Bacillus velezensis K24 and application thereof

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to bacillus velezensis K24 and application thereof. The bacillus velezensis K24 provided by the invention has an inhibition effect on the growth of pathogenic bacteria such as apple pythium pathogenic bacteria, yam streak smut, potato gray mold pathogenic bacteria, potato leaf mold pathogenic bacteria, fusarium graminearum, wheat root rot and the like, and can be used for preventing and treating crop diseases; the bacillus velezensis K24 has a remarkable promoting effect on the growth of the root length of cucumber seedlings, and the root length can be increased by 29% to the maximum extent; the growth promoting effect is achieved on the stem diameter and the dry and fresh weight of cucumber seedlings, the stem diameter can be increased by 14% to the maximum extent, the fresh weight can be increased by 29.5% to the maximum extent, the dry weight can be increased by 36.9% to the maximum extent, and the method can be used for promoting growth of cucumbers.

Description

Technical Field

[0001] The invention belongs to the technical field of microorganisms, and particularly relates to a biological control function of Bacillus velezinii and an application thereof. Background Art

[0002] Although traditional chemical pesticides can effectively inhibit pathogens in a short period of time, due to the changes in the physiological subspecies of pathogens and the increase in drug resistance, the pesticide dosage needs to be continuously increased, which can easily lead to more serious disease outbreaks, soil pollution, environmental pollution, pesticide residues and other problems. Biological control is the use of interactions between microorganisms and between microorganisms and plants to achieve the inhibitory effect of beneficial microorganisms on harmful microorganisms. There are currently many microbial products, but due to their insufficient colonization in the field and short duration of effectiveness, the exploration and use of efficient microorganisms to achieve efficient and environmentally friendly biological control purposes has become one of the hot spots in current agricultural science research.

[0003] Bacillus is a representative biocontrol microorganism that has been studied in depth and widely used. Relevant literature has disclosed that Bacillus Velez can inhibit the growth of pathogens such as melon wilt and watermelon wilt, and can promote the growth of watermelon and melon. For example, patent literature has disclosed that Bacillus Velez has a high control effect on grape gray mold, and also has a good control effect on Pinus tabulaeformis blight, apple ring rot, poplar rot, walnut canker and walnut brown spot. There are also documents that disclose that Bacillus Velez has a good effect after being used in the prevention and control of cucumber bacterial angular spot. Other literature reports that Bacillus Velez can survive in a high concentration of lead environment and has a strong adsorption effect on lead. It can be used to remove lead from animal feed so that animals can grow healthily. There are also documents that disclose that the fermented liquid of Bacillus Velez has a potted prevention effect of up to 80.99% on rapeseed sclerotinia, and Bacillus Velez has good antagonistic activity to Corynespora cassiicola, and the inhibition rate of the mycelial growth of Corynespora cassiicola reaches 55%, and has good antibacterial effect on the pathogen of broccoli wilt Fusarium oxysporum. The potted effect disclosed in the above-mentioned document is better, but due to the influence of conditions such as environment and climate (such as environmental factors such as soil quality), the effect of field planting and potted planting will produce a large difference. How to make Bacillus Velez have a more ideal field planting effect, this is also a problem to be solved urgently. In addition, whether Bacillus Velez K24 has a degradation effect on ammonia nitrogen and COD of water bodies in aquaculture, this is also unknown. If it can achieve excellent results, then a new strain and method will be provided for the treatment of ammonia nitrogen and COD in water bodies in aquaculture. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a Velez subsp. K24 and its application, which can inhibit the growth of plant pathogens such as potato gray mold pathogens and promote the growth of cucumber seedlings.

[0005] The present invention provides a Bacillus velezensis K24, which is classified as Bacillus velezensis, deposited in Guangdong Microbiological Culture Collection Center, with a deposit number of GDMCCNO.64095, a deposit date of December 1, 2023, and a deposit address: Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou. The Bacillus velezensis K24 described in the specific embodiments refers to the strain numbered above.

