Efficient phosphate-solubilizing bacteria and application thereof

Abstract

The invention relates to an efficient phosphate-solubilizing bacterium, and the preservation number of the efficient phosphate-solubilizing bacterium is GDMCC No: 65495. The efficient phosphate solubilizing bacteria X32 not only has good phosphate solubilizing capacity, but also promotes plant growth by adjusting the content of chlorophyll b and the content of various enzymes of seedlings. Meanwhile, the strain X32 also has the capability of producing siderophores and indoleacetic acid, so that the strain X32 has the effects of improving soil performance and promoting plant growth. When the strain absorbs phosphorus in soil, insoluble phosphorus in the soil can be dissolved, so that the utilization of the phosphorus in the soil by plants can be improved. Meanwhile, the mixed fertilizer containing the phosphate solubilizing bacteria can reduce the usage amount of a phosphate fertilizer, improve the utilization rate of the phosphate fertilizer, promote soil phosphorus circulation, improve soil fertility and reduce the agricultural cost, and the bacterial strain capable of producing siderophores and producing indoleacetic acid has the effects of promoting plant growth and enhancing the surface area and length of a plant root system; the absorption of crops on soil nutrients is enhanced.

Description

Technical Field

[0001] The invention relates to a highly efficient phosphate-dissolving bacterium and application thereof, belonging to the technical field of bioengineering. Background Art

[0002] Phosphorus is the second most essential element for plant growth, second only to nitrogen, and is essential for plant growth, development and metabolism. Lack of phosphorus will lead to a decrease in crop yield and quality, and phosphorus can also improve plant stress resistance, helping to resist drought and cold. With the growth of demand for crops, the use of phosphate fertilizers is also increasing to cope with the problem of soil phosphorus deficiency. However, phosphate fertilizers are mainly derived from phosphate ore, the formation of which takes hundreds of years and is irreversible. Although my country's soil is rich in phosphate resources, due to the low average grade of phosphate ore, the treatment of low-grade phosphate ore will not only lead to serious chemical pollution, but also increase economic costs. In addition, the utilization rate of phosphate fertilizers is less than 30%, and excessive use of phosphate fertilizers will cause harm to the environment, such as increasing soil acidity, causing soil caking, and may promote the combination of soil and heavy metals, producing harmful byproducts to pollute the soil.

[0003] Biofertilizers, as a low-cost, effective and renewable source of plant nutrients, can be used as a supplement to chemical fertilizers. Microorganisms in biofertilizers can enhance the activity of plant roots in the soil, and among the many factors that affect the available phosphorus content in the soil, microorganisms are particularly important for promoting soil phosphorus cycling. Phosphate-solubilizing microorganisms (PSBs) can decompose poorly soluble inorganic phosphorus compounds and organic phosphorus compounds that cannot be absorbed and utilized by plants into water-soluble phosphorus that is easily absorbed by plants by secreting organic acids and phosphatases. Therefore, the efficient phosphate-solubilizing bacteria studied in the present invention are efficient heat-resistant phosphate-solubilizing microorganisms that can thrive under common environmental conditions. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a highly efficient phosphate-dissolving bacteria, and an application and screening method of the highly efficient phosphate-dissolving bacteria.

[0005] A technical solution proposed by the present invention to solve the above-mentioned technical problems is: a highly efficient phosphate-dissolving bacteria, named Bacillus subtilis X32, was deposited in Guangdong Provincial Microbiological Culture Collection Center (Guangdong, China) on November 18, 2024, abbreviated as GDMCC, and the preservation number is No: 65495.

[0006] The above-mentioned method for cultivating highly efficient phosphate-dissolving bacteria comprises the following specific steps:

[0007] A. Mix the soil samples evenly, take 5g of the sample from the mixed soil to make a soil suspension, and place the soil suspension in a constant temperature shaking water bath at 80℃ and 180r / min for 15min. Then dilute the soil suspension into a gradient dilution using the ten-fold dilution separation method, and spread 100μL of the dilution on the LB medium plate; finally, pick out the single colony on the LB medium and purify it for 2~3 generations by the plate streak method, then inoculate the purified colony on the slant medium and store it at 4℃ to obtain the screened strain;

[0008] B. Inoculate the selected strains onto inorganic phosphorus culture medium and culture for 7 days. Colonies with clear transparent circles are highly efficient phosphate-dissolving bacteria.

