Application of auxin in the drought stress relief of plants

Abstract

The application relates to application of Aureobasidium pullulans Cy28 in relieving drought stress of plants and belongs to the technical field of microbial application; specifically, the application of Aureobasidium pullulans Cy28 in relieving drought stress of plants, wherein the strain preservation number of the Aureobasidium pullulans Cy28 is CCTCC NO: M 2025660; the inventor first finds that the Aureobasidium pullulans Cy28 has the effect of relieving drought stress of plants, can improve the drought resistance and quality of plants, and especially can not only improve the yield of wheat but also improve the protein content of wheat kernels and the amylose content of wheat kernels.

Description

Technical Field

[0001] This invention relates to the field of microbial application technology, specifically to the application of Cy28, a budding short-stalked mold, in alleviating drought stress in plants. Background Technology

[0002] Drought is the most significant natural disaster affecting crop growth and development, and it has become one of the leading factors limiting global crop production. Overall, its impact on crop yield reduction exceeds the combined reduction caused by other factors. Drought not only affects crop growth and development and the structure of the rhizosphere microbial community, but also increases soil heterogeneity, restricts nutrient migration, and increases soil oxygen levels, leading to a significant reduction in soil microbial biomass. Drought can significantly alter the structure of bacterial and fungal communities in the soil and promote the enrichment of drought-resistant microorganisms. Studies have shown that specific rhizosphere bacteria can enhance crop drought resistance and mitigate the effects of drought stress on crop growth and development.

[0003] Drought has a significant impact on wheat, affecting not only yield but also quality. Therefore, researching and developing methods to improve wheat's drought resistance is of great importance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides the application of Cy28, a budding short-stalked mold, in alleviating drought stress in plants.

[0005] The technical solution of the present invention is as follows: Application of *Syngonium buddingae* Cy28 in alleviating drought stress in plants, wherein the preservation number of *Syngonium buddingae* Cy28 is CCTCC NO: M 2025660.

[0006] Preferably, the plant is wheat.

[0007] Preferably, the application of Cy28 in alleviating wheat drought stress is specifically its application in at least one of increasing wheat yield and improving wheat grain quality.

[0008] More preferably, the improvement of wheat grain quality specifically refers to the application of at least one of increasing wheat grain protein content and increasing wheat grain amylose content.

[0009] Preferably, the application of Cy28 in alleviating drought stress in wheat specifically involves at least one of the following: increasing the relative water content of wheat leaves, increasing the POD activity of wheat leaves, and reducing the MDA content of wheat leaves.

[0010] Preferred application of Cy28 in alleviating plant drought stress, specifically in soil improvement.

[0011] More preferably, the soil improvement specifically includes at least one of promoting soil polysaccharide accumulation, increasing soil gibberellin content, and increasing soil auxin content.

[0012] More preferably, the soil improvement specifically refers to the promotion of plant growth-promoting microorganisms in the soil. Solicoccozyma , Pseudarthrobacter The proliferation of at least one.

[0013] Preferably, in the application, the effective viable count of *Cy28* budding short-stalked mold is 10. 8 More than 1 / mL.

[0014] The beneficial effects of the present invention include at least the following: The inventors have discovered for the first time that *Cy28*, a budding short-stalked mold, can alleviate drought stress in plants, improving their drought resistance and quality, and enhancing soil microbial diversity and the abundance of beneficial microorganisms. In particular, it alleviates drought stress in wheat, increasing the relative water content of wheat leaves, enhancing POD activity in wheat leaves, and reducing MDA accumulation in wheat leaves. *Cy28* not only increases wheat yield but also improves wheat grain protein and starch content, especially amylose content. Furthermore, *Cy28* promotes soil polysaccharide accumulation, increases soil gibberellin content, and enhances soil auxin content. Attached Figure Description

[0015] Figure 1 This is a graph showing the change in polysaccharide production of strain Cy28 over time.

[0016] Figure 2 This is a graph showing the dry weight of wheat grains.

[0017] Figure 3 This is a graph showing the MDA content in wheat flag leaves.

[0018] Figure 4 This is a graph showing the POD content in wheat flag leaves.

[0019] Figure 5 This is a graph showing the gibberellin content in the rhizosphere soil of wheat.

