-4 mm sieve; Fluidized bed drying: until moisture content ≤5%, then UV sterilize for 30 minutes.

[0036] Furthermore, the preparation method of the liquid dosage form may include: compounding PHA nanoemulsion (particle size ≤500nm) with potassium phosphite aqueous solution, adding 0.3% xanthan gum for thickening, and adjusting the pH to 6.0-7.0.

[0037] Furthermore, the granule dosage form can be prepared using an extrusion granulation process, with a particle size of 2-4 mm, a disintegration time of ≤15 minutes, and a moisture content of ≤5%.

[0038] The present invention also provides the use of the above composition in the preparation of fertilizers, crop antibacterial agents and / or soil conditioners.

[0039] Furthermore, regarding the application of the composition of this invention, it is recommended to use basal application (mixed with organic fertilizer) or fertigation / drip irrigation. These two methods allow the fertilizer-pesticide composition to be distributed more evenly in the soil, improving its utilization efficiency.

[0040] Application methods include: Basal application / broadcast application: The powder is mixed with organic fertilizer as a basal fertilizer to improve soil aggregate structure and increase nutrient utilization.

[0041] Foliar spraying: Spray with a 1000-2000 times diluted solution of the powder to enhance the crop's resistance to late blight and Phytophthora blight.

[0042] The present invention also provides the use of the above composition in any of the following aspects: (1) Promote crop growth, increase crop yield and / or quality; (2) Improve the soil environment and / or enhance soil fertility; (3) Improve crop antibacterial properties; (4) Increase crop plant height, aboveground fresh weight, underground fresh weight, fruit transverse diameter, fruit longitudinal diameter and / or single fruit fresh weight; (5) Increase the organic matter and / or phosphorus content of the soil; (6) Reduce the EC value of the soil.

[0043] In the application of this invention, the crop is tomato, cucumber, pepper, lettuce, watermelon, eggplant, strawberry, or grape; And / or, the bacteria is late blight pathogen.

[0044] The present invention also provides a product comprising the above-described composition; the product is a fertilizer, a crop antibacterial agent, or a soil conditioner.

[0045] The beneficial effects of this invention are at least as follows: This invention provides a novel composition with superior antibacterial properties, enhancing crop disease resistance and yield, and exhibiting better antibacterial effects than potassium phosphate alone. Furthermore, the composition of this invention can activate fixed phosphorus in the soil, increasing phosphorus content and soil organic matter content, reducing soil electrical conductivity (EC), improving the soil's ecological environment, and comprehensively achieving increased crop yield. Detailed Implementation

[0046] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0047] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available or prepared according to conventional methods in the art.

[0048] In the specific embodiments of this invention, the potassium phosphite used in the examples is potassium dihydrogen phosphite with a purity of 98% (powder), CAS: 13977-65-6, purchased from Wuhan Jiyesheng Chemical Co., Ltd.; PHA is PHBH powder, from Shanghai Lanjing Microbial Technology Co., Ltd., with a weight-average molecular weight of 600,000 to 800,000 Da, brand name BP330, purity of 80%, and particle size range of 0.5 μm to 180 μm.

[0049] Example 1: Preparation of a synergistic fertilizer composition This embodiment describes the preparation of a fertilizer composition with a total weight of 1 kg. PHA and potassium phosphite are mixed evenly with the fertilizer carrier according to the weight percentage, and compositions with different PHA + potassium phosphite ratios are prepared according to Table 1 below.

[0050] Table 1 Example 2: Effects of different formulations in Table 1 on the control efficacy against tomato late blight. Test method: Experimental Design: Eight treatment groups were set up: blank control (CK, treated with water), experimental group 1 (treated with potassium phosphite alone), experimental group 2 (treated with PHA alone), and experimental groups 3-7 (PHA to potassium phosphite mass ratios of 1:0.2, 1:0.4, 1:0.8, 1:1, and 1:2, respectively). Each treatment was replicated three times. A pot experiment was conducted, with one tomato planted in each pot. The tomato variety was "Zhongshu No. 5". After transplanting the tomatoes, 30 mg of the sample from each treatment (see Table 1) was diluted in 200 ml of water and then applied to the soil.

[0051] Inoculation and Management: When tomato seedlings have 3-4 true leaves, inoculate them with late blight pathogen (… Phytophthora infestans ) Spore suspension (concentration of 1×10 5 100 mL (infected cells / mL), maintain air humidity above 90% and temperature 20-25℃ after inoculation.

[0052] Investigation and statistics: On the 14th day after inoculation, the disease index of tomato plants in each treatment group was investigated, and the control effect was calculated. The results are shown in Table 2.

[0053] Disease index calculation method: 0 = No lesions; 1 = Lesion area less than 10% of leaf area; 3 = Lesion area 11%-25% of leaf area; 5 = Lesion area 26%-40% of leaf area; 7 = Lesion area 41%-60% of leaf area; 9 = Lesion area more than 60% of leaf area (excluding 60%).