[0009] The above soil samples were collected from navel orange orchards in Xinfeng County, Ganzhou City (25°14'43”N, 114°58'13”E) and Gan County (25°48'82”N, 115°09'99”E). Fruit trees with high yields in previous years were selected, and the soil was dug 10-30 cm below the drip line of the navel orange trees to collect the soil near the navel orange rootlets. The soil was placed in a sterile sealed bag together with the rootlets and brought back to the laboratory for storage in a 4°C refrigerator for later use.

[0010] A technical solution proposed by the present invention to solve the above technical problem is: application of the above efficient phosphate-dissolving bacteria in promoting plant growth.

[0011] A technical solution proposed by the present invention to solve the above technical problems is: application of the above efficient phosphate-dissolving bacteria in producing iron carriers and indoleacetic acid.

[0012] A technical solution proposed by the present invention to solve the above technical problem is: application of the above high-efficiency phosphate-dissolving bacteria in promoting the growth of navel orange seedlings.

[0013] A technical solution proposed by the present invention to solve the above technical problem is: application of the above high-efficiency phosphate-dissolving bacteria in reducing the chlorophyll b content of navel orange seedlings.

[0014] A technical solution proposed by the present invention to solve the above technical problems is: a fertilizer containing the above efficient phosphate-dissolving bacteria.

[0015] A technical solution proposed by the present invention to solve the above technical problems is: a soil conditioner containing the high-efficiency phosphate-dissolving bacteria as described in claim 1.

[0016] The present invention has positive effects:

[0017] The efficient phosphate-dissolving bacteria X32 of the present invention not only has good phosphate-dissolving ability, but also promotes plant growth by regulating the chlorophyll b content and the various enzyme contents of the seedlings. At the same time, the strain X32 also has the ability to produce siderophores and indoleacetic acid, and these characteristics enable it to improve soil performance and promote plant growth. When the strain absorbs soil phosphorus, it will dissolve the insoluble phosphorus in the soil, which can improve the utilization of soil phosphorus by plants. At the same time, the mixed fertilizer containing phosphate-dissolving bacteria can reduce the use amount of phosphate fertilizer, improve the utilization rate of phosphate fertilizer, promote soil phosphorus circulation, improve soil fertility, and reduce agricultural costs at the same time. The strain with the ability to produce siderophores and indoleacetic acid has the effect of promoting plant growth and enhancing the surface area and length of the plant root system, and enhances the absorption of soil nutrients by crops. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a phylogenetic tree constructed based on the homology of the housekeeping gene sequences of strain X32;

[0019] Figure 2 is the phosphorus standard curve;

[0020] Figure 3 It is the phosphate solubilizing effect of phosphate solubilizing bacteria under different pH conditions;

[0021] Figure 4 Effect of inoculum size on phosphate solubilization of strain X32;

[0022] Figure 5 The effect of different carbon sources on the phosphorus solubilization of strain X32;

[0023] Figure 6 The effect of different nitrogen sources on the phosphorus solubilization of strain X32;

[0024] Figure 7 The effect of different phosphorus sources on the phosphorus solubilization of strain X32;

[0025] Figure 8 is the genomic circle of strain X32;

[0026] Fig. 9 This is the KEGG signaling pathway functional annotation result of strain X32;

[0027] Fig.10 It is the change of growth parameters of potted plants;

[0028] Fig.11 It is the change of enzyme content in potted leaves;

[0029] Fig.12 It is the changes in the chlorophyll and carotenoid content of potted leaves. DETAILED DESCRIPTION Example

[0030] 1. Cultivation method of efficient phosphate-dissolving bacteria.