[0020] Figure 6 This is a graph showing the auxin content in the rhizosphere soil of wheat.

[0021] Figure 7 This is a graph showing the polysaccharide content in the rhizosphere soil of wheat.

[0022] Figure 8 In the rhizosphere soil of wheat Pseudarthrobacter A graph showing the content of microorganisms.

[0023] Figure 9 In the rhizosphere soil of wheat Solicoccozyma A graph showing the content of microorganisms.

[0024] Figure 10 This is a graph showing the percentage of plant protein in wheat grains.

[0025] Figure 11 This is a graph showing the percentage of plant starch in wheat grains.

[0026] Figure 12 This is a graph showing the percentage of plant amylose in wheat grains.

[0027] Figure 13 The images show potted plants with an absolute soil moisture content of 18-22%.

[0028] Figure 14 The images show potted plants with an absolute soil moisture content of 13-17%.

[0029] Figure 15 The images show potted plants with an absolute soil moisture content of 8-12%. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0031] Unless otherwise specified, the following examples are all conventional experimental methods and operating procedures in the art.

[0032] In the following examples, the budding short-stemmed mold Cy28 is referred to as "strain Cy28".

[0033] The preservation number of the budding short-stalked mold Cy28 is CCTCC NO: M 2025660; this strain has been disclosed in existing patent literature (publication number: CN 121379833 A, application number: 202511924300.3).

[0034] Example 1 Preparation of Cy28 strain inoculant Cy28 strain was inoculated onto PDA solid medium and cultured at 28°C for 48 h. Then, plump, viscous Cy28 colonies were inoculated onto PDB liquid medium and cultured at 28°C with shaking at 180 rpm for 72 h to obtain the Cy28 budding short-stem fungus fermentation broth. The fermentation broth was transferred to a sterile centrifuge bottle, centrifuged at 5000 rpm for 5 min to collect the cells, washed with sterile deionized water, resuspended, and the bacterial concentration was adjusted to 5 × 10⁻⁶. 8 cfu / mL, yielding Cy28 bacterial agent.

[0035] Example 2 Polysaccharide yield of microbial agent Cy28 in fermentation broth Add 3 kg of soil to 9 L of deionized water, shake at 180 rpm for 48 h, centrifuge at 6000 rpm for 15 min, collect the supernatant, filter through a 0.45 μm microporous membrane and sterilize; then mix it evenly with sterile basic fermentation medium at a volume ratio of 2:1 to prepare a sterile mixture; the mass concentrations of each component of the sterile basic fermentation medium are: beef extract 3.0 g, peptone 5.0 g, glucose 10.0 g, distilled water 1.0 L, pH 7.0. Take 200 mL of the mixture and add it to an Erlenmeyer flask, set up 3 parallel operations, and add 10% (LN) and 20% (MN) of PEG6000 (polyethylene glycol 6000) to the prepared mixture respectively; use no PEG6000 as a control. The Cy28 bacterial agent prepared in Example 1 was inoculated at a rate of 1% (v:v) and cultured at 28°C and 180 rpm. Samples were taken at 0, 12, 24, 36, 48, 60, 72, 84, 96, 108, and 120 h to determine the polysaccharide content in the culture medium. The polysaccharide content was determined by extracting polysaccharides from the supernatant using an alcohol extraction method, and the polysaccharide content was measured using the phenol-sulfuric acid method to calculate the yield.

[0036] Depend on Figure 1 As shown, under the control group (CK), the polysaccharide yield in the fermentation broth of strain Cy28 reached its highest level of 3.74 g / L around 84 h of culture. Under mild drought stress (LN) treatment, the polysaccharide yield of strain Cy28 was significantly higher than that of the control group, with a maximum yield of 4.29 g / L, and the overall synthesis trend was similar to that of the control. Under moderate drought stress (MN) treatment, the polysaccharide yield of strain Cy28 was further increased, and remained higher than that of the LN and CK groups throughout the entire culture period, also reaching its maximum yield around 84 h, with a maximum yield of 4.56 g / L. Overall, this indicates that simulated drought stress can significantly promote the synthesis of extracellular polysaccharides by strain Cy28, and the promoting effect is more pronounced under moderate drought stress (MN). The polysaccharide in the fermentation broth of strain Cy28 is pullulan.