[0006] The present invention also protects an agricultural microbial agent, the active ingredient of which is Bacillus Velez K24.

[0007] In addition, the present invention also protects the use of the above-mentioned Bacillus Velez K24 or agricultural microbial agents containing Bacillus Velez K24 in inhibiting the growth of plant pathogens; and their use in promoting the growth of vegetable seedlings, such as cucumbers, melons and other vegetables or fruits, but is not limited to the two listed above.

[0008] The above-mentioned plant pathogens include: apple rot pathogens, yam stripe smut, potato gray mold pathogens, potato leaf mold pathogens, Fusarium graminearum and wheat root rot umbilical worm spores; after investigation, it was found that the Bacillus Velez K24 provided by the present invention not only has an inhibitory effect on the growth of common Rhizoctonia solani, melon wilt pathogens (specifically, Fusarium oxysporum melon transformation type), watermelon wilt pathogens and bitter melon wilt pathogens, but also has a strong inhibitory effect on the growth of apple rot pathogens, yam stripe smut, potato gray mold pathogens, potato leaf mold pathogens, Fusarium graminearum, wheat root rot umbilical worm spores and other pathogens.

[0009] The application of the above-mentioned Bacillus Velez K24 in degrading ammonia nitrogen and / or COD in water bodies in aquaculture is also within the scope of protection of the present invention.

[0010] The beneficial effects of the present invention are:

[0011] (1) The Bacillus Velez K24 in the present invention includes a bacterial agent containing Bacillus Velez, which has an inhibitory effect on the growth of pathogens of apple rot, yam stripe smut, potato gray mold, potato leaf mold, Fusarium graminearum, and wheat root rot helminth spores, and can be used for the prevention and control of crop diseases and insect pests;

[0012] (2) The Velez subtilis K24 of the present invention includes a bacterial agent containing Velez subtilis, which has a significant promoting effect on the growth of vegetables, especially cucumber seedling roots, and can increase the cucumber root length by about 29% at most; it has a growth promoting effect on the stem thickness and dry and fresh weight of cucumber seedlings, and can increase the stem thickness by 14%, the fresh weight by 29.5%, and the dry weight by 36.9% at most, and can be used to promote the growth of cucumbers. Similarly, the bacterial agent of the present invention has a very obvious effect on preventing diseases and promoting growth of melons, as shown in the corresponding description and data in the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The inhibition of Bacillus Velez K24 on different plant pathogens;

[0014] Figure 2 The effect of different application rates of Bacillus Velez K24 on the root length of cucumber seedlings;

[0015] Figure 3 The effect of different application rates of Bacillus Velez K24 on the stem diameter of cucumber seedlings;

[0016] Figure 4 The effect of different application rates of Bacillus Velez K24 on the fresh weight of cucumber seedlings;

[0017] Figure 5 The effect of different application rates of Bacillus Velez K24 on the dry weight of cucumber seedlings;

[0018] Figure 6 The effect of different application rates of Bacillus Velez K24 on the growth of cucumber seedlings;

[0019] Figure 7 The inhibition rates of Bacillus Velez K24, Bacillus Velez K22 and Bacillus subtilis K61 against several different diseases such as apple rot pathogens;

[0020] Figure 8 The results of the confrontation between Bacillus Velez K24, Bacillus Velez K22, and Bacillus subtilis K61 and the pathogen plate;

[0021] Fig. 9 It is the disease index of melon grown in diseased soil under different flushing rates of Bacillus Velez K24;

[0022] Fig.10 The effect of different application rates of Bacillus Velez K24 on the growth of melon seedlings cultivated in diseased soil;

[0023] Fig.11 The effect of different application rates of Velez fungicide K24 on SPAD values ​​of melon leaves grown in diseased soil;

[0024] Fig.12 The effect of different application rates of Bacillus Velez K24 on plant height and root length of melon cultivated in diseased soil;

[0025] Fig.13 The effect of different application rates of Bacillus Velez on stem diameter of melon seedlings grown in diseased soil.