[0031] The cultivation method of efficient phosphate-dissolving bacteria of this embodiment comprises the following specific steps:

[0032] A. Mix the soil samples evenly, take 5g of the sample from the mixed soil to make a soil suspension, and place the soil suspension in a constant temperature shaking water bath at 80℃ and 180r / min for 15min. Then separate the soil suspension (dilution factor is 10 6 ); then take 100 μL and spread it on E. coli culture medium; finally, pick out the single colony on E. coli and purify it for 2 generations by plate streaking method, then inoculate the purified colony on slant culture medium and store it at 4°C to obtain the screened strain;

[0033] B. Inoculate the selected strains onto inorganic phosphorus culture medium and culture for 7 days. Colonies with clear transparent circles are highly efficient phosphate-dissolving bacteria.

[0034] The soil samples of this embodiment were collected from navel orange orchards in Xinfeng County, Ganzhou City (25°14'43" N, 114°58'13" E) and Gan County (25°48'82" N, 115°09'99" E). Fruit trees with high yields in previous years were selected, and the soil was dug 10-30 cm below the drip line of the navel orange tree to collect the soil near the navel orange fibrous roots. The soil was put into a sterile sealed bag together with the fibrous roots and brought back to the laboratory for storage in a refrigerator at 4°C for later use.

[0035] The Bacillus subtilis X32 obtained by the above-mentioned culture method was deposited in the Guangdong Provincial Microbiological Culture Collection Center on November 18, 2024, with the deposit number GDMCC No: 65495.

[0036] 2. Identification of strains.

[0037] The microbial strains with phosphate solubilizing ability isolated from the rhizosphere of navel orange in southern Jiangxi were inoculated on LB solid medium to observe their morphological characteristics. Their surface was rough and slightly yellow. Their physiological and biochemical properties are shown in Table 1. The strain DNA was extracted for PCR amplification. After comparison, the results showed that the strain had the highest similarity with Bacillus spizizenii, reaching 99.4%, but strain X32 also had a high similarity with other Bacillus (99.4%-92.0%), and the similarity with Bacillus tequilensis also reached 99.1%. The similarities with Bacillus vallismortis, Bacillus halotolerans and Bacillus sp010093085 were 98.7%, 98.6% and 98.4% respectively, and the similarity between strain X32 and Bacillus safensis also reached 92.0%, which indicated that strain X32 belonged to the Bacillus group, and the use of housekeeping genes could help classify bacterial genera and species.

[0038] Table 1 Physiological and biochemical properties of strain X32 Table 1 Physiological and Biochemical Characterization of Strain X32

[0039] 3. Phosphate solubilization ability of strain X32.

[0040] After preliminary screening, it was determined that the strain had the ability to solubilize phosphate. Figure 2 The phosphorus standard curve (y=0.2291x+0.0583) calculated that the phosphorus solubilizing capacity of X32 reached 111.8 mg / L.

[0041] 4. Single factor determination.

[0042] 1. pH In inorganic phosphorus culture media under different pH conditions, by measuring the effective phosphorus content in blank culture media without bacteria and inoculated bacteria, it was found that the effective phosphorus content of both was the highest at pH = 5. The data showed that compared with the blank group, the effective phosphorus content of the experimental group was lower than that of the blank group at pH = 5, which indicates that bacteria did not dephosphate at pH = 5. Figure 3 The phosphate-solubilizing effect of phosphate-solubilizing bacteria under different pH conditions showed that the strain showed obvious phosphate-solubilizing effect when pH>5, and the phosphate-solubilizing effect was best when pH=7.

[0043] 2. Inoculation volume Different inoculum amounts will result in different phosphate dissolution effects. Figure 4 The effect of inoculum size on the phosphate solubilization effect of strain X32 found that there was no significant difference in phosphate solubilization when the inoculum size was between 1% and 3%. When the inoculum size varied between 0.5% and 3%, statistical analysis showed that the difference in phosphate solubilization was not significant (P>0.05). However, when the inoculum size exceeded 3%, the phosphate solubilization ability of strain X32 decreased significantly, showing significant differences compared with other inoculum levels (P<0.05). Specifically, at an inoculum size of 3%, the strain had the highest phosphate solubility, with an available phosphorus content of 123.63 mg / L. These results indicate that there is an optimal inoculum size for strain X32 to achieve maximum phosphate solubilization. Beyond this optimal point, an increase in the inoculum size can lead to resource competition or changes in the microenvironment, which can have a negative impact on the solubilization activity of the strain.