[0054] Disease index = ∑(number of diseased leaves at each level × representative value at each level) / total number of leaves surveyed × highest representative value × 100.

[0055] Prevention and control effect (%) = (CK disease index - treatment disease index) / CK disease index × 100%.

[0056] Table 2 Results analysis: The treatment with a ratio of PHA to potassium phosphite of 1:0.8 showed the best control effect, with a 26.9% improvement compared to potassium phosphite alone.

[0057] Example 3: Effects of different ratios of the compositions in Table 1 on cucumber growth and soil EC value Test method: Experimental materials: cucumber variety "Jinyou 35" and soil was saline soil (EC value 4.2 mS / cm).

[0058] Experimental design: Eight treatment groups were set up: blank control (CK, treated with water), experimental group 1 (treated with potassium phosphite alone), experimental group 2 (treated with PHA alone), and experimental groups 3-7 (PHA to potassium phosphite mass ratios of 1:0.2, 1:0.4, 1:0.8, 1:1, and 1:2, respectively). Each treatment was replicated four times, and a pot experiment was conducted with two cucumber plants per pot.

[0059] Fertilization and management: After transplanting cucumber seedlings, apply the fertilizer-pesticide mixture every 7 days for a total of 3 applications. The application rate is 200 mL per pot, with each 500 mL containing 30 mg of the sample (see Table 1). The control group was watered with plain water.

[0060] Measurement items: Five days after the third irrigation, the plant height, aboveground fresh weight, and underground fresh weight of cucumber plants were measured. After harvest, the soil organic matter, EC value, and phosphorus content were measured. The results are shown in Table 3.

[0061] Table 3 Results analysis: The experimental group 5 (1:0.8 treatment group) showed the greatest increase in plant height and fresh weight, a 42.9% decrease in soil EC value compared to the control group, a 37.3% increase in organic matter, and a 59.8% increase in available phosphorus content, which were significantly better than the groups treated with PHA alone, potassium phosphite, and other treatments.

[0062] Example 4: Effects of different formulations in Table 1 on the prevention and control of root rot in lettuce and their biomass influence. Test method: Experimental materials: The lettuce variety was "Colorful No. 2", and the tested pathogen was *Bacterium tumefaciens*, the root rot pathogen of lettuce. Fusarium solani ).

[0063] Experimental design: The treatment groups were set up as in Example 3, with each treatment replicated 4 times. The experiment was conducted in pots, with 5 plants per pot. After sowing, 30 mg of the sample (see Table 1) was diluted to 200 mL and applied to the soil every 7 days for a total of 3 times.

[0064] Inoculation and investigation: During the seedling stage (2 true leaves), irrigate with a suspension of root rot fungal spores (1×10⁻⁶). 5 (Inoculation / mL), 100mL per pot. Disease index was assessed 14 days post-inoculation (grading criteria: Grade 0 no rot, Grade 1 root rot <1 / 4, Grade 3 1 / 4-1 / 2, Grade 5 >1 / 2), and disease index and control effect were calculated. Fresh weight of aboveground and underground parts was measured at harvest. Results are shown in Table 4.

[0065] Disease index = ∑(number of disease roots at each level × representative value at each level) / total number of disease roots surveyed × highest level representative value × 100.

[0066] Prevention and control effect (%) = (CK disease index - treatment disease index) / CK disease index × 100%.

[0067] Table 4 Results analysis: Experimental group 5 (1:0.8) showed a 72.1% control effect on root rot, with the fresh weight of the aboveground and underground parts increasing by 106.5% and 152.4% respectively compared to the control (CK). This indicates that the ratio can effectively inhibit root diseases, promote root development and plant biomass accumulation, and has a significant effect on fibrous root crops.

[0068] Example 5: Effects of different ratios of the compositions in Table 1 on watermelon fruit enlargement Test method: Experimental materials: Watermelon, variety "Jingxin No. 1", soil is sandy loam with medium fertility.

[0069] Experimental Design: A blank control (CK, treated with water) was established, along with experimental group 1 (potassium phosphite alone), experimental group 2 (phosphite alone), and experimental groups 3-7 (phosphite to potassium phosphite mass ratios of 1:0.2, 1:0.4, 1:0.8, 1:1, and 1:2). Each treatment was replicated three times. The plants were grown in open fields, and the application rate for each treatment composition (see Table 1) was 1 kg / mu. Approximately 0.5 mu of land was allocated to each treatment, and the application was given once each during the seedling, fruit setting, and fruit expansion stages (prepared as a water solution for irrigation).

[0070] Measurement items: When watermelons are ripe and harvested, measure the transverse diameter, longitudinal diameter, and fresh weight of the fruit.

[0071] The results are shown in Table 5.