[0026] Fig.14 The effect of different application rates of Velez fungicide on the fresh and dry weight of melon seedlings grown in diseased soil.

[0027] Fig.15 It is the COD concentration variation diagram in Example 5;

[0028] Fig.16 is the change of ammonia nitrogen concentration in Example 5;

[0029] Fig.17 The control effect of applying Veles on bitter gourd wilt in the field in Example 6 is shown. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in conjunction with specific implementation methods.

[0031] Example 1 Inhibitory Effect of Bacillus Velezii K24 on Plant Pathogens

[0032] S1. Activation of plant pathogens

[0033] The plant pathogens stored in the glycerol tube were streaked on the plate and incubated upside down in a 28°C incubator for 48 h to culture mycelium;

[0034] During cultivation, the plate culture medium is PDA medium:

[0035] Peel the potatoes, cut them into small pieces, take 200g, add 1000ml of water, heat to boiling on a heater, maintain for 20-30min, filter through 4 layers of gauze on a measuring cup while hot, discard the residue, add water to the filtrate to 1000ml, add 20g of glucose and 15g of agar, shake well, and sterilize at 121℃ for 30min;

[0036] S2. Plant pathogens confronted with Bacillus velezensis K24 plates

[0037] Cut a 5mm diameter mycelium block from the activated plant pathogen plate with a hole puncher and transfer it to the center of a new PDA plate medium. Place it in the middle of the plate and invert it at 28℃ for 48h. Pick a single colony of Bacillus Velezii K24 with a sterilized toothpick on the clean bench and inoculate it symmetrically at a position 2.5cm away from the center of the plate. Continue to culture it at 28℃ for 3-5 days. The results are as follows: Figure 1 shown.

[0038] Depend on Figure 1 It can be seen that Bacillus Velez K24 has a significant inhibitory effect on the growth of the above four plant pathogens and can be used in plant disease prevention and control.

[0039] After the fermentation liquid of Bacillus Velez K24 obtained by the above method is spray-dried, it is compounded with corn starch and maltodextrin to obtain a bacterial agent of Bacillus Velez K24 with a bacterial content of 10 billion / g, which is in powder form and is also called bacterial powder. In the following embodiments, especially in the application of bacterial agents, the bacterial agents obtained by the above method are all referred to. The 16s DNA sequence table of Bacillus Velez K24 is shown in Sequence Table 1.

[0040] Example 2

[0041] The antibacterial effects of Bacillus Velez K24, K22 and common Bacillus subtilis K61 on different diseases are compared as follows:

[0042] Culture medium: potato culture medium (PDA), culture dish, 5 mm diameter puncher, toothpick;

[0043] Bacillus Velezii K24, a strain deposited in the present invention;

[0044] Commercially available Bacillus Velezii (numbered K22);

[0045] Bacillus subtilis (No. K61)

[0046] The length and width are obtained by measuring the area. The effect of three different Bacillus and pathogen plates confronting each other is shown in the attached Figure 8 The calculation method of the inhibition rate is as follows:

[0047] Bacterial inhibition rate (%) = (pathogen longitudinal diameter - pathogen transverse diameter) / (pathogen longitudinal diameter - inoculated bacterial cake diameter) × 100%;

[0048] Table 1 Antibacterial rate of K24, K22 and K61 against different pathogens

[0049]

[0050] Table 2 Inhibition rate of three different Bacillus species K24, K22 and K61 against apple rot pathogens, etc. (%)

[0051]

[0052] The accompanying drawings corresponding to Table 2 are Figure 7 , from Table 2 and Appendix Figure 7It can be seen that the two Bacillus Velez strains (K24 and K22) have obvious inhibitory effects on six pathogens including apple rot pathogen, yam stripe smut fungus, potato gray mold pathogen, etc.; the inhibition rates of Bacillus Velez K24 and K22 against various pathogens are significantly higher than those of common Bacillus subtilis K61, and the inhibition rate of Bacillus Velez K24 is significantly higher than that of Bacillus Velez K22, which shows that the Bacillus Velez K24 provided by the present invention has better prevention effect on pathogens.