[0044] 3. Effects of different carbon sources on phosphate-solubilizing bacteria pass Figure 5 The effect of different carbon sources on the phosphorus solubilization effect of strain X32 found that different carbon sources had different effects on the ability of the strain to dissolve tricalcium phosphate. The order of effective phosphorus content in the solution was mannitol>sucrose>glucose>fructose>galactose>lactose. Among them, when the strain used mannitol as the carbon source, the effective phosphorus content of the solution was 118.95 mg / L, which was 100.47 mg / L higher than that of the blank group. When sucrose, glucose, and fructose were used as carbon sources, the difference in the phosphorus solubilization ability of tricalcium phosphate was not large. However, when lactose was used as the carbon source, it was found that the effective phosphorus content of the culture medium with lactose as the carbon source was lower than that of the blank experimental group, which shows that the strain cannot use lactose as a carbon source to improve its phosphorus solubilization ability.

[0045] 4. Effects of different phosphorus sources on phosphate-solubilizing bacteria pass Figure 6 The effect of different phosphorus sources on the phosphorus solubilization effect of strain X32 found that the strain had different phosphorus solubilization abilities for different phosphorus sources. Under the same carbon and nitrogen source conditions, the phosphorus solubilization effect of the strain on tricalcium phosphate, calcium hydrogen phosphate, iron sulfate and aluminum phosphate was explored, and the effective phosphorus content in the solution was calcium hydrogen phosphate> tricalcium phosphate> iron phosphate> aluminum phosphate. Among them, the strain had the best phosphorus solubilization effect on calcium hydrogen phosphate, and the effective phosphorus content of the solution was 208.82 mg / L, which was 134.59 mg / L higher than that of the blank group. When tricalcium phosphate was used as the carbon source, the effective phosphorus content of the solution was 112.47 mg / L, which was 103.57 mg / L higher than that of the blank group. However, when iron phosphate and aluminum phosphate were used as the phosphorus sources, it was found that the effective phosphorus content of the culture medium with iron phosphate and aluminum phosphate as the phosphorus source was lower than that of the blank experimental group, which indicates that the strain cannot convert iron phosphate and aluminum phosphate into soluble phosphorus.

[0046] Whole genome sequencing results The whole genome sequence characteristics of Bacillus subtilis subsp. Steinernema X32 are summarized in Table 2. The genome size is 4,688,635 bp, and the content is calculated to be 43.41%. They contain 4224 protein coding genes (CDS), 85 tRNAs, 10 rRNAs, and 100 sRNAs, as shown in Table 3. The genome circle diagram of strain X32 is shown in Figure 8 As shown. The first and fourth circles of the circle diagram from the outside to the inside are CDS on the positive and negative chains, and different colors represent different COG functional classifications; the second and third circles are CDS, tRNA, and rRNA on the positive and negative chains, respectively; the fifth circle is the GC content, and the outward part indicates that the GC content of the region is higher than the average GC content of the whole genome. The higher the peak value, the greater the difference from the average GC content; the inward part indicates that the GC content of the region is lower than the average GC content of the whole genome. The higher the peak value, the greater the difference from the average GC content; the sixth circle is the GC-Skew value, and the specific algorithm is GC / G+C, which can assist in judging the leading chain and the lagging chain. Generally, the leading chain GC skew>0, and the lagging chain GC skew<0. It can also assist in judging the replication start point (minimum cumulative offset) and end point (maximum cumulative offset), which is especially important for circular genomes; the innermost circle is the genome size marker. CRISPR-Cas analysis showed that strain X32 contained 2 CRISPRs with lengths of 112bp and 105bp respectively; genomic island analysis showed that X32 contained 6 predicted genomic islands with lengths ranging from 19622bp, 16433bp, 134126bp, 8144bp, 5882bp, and 31197bp respectively.