[0037] Example 3 The regulatory effect of Cy28 inoculant on wheat grain nutrition and processing quality under drought stress The microbial inoculant Cy28 was applied to a wheat pot experiment as follows: Plump, surface-sterilized seeds of Ji 22 winter wheat were sown in flowerpots, and after germination, the seedlings were thinned to 10 plants / pot. The Cy28 inoculant prepared in Example 1 was diluted with sterile deionized water to a concentration of 1×10⁻⁶. 8The number of cells / mL was controlled with sterile deionized water (CK). During the tillering stage of wheat, trenches (1-2 cm deep) were dug around the roots. Cy28 strain (F), sterilized Cy28 strain (DF), and pullulan polysaccharide solution (P) at a concentration of 2 g / L were added to the trenches, with a total addition volume of 100 mL per pot. Each pot contained 10 kg of soil. Water stress was applied one week after the wheat flowering period until the absolute soil moisture content reached 18-22% (CK), 13-17% (LN), and 8-12% (MN). Measurements were taken daily at 18:00, and water control was performed every two days. Moisture content was measured one hour after water treatment until it stabilized. Each treatment was repeated three times. Potted plants were grown in a greenhouse (temperature 15-24℃, relative humidity 10-30%, normal light). The entire wheat growth cycle was 210 days, and the growth status was as follows. Figure 13 , Figure 14 , Figure 15 As shown. By Figure 2The study investigated the changes in dry weight of winter wheat grains after moisture control treatment. Under the same moisture conditions, compared with the CK (control group) and DF (sterilized Cy28 strain group) treatments, the exogenous P (pullulan group) and F (Cy28 strain group) treatments significantly altered wheat grain dry weight (wheat grain dry weight refers to the dry weight of wheat grains per pot), with significant differences among the treatments. Compared with the CK and DF treatments without exogenous substances under the same moisture conditions, the application of pullulan under mild drought stress significantly increased wheat grain dry weight. Under moderate drought stress, pullulan could still effectively alleviate the dry weight reduction caused by drought. The Cy28 strain treatment showed a more significant increase in grain dry weight under LN and MN stress environments, indicating that the application of exogenous pullulan and Cy28 strains can effectively alleviate the inhibitory effect of drought stress on grain dry matter accumulation and improve wheat grain development under drought stress. Meanwhile, although pullulan treatment could increase grain dry weight to varying degrees under different moisture gradients, its yield-increasing effect was significantly weaker than that of strain Cy28 treatment. There was no significant difference in grain dry weight between strain Cy28 post-sterilization treatment and deionized water CK under the three moisture environments, indicating that strain Cy28 post-sterilization treatment could not effectively alleviate the problem of drought-induced inhibition of grain dry matter accumulation. In the CK and DF groups without exogenous improvement measures, wheat grain dry weight showed a significant decreasing trend as drought stress intensified from mild (LN) to moderate (MN), indicating that the inhibitory effect of drought stress on grain filling and dry matter accumulation gradually increased. Exogenous application of pullulan and strain Cy28 could significantly reverse the grain dry weight loss caused by drought stress and effectively promote grain dry matter transport and accumulation under stress conditions. Among these, strain Cy28 treatment showed the highest grain dry weight among all groups under normal water supply, mild drought, and moderate drought conditions. This indicates that exogenous pullulan and strain Cy28 can significantly alleviate the hindered development of wheat grains caused by drought stress, increase grain dry weight, and reduce the adverse effects of drought on grain formation. Moreover, strain Cy28 has a significantly better regulatory and synergistic effect on wheat grains under drought stress than pullulan.

[0038] Depend on Figure 10 , Figure 11 , Figure 12It was found that after different gradients of drought stress treatment, the percentages of plant protein, plant starch (wheat grain starch), and plant amylose in wheat grains were determined using the Kjeldahl method, double-enzyme digestion-spectrophotometry, and iodine colorimetric spectrophotometry, respectively. The regulatory effects of Cy28 inoculant (F), sterilization group (DF), and pullulan (P) on the nutritional processing quality of wheat were systematically analyzed. Under the same moisture conditions, compared with deionized water (CK) and sterilization group (DF), exogenous pullulan and active Cy28 inoculant treatments significantly improved the three key quality indicators of wheat grains: amylose, plant starch, and protein, with significant statistical differences among the treatment groups. There were no significant differences in the amylose, plant starch, and protein content of wheat grains between the sterilization group and deionized water (CK) under the three moisture conditions, indicating that inactivated Cy28 bacteria could not alleviate the negative inhibitory effect of drought stress on the nutritional quality of wheat grains, and the physiological metabolic activity of live Cy28 bacteria is the core basis for improving wheat quality.