[0072] Table 5 Results analysis: The experimental group 5 (1:0.8) showed the largest transverse diameter, longitudinal diameter, and fresh weight of watermelon fruits, increasing by 47.3%, 43.9%, and 84.4% respectively compared to the control (CK); by 24.7%, 23.9%, and 43.9% respectively compared to experimental group 1; and by 32.0%, 30.5%, and 55.3% respectively compared to experimental group 2. This indicates that this ratio significantly promotes watermelon fruit enlargement and increases the weight of individual fruits, with a far superior promoting effect compared to potassium phosphate alone, PHA alone, or other combinations, demonstrating an excellent synergistic effect on watermelon fruit enlargement.

[0073] Example 6: Suitability test of PHA and potassium phosphite composition on different crops Test method: Experimental materials: Tomato (Zhongshu No. 5), cucumber (Jinyou No. 35), pepper (Zhongjiao No. 105), lettuce (Binfen No. 2), eggplant (Huazi No. 6), strawberry (Hongyan No. 99) and grape (Xiahei).

[0074] Experimental design: For each crop, a blank control (CK, treated with water), experimental group 1 (potassium phosphite alone, see Table 1 for details), and experimental group 5 (PHA to potassium phosphite mass ratio of 1:0.8, see Table 1 for details) were set up. Open field cultivation was adopted.

[0075] Fertilization and management: The management measures were the same for all treatments. The amount of fertilizer used for each treatment sample was 1 kg per mu, applied 3 times, at the seedling stage, flowering stage and fruiting stage, and applied by irrigation.

[0076] Inoculation: When the seedlings of each crop have grown 3-4 true leaves, inoculate them with the pathogen Botrytis cinerea (…). Botrytis cinerea ) Spore suspension (1×10 5 (100 mL per plant), 100 mL per plant.

[0077] Test items: Disease resistance was tested 14 days after inoculation (see Example 2 for specific methods). Yields of each crop were measured after harvest. Results are shown in Table 6.

[0078] Table 6 Results analysis: The experimental results show that the compound composition of PHA and potassium phosphite has good applicability and significant yield-increasing and disease-resistant effects on a variety of crops. The yield increase rate and control efficacy vary among different crops, which may be related to factors such as crop type, growth habits, and sensitivity to pesticides and fertilizers. However, overall, the compound composition is significantly more effective than potassium phosphite alone or the blank control, indicating that this composition has broad application prospects.

[0079] in conclusion The fertilizer-pesticide composition containing PHA and potassium phosphite provided by this invention achieves a synergistic effect of PHA and potassium phosphite through a rational formulation design. Experimental data shows that this composition can significantly improve crop disease resistance, promote crop growth, increase crop yield and quality, and simultaneously improve the soil environment and enhance soil fertility. This composition has advantages such as scientific formulation, simple preparation, convenient use, and significant effects, making it suitable for various crops and different soil conditions, and possessing broad application prospects and market value.

[0080] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A composition, characterized in that, include: PHA and potassium phosphite; the mass ratio of PHA to potassium phosphite is 1:(0.2-1.25).

2. The composition according to claim 1, characterized in that, The mass ratio of PHA to potassium phosphite is 1:(0.4-1).

3. The composition according to claim 2, characterized in that, The mass ratio of PHA to potassium phosphite is 1:(0.8-0.82).

4. The composition according to any one of claims 1-3, characterized in that, It also includes a carrier, preferably glucose powder.

5. The composition according to any one of claims 1-4, characterized in that, The PHA contains structural units represented by the following general formula I: [CHR1(CH2)x COO] General Formula I; Wherein, R1 is a straight-chain or branched alkyl group represented by CpH2p+1, p is an integer from 1 to 15, preferably an integer from 1 to 10, more preferably an integer from 1 to 8; R1 is preferably methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, pentyl or hexyl; x is 1, 2 or 3; Preferably, the PHA is PHBH and the potassium phosphite is potassium dihydrogen phosphite.

6. A method for preparing the composition according to any one of claims 1-5, characterized in that, This includes the step of thoroughly mixing PHA and potassium phosphite.

7. Use of the composition according to any one of claims 1-5 in the preparation of fertilizers, crop antibacterial agents and / or soil conditioners.

8. The use of the composition according to any one of claims 1-5 in any of the following aspects: (1) Promote crop growth, increase crop yield and / or quality; (2) Improve the soil environment and / or enhance soil fertility; (3) Improve crop antibacterial properties; (4) Increase crop plant height, aboveground fresh weight, underground fresh weight, fruit transverse diameter, fruit longitudinal diameter and / or single fruit fresh weight; (5) Increase the organic matter and / or phosphorus content of the soil; (6) Reduce the EC value of the soil.

9. The application according to claim 8, characterized in that, The crops mentioned are tomatoes, cucumbers, peppers, lettuce, watermelons, eggplants, strawberries, or grapes; And / or, the bacteria is late blight pathogen.

10. A product characterized in that, The product comprises the composition according to any one of claims 1-5; the product is a fertilizer, crop antibacterial agent, or soil conditioner.

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