Application of brassinolide in improving resistance of sugarcane to smut

Abstract

The invention discloses application of brassinolide in improving resistance of sugarcane to smut. According to the method, brassinolide is sprayed on leaf surfaces, so that the brassinolide can improve the resistance of sugarcane to smut caused by sugarcane smut, the morbidity of sugarcane plants infected by sugarcane smut is remarkably reduced, and the influence of sugarcane smut on the yield and quality of sugarcane is reduced. Therefore, the invention provides application of brassinolide in improving or preparing a product for improving the resistance of sugarcane to smut. The method is beneficial to green control of sugarcane smut, and is simple to operate and good in feasibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of plant disease prevention and control, and more specifically relates to the application of brassinolide in improving sugarcane resistance to smut. Background Art

[0002] Sugarcane (Saccharum officinarum L.) is an important sugar crop grown in tropical and subtropical regions, producing approximately 70% of the world's sucrose. Sugarcane smut, a fungal disease caused by Sporisorium scitamineum, reduces sugarcane yield and causes severe economic losses to the sugarcane industry, making it considered one of the most economically damaging diseases.

[0003] Breeding disease-resistant varieties is considered the most cost-effective method for combating sugarcane smut. However, sugarcane breeding is inefficient and time-consuming, and sugarcane genetics are complex, with unknown disease resistance information for some key parents. As a result, many resistant varieties developed fail to meet production requirements and cannot be effectively promoted. Furthermore, the resistance of resistant varieties can change with the emergence of new subspecies. Furthermore, the thick and waxy bark of sugarcane stems makes it difficult for chemical agents to penetrate the stems and kill the pathogen, while also causing environmental pollution and pesticide residues. Therefore, the development of green control products and methods that effectively combat sugarcane smut is needed. For example, applying a certain amount of soluble silicate fertilizer during sugarcane cultivation can improve sugarcane's resistance to smut, but this method is costly.

[0004] Brassinolide (BR) is a class of steroid hormones with high physiological activity that promotes plant growth and development, participating in the regulation of processes such as seed germination, vegetative growth, reproductive growth, and responses to environmental stress. For example, BR can alleviate the toxic effects of Verticillium dahlia on cotton callus; soaking rapeseed in 0.015% BR for 6 hours reduced the incidence of sclerotinia rot by 10%; and spraying 0.2 μmol / L of BR reduced the accumulation of mosaic virus in zucchini leaves. However, the same substance has different effects on resistance to different pathogens and different plants and diseases. For example, brassinolide inhibited hyphal extension of Pyricularia oryzae and altered its colony morphology; however, the addition of brassinolide did not affect the spore morphology and growth of Trichoderma spp. For example, treating peanut seedlings with nanosilicon (SiO2) can improve their resistance to bacterial wilt; spraying Arabidopsis thaliana with nanosilicon effectively protects them from infection with Pseudomonas syringae; and while applying different doses of nanosilicon to sugarcane can reduce the incidence of sugarcane smut to varying degrees, the effectiveness has not reached a significant level. Currently, there are no reports that brassinolide can affect sugarcane smut resistance. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides an application of brassinolide in improving the resistance of sugarcane to smut.

[0006] The first object of the present invention is to provide a use of brassinolide in improving the resistance of sugarcane to smut.

[0007] The second object of the present invention is to provide a use of brassinolide in preparing a product for improving the resistance of sugarcane to smut.

[0008] The third object of the present invention is to provide the use of brassinolide in preventing and controlling sugarcane smut.

[0009] A fourth object of the present invention is to provide a use of brassinolide in preparing a product for preventing and controlling sugarcane smut.

[0010] A fifth object of the present invention is to provide a method for improving the resistance of sugarcane to smut.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] The present invention, by spraying different concentrations of brassinolide on the leaves of sugarcane plants infected with the fungus Saccharum officinale, found that spraying a certain concentration of brassinolide can improve sugarcane's resistance to smut caused by the fungus, significantly reduce the incidence of infection in sugarcane plants infected with the fungus, and mitigate the impact of the fungus on sugarcane yield and quality. Therefore, the present invention claims the use of brassinolide to improve sugarcane's resistance to smut.

[0013] The present invention also claims the use of brassinolide in preparing a product for improving the resistance of sugarcane to smut.