[0039] Under three water gradients—normal water supply (CK), mild drought (LN), and moderate drought (MN)—the percentages of amylose, plant starch, and protein in wheat grains all showed a significant decreasing trend with increasing drought stress, particularly in the deionized water (CK) and sterilized (DF) control groups. Drought stress significantly inhibits starch synthesis and nitrogen translocation during the wheat grain-filling stage, leading to simultaneous deterioration in both grain processing and nutritional quality. Compared to the CK and DF control groups under the same water conditions, exogenous pullulan (P) significantly increased the content of amylose, plant starch, and protein in the grains, effectively alleviating the damage to wheat quality caused by drought stress. Furthermore, the active Cy28 inoculant (F) treatment showed significantly higher percentages of amylose, plant starch, and protein under all water conditions (CK, LN, and MN) than all other treatment groups, demonstrating a significantly greater improvement in quality than the pullulan P treatment and exhibiting a strong ability to regulate and improve quality under drought conditions.

[0040] From the perspective of starch nutritional characteristics, the F treatment with Cy28 inoculation can significantly increase the amylose content of wheat grains. Increased amylose content helps increase the proportion of resistant starch in the grains. Resistant starch is not easily digested and absorbed by the human small intestine, thus stabilizing postprandial blood glucose levels and possessing significant potential application value for developing low-GI functional wheat staple foods. Simultaneously, combined with the grain protein percentage results, it is evident that Cy28 inoculation treatment can synergistically improve two core quality components: gluten protein is the material basis for the elasticity and extensibility of wheat dough, while amylose directly determines the smoothness, cooking resistance, and shaping stability of steamed and boiled pasta. Simultaneous improvement of both can synergistically optimize the processing applicability of Jimai 22 noodles and dumpling wrappers, enhancing dough strength, reducing the probability of breakage and tearing during steaming and boiling, and improving the smoothness of pasta texture while reducing stickiness after steaming and boiling.

[0041] The combined results of the three sets of indicators clearly show that exogenous application of pullulan polysaccharide and active Cy28 inoculant can significantly reverse the loss of wheat grain nutritional quality caused by drought stress, promote starch synthesis and nitrogen translocation and accumulation in grains during the grain-filling period, and alleviate the inhibitory effect of drought on grain quality formation. Among them, Cy28 live bacteria treatment has the best effect on improving the content of amylose, plant starch and protein in grains. While improving the processing characteristics of wheat, it also enhances the nutritional and health value of grains, and can provide high-quality microbial regulation technology support for the cultivation of high-quality functional wheat in arid areas.

[0042] Example 4 Effects of Cy28 inoculant on antioxidant physiological properties of wheat flag leaves under drought stress To investigate the regulatory mechanism of Cy28 microbial inoculant on the physiological resistance of wheat under drought stress, wheat pot plants (Example 3) were used. After 1 and 2 weeks of water stress treatment, flag leaves from the same part of the wheat plants were uniformly selected for physiological index determination. Leaf samples were divided into two portions. 0.1g of fresh leaves were accurately weighed, and malondialdehyde (MDA) content and antioxidant enzyme activities such as peroxidase (POD) were determined using ELISA kits (models JM 110029P1, JM 09865P2, JM 01183P2, JM 01185P2) from Jiangsu Nanjing Biotechnology Co., Ltd. The other sample was used to determine the soluble protein content of the leaves. After the wheat cultivation experiment, aboveground wheat plants and rhizosphere soil were collected from each treatment group for subsequent index testing. Wheat ears were separated using sterilized stainless steel scissors to determine agronomic traits. The remaining aboveground plants were washed sequentially with 0.01M sodium ethylenediaminetetraacetate (EDTA-2Na) and distilled water, blanched at 105℃ for 30 min, and dried at 60℃ to constant weight before weighing. Combined with leaf physiological indicators, the regulatory effect of Cy28 inoculant on wheat physiological metabolism under drought stress was systematically analyzed.