[0047] Table 2 Summary of the whole genome sequence characteristics of strain X32 Table 2 Summary of Whole Genome Sequence Features of Strain X32

[0048] Table 3 Summary of phosphate-solubilizing genes related to phosphate-solubilizing ability of strain X32 Table 3 summarizes the phosphorus-solubilizing genes associated with the phosphorus-solubilizing ability of strain X32.

[0049] By comparison, it was found that strain X32 has 20 genes related to phosphorus activation. The strain contains 7 phosphate mineralization genes, including glpA, glpQ, glpK, phoA, phoD and other genes. Studies have shown that the proteins encoded by the glp genes are involved in regulating the absorption and transport of phosphorus in the soil by plants. Strains expressing the glp genes can more effectively utilize phosphorus resources in the environment, improve their bioavailability, and thus promote the phosphorus absorption efficiency of host plants. The pho gene usually encodes proteins that regulate phosphorus metabolism. These genes and proteins play a role in phosphorus absorption and transport and phosphorus metabolism in bacteria. Some proteins encoded by the pho gene are also involved in regulating phosphorus signal transduction pathways in bacteria, helping bacteria to sense changes in phosphorus concentration in the external environment and make adaptive responses, such as secreting phosphatases and organic acids, and increasing the expression of phosphorus transport proteins. These biochemical processes help release fixed phosphorus in the soil and convert it into a form that can be absorbed by plants.

[0050] Secondly, strain X32 has 7 genes related to phosphonate transport and 1 phosphonate mineralization, including glpT, glpP, pstA, pstB, pstC, pstS and other genes, and the transport and mineralization of phosphonates involve the absorption and utilization of organophosphorus compounds by bacteria. Organophosphorus compounds are an important source of phosphorus, including phosphonates and organophosphates. Bacteria need phosphonate transport systems to effectively absorb and utilize these organophosphorus compounds as a source of phosphorus for growth and metabolism. Phosphorus deficiency response regulatory genes can help bacteria cope with the lack of phosphorus in the external environment. At the same time, phosphorus deficiency response regulatory genes can help bacteria adjust phosphorus metabolic pathways under phosphorus deficiency conditions, and synthesize specific phosphorus metabolic enzymes or regulate the activity of phosphorus metabolic pathways to adapt to phosphorus limitation conditions.

[0051] In summary, the potential role of genes such as glp, pho and pst in the interaction between microorganisms and plants not only provides a new perspective for understanding phosphorus cycling, but also opens the way for the development of new agricultural technologies based on microorganisms. By screening and utilizing beneficial microorganisms containing these key genes, crop yields can be effectively increased, fertilizer use can be reduced, and agricultural sustainable development can be achieved.

[0052] 6. Potted plant experiment.

[0053] 1. In the pot experiment, the growth parameters of citrus seedlings were monitored to evaluate the effects of the treatments on their development. Growth parameters such as plant height, fresh weight of aboveground parts, fresh weight of underground parts, dry weight of aboveground parts and dry weight of underground parts were recorded. Fig. 9As shown, citrus seedlings treated with strain X32 showed significant improvements in these growth parameters compared to the control group. This indicates that strain X32 has a positive effect on the overall growth and development of citrus seedlings. The observed enhancement in growth parameters suggests that strain X32 helps the plants to better absorb and utilize nutrients. The increase in plant height and biomass (fresh and dry weight) can be attributed to the strain's ability to solubilize phosphorus and potentially other nutrients, thereby improving the nutritional status of the seedlings. In addition, the positive effects on above- and below-ground biomass suggest that strain X32 not only promotes shoot growth but also promotes root development, which is essential for plant establishment and long-term health.

[0054] 2. Changes in enzyme content in leaves of navel orange seedlings, measuring key enzymes involved in plant metabolism, such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Fig.10 As shown, leaf enzyme activities in seedlings treated with strain X32 showed significant increases compared to the control group. The increase in enzyme activity suggests that strain X32 enhances the plant's antioxidant defense system, contributing to improved stress resistance and overall health of citrus seedlings. Increased levels of SOD, CAT, and POD indicate an enhanced ability to scavenge reactive oxygen species (ROS). These enzymes play a key role in protecting cells from oxidative damage caused by environmental stress. By increasing the activity of these enzymes, strain X32 appears to enhance the plant's natural defenses, thereby promoting better growth and resilience.