[0014] The present invention also claims protection for the use of brassinolide in preventing and controlling sugarcane smut.

[0015] The present invention also claims the use of brassinolide in preparing products for preventing and controlling sugarcane smut.

[0016] In a specific embodiment of the present invention, the brassinolide is 2-4-epibrassinolide.

[0017] Specifically, the smut is caused by infection by Sporisorium scitamineum.

[0018] The present invention also provides a method for improving the resistance of sugarcane to smut, comprising spraying a brassinolide solution with a concentration of 0.02 mg / L to 1.0 mg / L on sugarcane leaves, so that the leaves are covered with droplets but no droplets fall.

[0019] Specifically, the method is as follows: when the sugarcane has expanded to 3 leaves and 1 heart, a brassinolide solution with a concentration of 0.02 mg / L to 1.0 mg / L is sprayed on the sugarcane leaves for the first time, so that the leaves are covered with droplets but no droplets fall. Thereafter, the solution is sprayed every 6 to 8 days, for a total of 2 to 5 sprayings.

[0020] More specifically, spraying is performed every 6 to 8 days thereafter, for a total of 3 to 4 times.

[0021] In a specific embodiment of the present invention, spraying is performed once every 7 days, for a total of 3 times.

[0022] Preferably, the concentration of the sprayed brassinolide solution is 0.08 mg / L to 0.12 mg / L. Within this concentration range, the effect of improving sugarcane's resistance to smut is more significant.

[0023] More preferably, the concentration of the sprayed brassinolide solution is 0.1 mg / L.

[0024] In a specific embodiment of the present invention, the brassinolide is 2-4-epibrassinolide.

[0025] The present invention has the following beneficial effects:

[0026] The present invention, through foliar spraying of brassinolide, has discovered that brassinolide can enhance sugarcane's resistance to smut caused by Ustilago saccharina, significantly reducing the incidence of smut-infected sugarcane plants and alleviating the impact of smut on sugarcane yield and quality. Consequently, the present invention provides the use of brassinolide for enhancing or preparing products for enhancing sugarcane's smut resistance. This invention facilitates green control of sugarcane smut, is simple to operate, and has good feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure shows the effect of brassinolide on the spore morphology of sugarcane whip smut fungus; 0, 0.02, 0.1, and 1.0 in the figure represent different concentrations (mg / L) of brassinolide; "+" and "-" represent haploid spores.

[0028] Figure 2 The figure shows the effect of brassinolide on the mycelial morphology of Ustilago canefolia; 0, 0.02, 0.1, and 1.0 in the figure represent different concentrations (mg / L) of brassinolide.

[0029] Figure 3 The effect of brassinolide on the mycelial growth of sugarcane whip smut fungus.

[0030] Figure 4 The figure shows the effect of brassinolide on the resistance of sugarcane ROC22 to smut; a in the figure is the sugarcane in the CK (clear water) group; b is the sugarcane in the B1 (0.02 mg / L) group; c is the sugarcane in the B2 (0.1 mg / L) group; d is the sugarcane in the B3 (1.0 mg / L) group; the red circle is the sugarcane smut whip on the diseased plant.

[0031] Figure 5 The figure shows the effect of brassinolide on the resistance of sugarcane Yuetang 93-159 to smut; a in the figure is the sugarcane in the CK (clear water) group; b is the sugarcane in the B1 (0.02 mg / L) group; c is the sugarcane in the B2 (0.1 mg / L) group; d is the sugarcane in the B3 (1.0 mg / L) group; the red circle is the whip of sugarcane smut on the diseased plant. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0033] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0034] The brassinolide used in the present invention is 2-4 epibrassinolide (molecular formula is C 28 H 48 O6, EBR, purity greater than 98%), purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; nanosilicon (SiO2, 99.5%, 15±5nm), purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0035] Data analysis: IBM SPSS Statistics 27 software was used to perform one-way ANOVA tests among different groups (least range difference method, LSD, p < 0.05), and Graphpadprism 8.3 software was used for plotting.