[0043] Depend on Figure 3It was found that the malondialdehyde (MDA) content in the flag leaves of winter wheat showed significant differences under different drought stress treatments and water gradients (P<0.05). MDA is a core physiological indicator reflecting the degree of lipid peroxidation in plant cell membranes and measuring stress damage; its content directly represents the degree of damage to plant cell membranes. The experimental results showed that compared with the deionized water control and sterilization group, Cy28 live bacteria inoculation treatment significantly reduced the accumulation of MDA in wheat flag leaves. Among them, under mild drought stress, the MDA content in the flag leaves of the Cy28 treatment group was significantly reduced by 24.70% compared with the uninoculated treatment; under moderate drought stress, the MDA content decreased by 39.62%, and the effect of improving quality and efficiency became more prominent with the increase of drought stress. Although pullulan treatment could alleviate MDA accumulation and reduce cell membrane oxidative damage to some extent, its regulatory effect was significantly weaker than that of Cy28 live bacteria treatment. There was no significant difference in MDA content between the sterilization group and the deionized water control group, confirming that the inactivated Cy28 strain did not have the ability to alleviate drought-induced oxidative damage in wheat, and that viable bacterial activity was key to its regulatory effect. In the deionized water control and sterilization groups without exogenous regulation, as drought stress intensified from mild to moderate, the MDA content in wheat flag leaves increased significantly, cell membrane lipid peroxidation damage continued to worsen, and the degree of inhibition of plant physiological metabolism by stress was significantly enhanced. Inoculation with the Cy28 strain effectively inhibited drought stress-induced excessive accumulation of MDA, significantly reduced cell membrane lipid peroxidation damage, stabilized the integrity of wheat leaf cell structure, and effectively alleviated the destructive effects of drought stress on the physiological functions of wheat flag leaves.

[0044] Depend on Figure 4It was found that different treatments under drought stress had a significant regulatory effect on the activity of peroxidase (POD) in the flag leaves of winter wheat, and there were significant differences in POD activity among the treatment groups (P<0.05). POD is a key antioxidant enzyme in plants, which can effectively remove excess reactive oxygen species accumulated in the plant and reduce oxidative stress damage. It is an important indicator for measuring the drought resistance of plants. The experimental data showed that under normal water supply and drought stress conditions, inoculation with Cy28 live bacteria could significantly increase the POD activity in the flag leaves of wheat. Compared with the uninoculated treatment, the POD activity in the flag leaves of the Cy28-treated group was significantly increased by 46.30% under mild drought stress, and the increase was as high as 62.96% under moderate drought stress. The stronger the drought stress, the more significant the induction and enhancement effect of Cy28 on the antioxidant enzyme activity of wheat. The POD activity of the pullulan polysaccharide treatment group was slightly higher than that of the deionized water control group and the sterilized group, but the increase was much lower than that of the Cy28 live bacteria treatment, and the regulatory effect was limited. The sterilization treatment group showed no significant difference in POD activity compared to the deionized water control group, failing to induce an increase in wheat antioxidant enzyme activity and indicating a lack of drought-resistant physiological regulation capabilities. In the uninoculated control group, wheat showed no significant increase in POD activity under drought stress, indicating that reactive oxygen species (ROS) could not be promptly cleared from the plants, leading to continuous accumulation of oxidative stress damage and a weak drought-resistant physiological response. However, inoculation with the Cy28 strain effectively activated the wheat's antioxidant defense system, significantly inducing an increase in POD activity, enhancing the plant's ROS scavenging capacity, effectively alleviating oxidative damage caused by drought stress, and ensuring normal physiological metabolism in wheat leaf cells. In conclusion, the Cy28 microbial agent can enhance the drought stress adaptability and self-repair ability of wheat plants by increasing antioxidant enzyme activity, effectively improving wheat drought resistance, maintaining normal physiological functions of wheat plants under drought conditions, and providing physiological protection for wheat to resist adverse stress and stabilize growth and metabolism.