[0055] 3. Changes in chlorophyll and carotenoids in navel orange leaves, through Fig.11 As shown in the results, strain X32 had no significant effect on the chlorophyll a content and carotenoid content in the leaves of seedlings. However, the strain had a significant effect on the chlorophyll b content and total chlorophyll content of the inoculated seedlings. This finding suggests that strain X32 affects the photosynthetic efficiency of navel orange seedlings by regulating the level of chlorophyll b. Although the total chlorophyll content did not increase significantly overall, the decrease in chlorophyll b content suggests that strain X32 adjusted the proportion of photosynthetic pigments under specific conditions, thereby affecting the physiological functions of the plant. In addition, since the carotenoid content remained stable, this suggests that strain X32 had no significant effect on the antioxidant capacity and photoprotection mechanism of the seedlings.

[0056] The present invention screens out a strain with efficient phosphate solubilization ability from rhizosphere soil of navel orange in southern Jiangxi. It is found through measurement that the strain not only has certain ability to produce indoleacetic acid and siderophore. Moreover, under the condition of pH 5, the effective phosphorus content in the culture medium inoculated with the strain is lower than that in the blank group. This is because the solubility of tricalcium phosphate is higher under acidic conditions in inorganic phosphorus culture medium, which leads to sufficient effective phosphorus content in the culture medium. In this case, phosphate solubilizing bacteria will reduce its phosphate solubilization activity. Although pH has a certain influence on the phosphate solubilization effect of the strain, it is not a decisive factor in the application of microorganisms. In the study of the biocontrol effect of endophytic bacillus amyloliquefaciens QC-Y on citrus canker, it is found that pH has no obvious influence on it, and the activity difference is not obvious in an environment with pH 4 and in an environment with pH 10.

[0057] In addition, the strain's phosphorus solubilization effect under different carbon sources, nitrogen sources and phosphorus sources. The experimental results show that when mannitol is used as the carbon source, the strain has the best phosphorus solubilization effect; in terms of nitrogen source and phosphorus source, the phosphorus solubilization effect is most obvious when ammonium sulfate and calcium bisulfate are used respectively. In fact, studies have shown that the ability of phosphorus-solubilizing microorganisms to convert insoluble organic phosphorus and inorganic phosphorus is related to the richness of soil nutrients. Among them, carbon source and nitrogen source are the main nutrients for microorganisms. Supplying different carbon sources and nitrogen sources will affect the metabolic activities of microorganisms, and then affect their phosphorus solubilization effect. Similarly, different phosphorus sources also affect the phosphorus solubilization effect of microorganisms. For example, when Micromonospora nigra SY7 was cultured, it was found that it had the best phosphorus solubilization effect when Ca3(PO4)2 was used as the phosphorus source.

[0058] Further studies showed that the strain was genetically identified as Bacillus_spizizenii. At the whole genome level, the strain was found to contain inorganic phosphorus solubilization-related genes (such as gdh and gltA), as well as phosphorus transport-related genes (such as glpT, glpP, pstA, pstB, pstC and pstS). In addition, the strain also carried phosphate mineralization-related genes (such as glpQ, glpA, glpK, phoA, phoD, phnO and phytase genes) and phosphorus deficiency response regulatory genes (such as phoR). The presence of these genes provides a theoretical basis for the application of the strain in biofertilizers and helps to further understand the feasibility of its practical application.