[0036] Example 1 Effect of brassinolide on the spore and hyphae morphology and growth of Ustilago canefolia

[0037] The winter spores of sugarcane whip smut fungus (S. scitamineum) are nearly round in shape, of varying lengths, 5 to 6 μm in size, and brown or black in color. Four oval, transparent basidiospores are attached to the spores, two of which are of the "+" mating type and two of the "-" mating type. The "+" and "-" mating types combine to form an infectious dikaryotic mycelium. Individual "+" or "-" basidiospores are unable to form hyphae and are not pathogenic to the host, but can bud. The present invention tests the inhibitory effect of brassinolide on sugarcane whip smut fungus by culturing wild-type haploid spores in YePS liquid culture medium containing different concentrations of brassinolide. The spore morphology and mycelial growth morphology of sexually competent fungi are observed.

[0038] 1. Preparation of sugarcane whip smut fungus liquid

[0039] According to the method of Shen Wankuan et al. (2014), 2 g of wild-type haploid spores of sugarcane whip smut fungus were added to 1 L of sterile water to prepare a concentration of 5×10 6 Spore suspension of spores / mL; take an appropriate amount of spore suspension and activate it in YePS liquid culture medium, culture it at 28℃ and 200r / min until the bacterial liquid becomes turbid, and use it for subsequent experiments.

[0040] 2. Observation of haploid spore morphology

[0041] 200 μL of the activated Ustilago officinalis fungus culture was inoculated into YePS liquid culture medium containing different concentrations of brassinolide (0, 0.02, 0.1, and 1.0 mg / L). The inoculated culture medium was placed in a constant temperature shaker at 28°C and 200 rpm and cultured until it became turbid. 2 μL of the culture solution was dropped onto a glass slide, and the morphological characteristics of the haploid spores were observed under a 400x optical microscope to observe the effect of brassinolide on the spore morphology of Ustilago officinalis fungus.

[0042] 3. Observation of the growth morphology of mycelium with sexual ability

[0043] 1 μL of haploid “+” and “-” bacterial liquid was taken respectively, mixed and inoculated into YePS solid culture medium containing different concentrations of brassinolide (brassinolide concentration gradient was the same as above), and the sealed culture dish was placed in a constant temperature incubator at 28°C and cultured in the dark for 42 to 60 hours. During this period, the mycelial growth was observed regularly, and photos were taken and recorded in time to observe the effect of brassinolide on the mycelial morphology and growth of sugarcane whip smut fungus.

[0044] 4. Results

[0045] Effects of brassinolide on the spore morphology of Ustilago officinalis Figure 1 As shown. Figure 1 It can be seen that in the culture medium containing different concentrations of brassinolide (0, 0.02, 0.1, 1.0 mg / L), the morphological characteristics of the haploid spores of the "+" mating type and "-" mating type of sugarcane smut fungus were consistent with those of the control group, both showing an oblong shape, indicating that the change in brassinolide concentration had no effect on the morphology of the haploid spores of sugarcane smut fungus.

[0046] Effects of brassinolide on the mycelial morphology of Ustilago canefolia Figure 2 As shown (400 times optical microscope observation results). Figure 2 It can be seen that in the culture medium containing different concentrations of brassinolide (0, 0.02, 0.1, 1.0 mg / L), the hyphae of S. saccharum and the control were all long oval cylinders, indicating that the addition of brassinolide did not change the morphological characteristics of the hyphae.

[0047] Effects of brassinolide on the mycelial growth of sugarcane whip smut fungus Figure 3 As shown. Figure 3 It can be seen that after sexual mating, the "+" mating type and the "-" mating type can normally form white velvety hyphae in culture media with different concentrations of brassinolide, and the addition of brassinolide has no effect on their growth.

[0048] Example 2 Effect of brassinolide on sugarcane resistance to smut

[0049] This study used the smut-susceptible sugarcane variety New Taiwan Sugar 22 (ROC22) and the smut-resistant variety Yuetang 93-159 (both from the resource garden of the South China Agricultural University sugarcane breeding base) as experimental materials for two consecutive years to test the effects of brassinolide on sugarcane's resistance to smut. Disease-free sugarcane stalks of comparable growth, thick stem diameter, and fresh, plump buds were selected and cut into single bud segments to obtain sugarcane buds. The sugarcane buds were used in subsequent experiments, ensuring a smooth cut surface and no damage to the buds.