[0053] Example 3

[0054] Effect of agricultural microbial agent containing Bacillus Velez K24 on crop growth promotion

[0055] 1. Experimental Design

[0056] Based on a bacterial content of 10 billion / g, a gradient design was carried out with 500g / mu as the base amount, as shown in Table 3.

[0057] Table 3 Dosage of microbial agents in different groups

[0058] serial number CK T1 T2 T3 T4 T5 T6 Amount per mu (g / mu) 0 125 250 500 1000 2000 4000

[0059] Among them, CK was the blank control.

[0060] 2. Experimental Arrangement

[0061] 2.1 Sow cucumber seeds in a seedling tray and place them in a culture room at about 20°C for 16 hours during the day and 8 hours at night;

[0062] 2.2 When the cucumber seedlings have three leaves and one heart, transplant them to a 10×10cm pot for planting and acclimatization;

[0063] 2.3 When the cucumber seedlings grow to four to five leaves, start to apply Bacillus bernesii K24 powder (obtained by spray drying directly after fermentation culture) twice, with an interval of 7 days between each time;

[0064] 2.4 Determine the growth indicators of cucumber seedlings such as SPAD value, plant height, stem diameter, root length, and dry and fresh weight.

[0065] 3. Results Analysis

[0066] 3.1 Effects of different application rates of Bacillus velez K24 on cucumber root growth

[0067] Effects of different application rates of Bacillus Velez K24 on cucumber root growth Figure 2 As shown, Figure 2 The corresponding table is as follows:

[0068] Table 4 Effects of different application rates of Bacillus Velez K24 on cucumber root length (cm)

[0069] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5 Root length CK 23.7 28.4 29.2 27.6 29.1 27.6±1.02c T1 23.9 24.8 25.2 28.2 30.3 26.5±1.20c T2 23.6 22.9 30.6 30.2 30.2 27.5±1.74c T3 29.6 24.9 33.2 28.4 34.2 30.1±1.68bc T4 35.7 32.8 30.1 36.4 33.4 33.7±1.12ab T5 34.6 35.4 38.3 31.2 29.2 33.7±1.60ab T6 37.8 35.9 38.6 32.8 32.7 35.6±1.23a

[0070] Depend on Figure 2 It can be seen that compared with the CK group, within a certain range, with the increase in the application rate of Bacillus Velez K24 powder, the root length of the cucumber seedlings in each treatment tends to gradually increase; among them, when the per mu application rate is 1000-4000g, it has a significant promoting effect on the growth of the root length of cucumber seedlings, and the maximum increase in root length is 29.0%.

[0071] 3.2 Effects of different application rates of Bacillus Velez K24 on the stem diameter of cucumber seedlings

[0072] Effects of different application rates of Bacillus Velez K24 on the stem diameter of cucumber seedlings Figure 3 The corresponding data is shown in the following table:

[0073] Table 5 Effects of different application rates of Bacillus Velez K24 on cucumber stem diameter (mm)

[0074]

[0075]

[0076] Depend on Figure 3 It can be seen that compared with the CK group, when the application rate of Bacillus Velez K24 is within 250g / mu, increasing the application rate of Bacillus Velez K24 will promote the growth of stem diameter of cucumber seedlings, while after exceeding 250g / mu, increasing the application rate of Bacillus Velez K24 will inhibit the growth of stem diameter. When the application rate is further increased to 2000g / mu and 4000g / mu, the stem diameter of cucumber seedlings is significantly increased; that is, when 2000g and 4000g of Bacillus Velez K24 powder are applied per mu, it can significantly promote the growth of stem diameter of cucumber seedlings, and the maximum increase in stem diameter is 14.0%, indicating that Bacillus Velez K24 has the effect of promoting the growth of stem diameter of cucumber seedlings.