[0045] The combined analysis of MDA content and POD activity, two antioxidant physiological indicators, revealed that drought stress significantly exacerbates oxidative damage to wheat leaf cell membranes and inhibits the plant's antioxidant defense capabilities. Cy28 live bacteria inoculation treatment alleviates wheat drought stress damage through a bidirectional regulatory mechanism: on the one hand, it significantly reduces MDA accumulation in flag leaves, mitigating cell membrane lipid peroxidation and protecting cell structural integrity; on the other hand, it significantly induces increased POD antioxidant enzyme activity, enhancing the plant's reactive oxygen species scavenging capacity. Furthermore, the experimental results confirmed that the live biological activity of the Cy28 strain is the core key to its drought-resistant physiological regulatory function; neither single polysaccharide components nor inactivated bacteria can achieve a significant antioxidant synergistic effect. Overall, the Cy28 inoculant can effectively improve the drought tolerance of winter wheat (Ji 22) by optimizing the wheat's antioxidant physiological system and alleviating drought-induced oxidative stress damage, providing an important microbial regulatory basis for wheat plants to maintain normal physiological metabolism and ensure growth stability under drought conditions.

[0046] Example 5 Strain Cy28 enhances the detection of rhizosphere soil gibberellins and other soil-related physicochemical properties. Rhizosphere soil samples were collected from the wheat pot experiment in Example 3, and the contents of gibberellin (GA) and auxin (IAA) in the soil were determined. The contents of GA and IAA in the soil were determined using an enzyme-linked immunosorbent assay (ELISA) kit, and the operation was strictly performed in accordance with the kit instructions.

[0047] The anthrone-sulfuric acid colorimetric method was used to determine the content of soil polysaccharides. Soil samples were prepared by hot water extraction, centrifugation and filtration. A standard curve was plotted with glucose, and anthrone-sulfuric acid reagent was added for color development in a boiling water bath. After cooling, the absorbance was measured at 620 nm. The content of soil polysaccharides was calculated based on the standard curve. Technical replication was set for each sample to ensure data reliability.

[0048] like Figure 5 , Figure 6 As shown, compared with the sterilization control, inoculation with strain Cy28 significantly altered the levels of GA and IAA in wheat rhizosphere soil under different moisture conditions. Under soil absolute moisture contents of 18-22% (CK), 13-17% (LN), and 8-12% (MN), inoculation treatments significantly increased the contents of GA and IAA in the rhizosphere soil. Regarding gibberellin content: under LN stress, the GA content in the inoculated group (F) reached its peak, significantly higher than that in the deionized water group (CK), sterilization group (DF), and pullulan group (P) under the same moisture conditions. Overall, the increase in GA content was most significant under LN treatment, followed by MN conditions, while the CK condition still maintained a significant increasing effect. Regarding auxin content: consistent with the trend of GA, the IAA content of the inoculated group (F) under LN stress reached the maximum value, which was significantly higher than that of other treatments; under CK and MN conditions, the IAA content of the inoculated group and pullulan polysaccharide group (F, P) was also significantly higher than that of the uninoculated control, and the overall content level showed LN > CK > MN.

[0049] Depend on Figure 7It can be seen that the water control treatment and different exogenous treatments significantly altered the polysaccharide content in the rhizosphere soil of wheat. Under the three water conditions of CK, LN, and MN, the application of exogenous pullulan and strain Cy28 significantly increased the polysaccharide content in the rhizosphere soil, while there was no significant difference in soil polysaccharide content between the deionized water and sterilization groups under the same water conditions. Under normal water supply (CK) conditions, the soil polysaccharide content in the pullulan treatment was significantly higher than that in the deionized water and sterilization treatments. The polysaccharide content in the Cy28 treatment was the highest among all treatments in the same group and significantly higher than the other treatments. Under mild drought (LN) conditions, the overall soil polysaccharide level was higher than that under normal water supply conditions. The Cy28 treatment was still significantly higher than the deionized water, sterilization, and pullulan treatments. The pullulan polysaccharide content was significantly higher than that in the deionized water group, but not significantly different from that in the sterilization group. Under moderate drought (MN) stress, the soil polysaccharide accumulation effect was further enhanced. The polysaccharide content in the pullulan and Cy28 treatments continued to rise, with the Cy28 treatment reaching the peak value of the entire sample. The pullulan polysaccharide content was significantly higher than that in the deionized water and sterilization groups, but there was no significant difference between the deionized water and sterilization treatment groups. Overall, as the drought stress intensified from CK to LN to MN, the soil polysaccharide content in the deionized water and sterilized control groups showed a slow upward trend. The increase in soil polysaccharide under exogenous treatments of pullulan and strain Cy28 continued to increase with the intensification of drought stress. The overall soil polysaccharide content under the same treatment was MN > LN > CK. Within the same water gradient, the overall ranking of soil polysaccharide content was F > P > DF ≈ CK, indicating that the addition of exogenous P and F can effectively promote the synthesis and accumulation of rhizosphere soil polysaccharides. Moreover, the effect of strain Cy28 treatment on soil polysaccharide enhancement was significantly better than that of pullulan treatment. Drought stress can further amplify the enhancement effect of the two exogenous substances on soil polysaccharides.