[0050] 1. Experiment on controlling sugarcane smut by spraying brassinolide on leaves

[0051] The sugarcane sprouts were completely immersed in a solution with a concentration of 5×10 6 Plants were incubated in a suspension of teliospores of Ustilago officinalis (Germination rate >90%) at 100 mg / mL for 30 minutes. After germination for 24 hours, the plants were moisturized and seeded in buckets (soil organic matter: 12.05 g / kg, total nitrogen: 0.65 g / kg, total phosphorus: 0.68 g / kg, total potassium: 27.55 g / kg, alkaline-hydrolyzable nitrogen: 72.63 mg / kg, available phosphorus: 79.71 g / kg, available potassium: 49.26 g / kg, pH: 6.3). Four treatments were designated CK (sprayed with an equal volume of water), B1 (sprayed with an equal concentration of 0.02 mg / L brassinolide), B2 (sprayed with an equal concentration of 0.1 mg / L brassinolide), and B3 (sprayed with an equal concentration of 1.0 mg / L brassinolide). The first spraying occurred when the sugarcane expanded to three leaves and one heart, followed by three sprayings every seven days. Brassinolide was applied foliarly, with the ideal condition being that leaves were covered with droplets but no dripping occurred. Five healthy sugarcane seedlings were planted in one bucket per treatment, with three replicates per treatment, for a total of 24 buckets for both varieties. The experimental buckets were placed in a greenhouse, and all other management procedures were standardized for local sugarcane production.

[0052] The incubation period is the period from the establishment of a parasitic relationship between the pathogen and its host to the onset of obvious symptoms. Disease counts should be taken starting with the first discovery of black smut on sugarcane (approximately 30 days after planting). Thereafter, diseased plants should be surveyed and counted every seven days for six consecutive months. During each survey, diseased plants should be labeled to avoid duplicate counts. Black smut should also be covered with sealed bags to prevent spores from spreading to other sugarcane seedlings. For details, refer to Shen Wankuan et al. (2014).

[0053] Strain incidence rate: The survey was conducted for 6 consecutive months, and the total number of strains and the total number of diseased strains were counted to calculate the strain incidence rate. The formula is as follows:

[0054]

[0055] Stem disease incidence: Survey for 6 consecutive months, count the total number of stems (main stems and tillers) and the number of diseased stems, and calculate the stem disease incidence using the following formula:

[0056]

[0057] The plant disease resistance effect and stem disease resistance effect are calculated based on the plant disease incidence rate and stem disease incidence rate. The formula is as follows:

[0058]

[0059] 2. Results

[0060] The results of the effect of brassinolide on the resistance of sugarcane to smut are shown in Table 1. As an example, the effect of brassinolide on the resistance of sugarcane ROC22 to smut is shown in Table 1. Figure 4 The effect of brassinolide on the resistance of sugarcane Yuetang 93-159 to smut is shown in Figure 5 As shown. Combined Figures 4-5 As shown in Table 1, spraying brassinolide significantly reduced the incidence of sugarcane smut under infection with Ustilago officinalis. Treatment B2 showed the most significant effect in both trials. Data from the 2023 trial showed that the incubation period for ROC22 ranged from 92 to 118 days, with treatments B1, B2, and B3 extending this period by 12, 26, and 9 days, respectively, compared to the control. The plant and stem disease incidence rates in the B2 treatment were significantly lower than those in the control, reaching the lowest rates of 7.24% and 7.87%, respectively. The B2 treatment achieved the highest plant and stem disease resistance, at 80.36% and 78.57%, respectively. In Yuetang 93-159, both plant and stem disease incidence rates were significantly lower in the B2 treatment than in the control, reaching 0% and achieving 100% disease resistance. According to the 2024 test data, the incubation period of ROC22 treated with B1, B2, and B3 was extended by 24, 37, and 19 days, respectively. The B2 treatment had the lowest plant and stem disease incidence rates, with significant differences. The B2 treatment also showed the highest plant and stem disease resistance, at 72.50% and 74.34%, respectively. The BR treatment of Yuetang 93-159 extended the incubation period by 14, 18, and 4 days, respectively, compared to the CK treatment. The B2 treatment had the lowest plant and stem disease incidence rates, with significant differences, and showed the best disease resistance.

[0061] Table 1 Effect of brassinolide on sugarcane resistance to smut

[0062]

[0063] Note: Different lowercase letters in the same column indicate significant differences between the values ​​(P<0.05).