[0059] Chlorophyll plays a vital role in the light absorption process of photosynthesis, while carotenoids determine the intensity of photosynthesis. Effects of strain X32 on the chlorophyll and carotenoid content of navel orange seedlings. According to the data, strain X32 had no significant effect on the chlorophyll a content and carotenoid content of seedling leaves, but had a significant effect on the chlorophyll b content and total chlorophyll content. This suggests that strain X32 affects the photosynthetic efficiency of navel orange seedlings by regulating the level of chlorophyll b. Although the total chlorophyll content did not increase significantly, the reduction in chlorophyll b means that strain X32 adjusted the proportion of photosynthetic pigments under specific conditions, thereby affecting the physiological state of the plant. In addition, since the carotenoid content remained unchanged, this suggests that strain X32 had no significant effect on the antioxidant capacity and photoprotection mechanism of the seedlings. Studies have shown that phosphate-solubilizing bacteria can promote the absorption of phosphorus by plants to enhance the photosynthetic rate of plants.

[0060] The present invention found that the contents of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the navel orange seedlings of the experimental group were significantly improved, and there was a significant difference compared with the blank group (P<0.05). This shows that the inoculation of growth-promoting bacteria can increase the activity of SOD, CAT and POD enzymes in plants. In some studies, it can be understood that the role of SOD, CAT and POD enzymes is to remove reactive oxygen (ROS) to reduce its damage to plants. In existing studies, it was found that the inoculation of agglomerative mycorrhizal fungi (AFM) increased the activity of CAT and SOD in plants, which also showed that the inoculation of beneficial microorganisms can improve the defense ability of plants.

[0061] The strain X32 of the present invention not only has good phosphate solubilizing ability, but also promotes plant growth by regulating the chlorophyll b content and the various enzyme contents of the seedlings. At the same time, the strain X32 also has the ability to produce siderophores and indoleacetic acid, and these characteristics enable it to improve soil performance and promote plant growth. When the strain absorbs soil phosphorus, it will dissolve the insoluble phosphorus in the soil, which can improve the utilization of soil phosphorus by plants. At the same time, mixed fertilizers containing phosphate-solubilizing bacteria can reduce the amount of phosphate fertilizer used, improve the utilization rate of phosphate fertilizer, promote soil phosphorus circulation, and improve soil fertility. At the same time, this has a good effect on reducing agricultural costs. The strain with the ability to produce siderophores and indoleacetic acid has the effect of promoting plant growth and enhancing the surface area and length of the plant root system. This can enhance the absorption of soil nutrients by crops to a certain extent.

[0062] Obviously, the above embodiments are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. However, these obvious changes or modifications derived from the spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. A highly efficient phosphate-dissolving bacteria, characterized in that: The deposit number is GDMCC No: 65495.

2. Use of the efficient phosphate-dissolving bacteria as claimed in claim 1 in promoting plant growth.

3. Use of the efficient phosphate-dissolving bacteria as claimed in claim 1 in producing siderophores and indoleacetic acid.

4. Use of the efficient phosphate-dissolving bacteria as claimed in claim 1 in promoting the growth of navel orange seedlings.

5. Use of the efficient phosphate-dissolving bacteria as claimed in claim 1 in reducing the chlorophyll b content of navel orange seedlings.

6. A fertilizer, characterized in that: Contains the highly efficient phosphate-dissolving bacteria as described in claim 1.

7. A soil conditioner, characterized in that: Contains the highly efficient phosphate-dissolving bacteria as described in claim 1.

8. A method for screening highly efficient phosphate-dissolving bacteria, characterized in that: The following steps are involved: A. Collect soil samples 10-30 cm below the drip line of navel orange trees with high yield in previous years in navel orange orchards in Xinfeng County and Gan County of Ganzhou City, mix the soil samples evenly, take 5 g of samples from the evenly mixed soil to make a soil suspension, and place the soil suspension in a constant temperature shaking water bath at 80°C and 180 r / min for 15 min; then dilute the soil suspension into gradient dilutions by a ten-fold dilution separation method, and take 100 μL of the dilutions and spread them on culture medium plates; finally, pick out single colonies on the culture medium and purify them for 2-3 generations by plate streaking method, then inoculate the purified colonies on slant culture medium and store them at 4°C to obtain the screened strains; B. Inoculate the selected strains onto inorganic phosphorus culture medium and culture for 7 days. Colonies with clear transparent circles are highly efficient phosphate-dissolving bacteria.

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