[0050] Drought stress significantly altered the accumulation of rhizosphere soil polysaccharides and the balance of endogenous hormones. As the stress progressed from normal water supply (CK) to mild drought (LN) and moderate drought (MN), the rhizosphere soil polysaccharide content in the blank control group increased slightly. However, the contents of endogenous GA and IAA were generally lower under moderate drought (MN) than under CK and mild drought (LN), indicating that moderate drought had a significant inhibitory effect on the synthesis of endogenous hormones in the soil. Exogenous application of pullulan (P) and live bacteria Cy28 (F) can simultaneously regulate rhizosphere polysaccharide and hormone metabolism: On the one hand, pullulan and Cy28 treatments can significantly promote the synthesis and accumulation of rhizosphere soil polysaccharides, and the increase in polysaccharides continues to increase with the intensification of drought stress, with the overall trend being MN>LN>CK. The accumulation-promoting effect of Cy28 treatment is significantly better than that of pullulan treatment. On the other hand, Cy28 can significantly increase the content of GA and IAA in rhizosphere soil, effectively alleviating the inhibitory effect of drought on the synthesis of endogenous hormones in the soil. The regulatory gain is most prominent under mild drought LN conditions. Although pullulan treatment can slightly increase soil polysaccharides, its effect on increasing endogenous hormones is weaker than that of Cy28 treatment. The sterilized DF treatment cannot significantly improve the levels of soil polysaccharides and endogenous hormones. The above results indicate that inoculated strain Cy28 can optimize the rhizosphere microenvironment under drought conditions through a dual pathway: firstly, it promotes the enrichment of rhizosphere soil polysaccharides and improves the physicochemical environment of the rhizosphere soil; secondly, it upregulates the content of gibberellins and auxins in the soil and repairs the imbalance of endogenous hormones caused by drought stress. The two work synergistically to improve the rhizosphere microecology, thereby enhancing the physiological resilience of wheat to drought stress.

[0051] In summary, strain Cy28 has the dual function of promoting soil polysaccharide accumulation and regulating the balance of rhizosphere endogenous hormones. It can synergistically alleviate drought stress damage from the soil matrix and rhizosphere hormone levels and enhance the drought adaptability of wheat.

[0052] Example 6 Detection of soil microbial diversity by strain Cy28 Soil microbial diversity directly reflects soil fertility, soil microbial activity, and plant productivity, and it is highly sensitive to environmental responses. This study investigated the microbial diversity of wheat rhizosphere soil under different water control treatments. Bacterial genomic DNA was extracted from rhizosphere soil samples using a rapid DNA extraction kit. The extracted DNA was amplified using universal primers 338F (SEQ ID NO.1) and 806R (SEQ ID NO.2), and the amplified fragment was identified as the V4 region of bacterial 16S rRNA. The amplified fragment was then subjected to high-throughput sequencing using Illumina Hiseq2000.

[0053] The experimental results are shown in Figure 8 , Figure 9 As shown.