[0064] Example 3 Effects of brassinolide on agronomic traits of sugarcane infected with Ustilago officinalis

[0065] In addition to testing the effect of brassinolide on sugarcane smut resistance, the present invention also tested the effect of brassinolide on the agronomic traits of sugarcane infected with sugarcane whip smut. The treatment was the same as in Example 2, and the plant height and stem diameter of the sugarcane were measured at the seedling, tillering, and jointing stages.

[0066] Table 2 shows the effects of brassinolide on plant height at various stages of sugarcane growth under infection with Ustilago officinalis. As shown in Table 2, foliar application of brassinolide increased plant height to a certain extent under infection, with the B2 treatment showing the most significant increase. Results from the 2023 trial showed that B2 treatment at the seedling stage of ROC22 significantly increased plant height by 26.62%. Treatments B1 and B2 increased plant height by 38.16% and 42.76% at the tillering stage, respectively. The three BR treatments at the jointing stage increased plant height by 6.47%, 33.62%, and 25.00%, respectively. Compared to CK, plant height of Yuetang 93-159 increased by 20.99%, 42.95%, and 38.89% after B2 treatment at the three stages, respectively. Results from the 2024 trial showed that spraying BR after inoculation significantly increased plant height in both varieties. In terms of plant height, the B2 treatment showed the most significant improvement at the seedling, tillering and jointing stages of ROC22, while the other treatments showed varying degrees of improvement. For Yuetang 93-159, the B2 treatment increased plant height by 18.75% at the seedling stage, and the most significant improvement was at the tillering and jointing stages, reaching 64.60 cm and 146.00 cm respectively.

[0067] Table 2 Effects of brassinolide on plant height of sugarcane at different stages infected by Ustilago officinalis

[0068]

[0069] Note: Different lowercase letters in the same column indicate significant differences between the values ​​(P<0.05).

[0070] Table 3 shows the effects of brassinolide on sugarcane stem diameter at various growth stages under infection with the fungus smut. As shown in Table 3, foliar application of brassinolide increased sugarcane stem diameter to a certain extent under infection with the fungus, with the B2 treatment showing the most significant increase. Results from the 2023 trial showed that B2 treatment increased stem diameter by 21.39% at the seedling stage for ROC22, 40.89% at the tillering stage, and 45.80% and 12.09% at the jointing stage for B2 and B3, respectively. For Yuetang 93-159, B2 treatment increased stem diameter by 49.37%, 62.74%, and 31.40% at the three growth stages, respectively. The test results in 2024 showed that in terms of stem diameter, the B2 treatment in the three periods of ROC22 had the largest increase of 27.16%, 40.48% and 25.03% respectively; the stem diameter of Yuetang 93-159 in the three periods increased to varying degrees, and the effect of B2 treatment reached a significant level, increasing by 30.52%. The BR treatment in the tillering stage increased by 18.70%, 25.95% and 4.83% respectively, and the three BR treatments in the jointing stage increased by 4.11%, 14.40% and 0.35% respectively.

[0071] Table 3 Effects of brassinolide on the stem diameter of sugarcane at different stages infected by Ustilago officinalis

[0072]

[0073] Note: Different lowercase letters in the same column indicate significant differences between the values ​​(P<0.05).

[0074] Example 4 Effect of brassinolide on the yield and quality of sugarcane stems infected with Ustilago officinalis

[0075] The present invention also tested the effect of brassinolide on the yield and quality (hammer sugar content) of sugarcane stems infected with sugarcane whip smut fungus. The treatment was the same as in Example 2, and the results are shown in Table 4. As can be seen from Table 4, there was no significant difference in the sugar brix of the sugarcane in the group sprayed with brassinolide on the leaves and the control group. From the yield analysis, spraying BR increased the yield of sugarcane to a certain extent, and the B2 treatment had the most significant improvement effect. From the test results in 2023, it can be seen that compared with CK, the yield of variety ROC22 increased by 41.52%, 44.04% and 16.33% in the B1, B2 and B3 treatments, respectively, and that of Yuetang 93-159 increased by 58.19%, 64.25% and 29.68%, respectively, among which the B2 treatment showed a significant improvement. According to the test results in 2024, the yield increases of B1, B2 and B3 treatments of ROC22 were 11.82%, 60.00% and 14.55% respectively, and those of Yuetang 93-159 increased by 23.21%, 58.93% and 26.79% respectively. There were significant differences between the three BR treatments and CK.