[0054] Depend on Figure 8 It can be seen that, under different moisture conditions, inoculation with strain Cy28 significantly altered the rhizosphere soil. Pseudarthrobacter Relative abundance of the genus. Under normal moisture conditions, the abundance of strain Cy28... Pseudarthrobacter The relative abundance was significantly higher than that of the uninoculated control group (CK), reaching approximately 2.9%; under low-intensity drought stress, the pullulan polysaccharide group... Pseudarthrobacter The relative abundance reached a peak of approximately 5.7%, significantly higher than other treatments under the same conditions; under moderate drought stress, the abundance of strain Cy28 group... Pseudarthrobacter The relative abundance increased most significantly, reaching approximately 7.6%, significantly higher than the uninoculated control group (CK) and other treatments under the same moisture conditions. Overall, drought stress significantly increased the abundance in the inoculated treatment. Pseudarthrobacter The relative abundance of the strain Cy28 was further amplified by inoculation.

[0055] Depend on Figure 9 It can be seen that, under different moisture conditions, inoculation with strain Cy28 also significantly altered the rhizosphere soil. Solicoccozyma Relative abundance of the genus. Under normal moisture conditions, strain Cy28... Solicoccozyma The relative abundance reached approximately 2.1%, significantly higher than the uninoculated CK group; under low-intensity drought stress, the Cy28 group... Solicoccozyma The relative abundance reached a peak of approximately 2.3%, significantly higher than other treatments under the same conditions; under moderate drought stress, the abundance of strain Cy28 group... Solicoccozyma The relative abundance remained at a high level, approximately 2.0%, significantly higher than the uninoculated control group (CK). Overall, the live bacteria inoculation treatment had a positive effect on... Solicoccozyma The effect of increasing relative abundance is more pronounced under normal moisture and low-intensity drought conditions.

[0056] Pseudarthrobacter and Solicoccozyma They are a group of beneficial microorganisms that play important roles in the soil. Pseudarthrobacter It is widely involved in the decomposition of soil organic matter and nutrient cycling, and can promote plant growth by producing plant hormones and dissolving mineral nutrients, while enhancing the host's tolerance to abiotic stress. Solicoccozyma As a type of functional yeast, it plays a role in improving the rhizosphere microenvironment, enhancing soil fertility, and promoting plant stress resistance. Inoculation with strain Cy28 significantly increased the relative abundance of these two key beneficial microorganisms under different moisture conditions, indicating that strain Cy28 can improve the soil microenvironment and enhance the plant's adaptability to drought stress by regulating the rhizosphere microbial community structure and enriching functional beneficial bacteria.

[0057] In summary, this invention is the first to discover that strain Cy28 can alleviate plant drought stress, maintain normal physiological characteristics of wheat, thereby reducing the adverse effects of extreme water conditions on wheat, increase wheat grain dry weight, promote plant growth, optimize plant agronomic traits, increase the starch content of wheat grains, especially amylose, increase soil microbial abundance, and increase soil enzyme activity, among other functions. It can be widely used in fields such as alleviating soil drought stress and improving crop biomass.

Claims

1. Application of *Bacillus buddingus* Cy28 in alleviating drought stress in plants, wherein the preservation number of *Bacillus buddingus* Cy28 is CCTCC NO: M 2025660.

2. The application as described in claim 1, characterized in that, The plant in question is wheat.

3. The application as described in claim 2, characterized in that, Specifically, it can be applied to at least one of the following: increasing wheat yield or improving wheat grain quality.

4. The application as described in claim 3, characterized in that, The improvement of wheat grain quality specifically refers to the application of at least one of increasing wheat grain protein content and increasing wheat grain amylose content.

5. The application as described in claim 2, characterized in that, Specifically, it involves the application of at least one of the following: increasing the relative water content of wheat leaves, increasing the POD activity of wheat leaves, and reducing the MDA content of wheat leaves.

6. The application as described in claim 1, characterized in that, Specifically, it is used to improve soil.

7. The application as described in claim 6, characterized in that, The soil improvement specifically refers to at least one of the following: promoting soil polysaccharide accumulation, increasing soil gibberellin content, and increasing soil auxin content.

8. The application as described in claim 6, characterized in that, The soil improvement specifically refers to promoting plant growth-promoting microorganisms in the soil. Solicoccozyma , Pseudarthrobacter The proliferation of at least one.

9. The application as described in claim 1, characterized in that, The effective viable count of Cy28, a budding short-stalked fungus, is 10. 8 More than 1 / mL.

Images