[0076] Table 4 Effects of brassinolide on sugarcane stem yield and sugar content under infection of Ustilago officinalis

[0077]

[0078] Note: Different lowercase letters in the same column indicate significant differences between the values ​​(P<0.05).

[0079] Comparative Example 1 Effect of Nano-Silicon on Sugarcane Whip Ustilago and Sugarcane Resistance to Smut

[0080] In the process of developing a green control product and method capable of effectively resisting sugarcane smut, the present invention uses nano-silicon in addition to brassinolide.

[0081] 1. Effects of nano-silicon on the morphology and growth of spores and hyphae of sugarcane whip smut fungus

[0082] The effect of nano-silicon on the morphology and growth of spores and hyphae of Ustilago canefolia was tested using the same method as in Example 1. The concentrations of nano-silicon in the YePS liquid culture medium containing nano-silicon were 0, 15, 30, and 45 mmol / L, respectively.

[0083] Observations under an optical microscope revealed that regardless of the concentration of nanosilicon, the morphology of the fungi remained unchanged from the control group, maintaining a typical oval shape. Mycelial morphology also remained unchanged from the blank control when cultured in media containing different concentrations of nanosilicon (0, 15, 30, and 45 mmol / L). These results indicate that nanosilicon has no effect on the morphology and growth of spores and mycelium of the sugarcane whip fungus.

[0084] 2. Effect of nano-silicon on sugarcane resistance to smut

[0085] The experiment was carried out in 2023, with four concentration gradients of nanosilicon and a total of eight treatments, as shown in Table 5 below.

[0086] Table 5 Nano-silicon soil mixing test

[0087]

[0088]

[0089] Refer to Deng Quanqing (2018) to calculate the appropriate amount of silicon application. For every 10 kg of soil, nano-silicon was mixed into the soil in advance (mix thoroughly) to prepare soils containing different amounts of nano-silicon. One bucket was planted for each treatment, with 5 healthy seedlings planted in each bucket. Each treatment was repeated 3 times. Using immersion inoculation, the sugarcane buds were completely immersed in a concentration of 5×10 6 Plants were immersed in a suspension of teliospores of Ustilago officinalis at a concentration of 100 μg / mL (germination rate exceeding 90%), then germinated for 30 minutes and planted 24 hours later. Disease statistics were performed using the method described in Example 2, and plant incidence, stem incidence, plant resistance, and stem resistance were calculated. The effects of nano-silicon on sugarcane's resistance to smut are shown in Table 6. As shown in Table 6, while the application of nano-silicon reduced the incidence of sugarcane smut to some extent and improved its resistance to disease, the overall effect was not significant.

[0090] Table 6 Effects of nano-silicon on sugarcane resistance to smut

[0091]

[0092] Note: The same lowercase letters in the same column indicate no significant difference between the values ​​(P>0.05).

[0093] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. Application of brassinolide in improving sugarcane resistance to smut.

2. Use of brassinolide in the preparation of a product for improving sugarcane resistance to smut.

3. Application of brassinolide in preventing and controlling sugarcane smut.

4. Application of brassinolide in the preparation of products for preventing and controlling sugarcane smut.

5. The use according to any one of claims 1 to 4, characterized in that: The brassinolide is 2-4-epibrassinolide.

6. The use according to any one of claims 1 to 4, characterized in that: The smut is caused by Ustilago canefolia.

7. A method for improving sugarcane resistance to smut, characterized in that: A brassinolide solution with a concentration of 0.02 mg / L to 1.0 mg / L is sprayed on sugarcane leaves so that the leaves are covered with droplets but no droplets fall.

8. The method according to claim 7, characterized in that A brassinolide solution with a concentration of 0.08 mg / L to 0.12 mg / L is sprayed on sugarcane leaves.

9. The method according to claim 7 or 8, characterized in that The brassinolide is 2-4-epibrassinolide.

10. The method according to claim 7 or 8, characterized in that When the sugarcane has expanded to 3 leaves and 1 heart, spray the brassinolide solution on the sugarcane leaves for the first time, and then spray it once every 6 to 8 days, for a total of 2 to 5 times.

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