[0077] 3.3 Effects of different application rates of Bacillus velez K24 on the dry and fresh weight of cucumber seedlings

[0078] Effects of different application rates of Bacillus Velez K24 on the dry and fresh weight of cucumber seedlings Figure 4 and Figure 5 The corresponding data are as follows:

[0079] Table 6 Effects of different application rates of Bacillus Velez K24 on fresh weight of cucumber (g)

[0080] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5 Plant fresh weight CK 15.91 21.42 21.76 15.94 15.63 18.13±1.41b T1 18.36 15.68 17.68 15.53 18.48 17.15±0.64b T2 15.45 17.83 21.17 21.74 24.30 20.10±1.55b T3 20.24 21.19 17.77 20.79 16.60 19.32±0.90b T4 19.38 18.82 18.04 20.17 19.06 19.09±0.35b T5 23.09 18.80 23.88 25.66 25.55 23.40±1.25a T6 22.89 21.48 27.04 23.99 21.93 23.47±0.99a

[0081] Depend on Figure 4 It can be seen that when the application rate of Bacillus Velez K24 is within 1000g / mu, the fresh weight of cucumber seedlings does not change significantly with the increase of the application rate of Bacillus Velez K24, and also shows an irregular change trend. However, when the application rate of Bacillus Velez K24 increases to 2000g / mu and 4000g / mu, the fresh weight of cucumber seedlings increases significantly, and the fresh weight can be increased by up to 29.5%.

[0082] and Figure 5 The corresponding data are as follows:

[0083] Table 7 Effects of different application rates of Bacillus Velez K24 on the dry weight of cucumber (g)

[0084] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5 Plant dry weight CK 1.21 1.34 1.12 1.17 1.27 1.22±0.04d T1 1.18 1.19 1.35 1.38 1.28 1.28±0.04cd T2 1.26 1.64 1.37 1.54 1.39 1.44±0.07bc T3 1.32 1.67 1.60 1.51 1.54 1.53±0.06ab T4 1.34 1.46 1.53 1.71 1.72 1.55±0.07ab T5 1.22 1.37 1.54 1.57 1.51 1.44±0.07bc T6 1.83 1.49 1.57 1.69 1.79 1.67±0.06a

[0085] Depend on Figure 5 It can be seen that when the application rate of Bacillus Velez K24 is not less than 250g / mu, it can significantly promote the increase of dry weight of cucumber seedlings, and the maximum increase in dry weight is 36.9%. This shows that Bacillus Velez K24 has a significant promoting effect on the fresh and dry weight of cucumber seedlings.

[0086] The application of Bacillus Velez K24 powder has a certain growth-promoting effect on the root length, stem thickness, and dry and fresh weight of cucumber seedlings; especially when the application amount is 4000g / mu, the growth-promoting effect on the root length, stem thickness, and dry and fresh weight of cucumber seedlings is the most significant, and the maximum increase in root length is 29.0%, stem thickness is 14.0%, fresh weight is 29.5%, and dry weight is 36.9%. The effects of different application amounts of Bacillus Velez K24 on the growth of cucumber seedlings are shown in the figure. Figure 6 shown.

[0087] from Figure 6 It can be seen that the root length of cucumber seedlings in T3-T6 is significantly longer than that in CK group and T1-T2 group. This shows that Bacillus Velez K24 has a significant effect on promoting the root growth of cucumber seedlings.

[0088] Example 4 Control effect of different application rates of Bacillus Velezii (K24) on melon wilt (in Example 4, it is aimed at melon wilt transformed by Fusarium oxysporum)

[0089] 1. Experimental Design

[0090] The Velez agricultural microbial agent (prepared in Example 1 of the present invention, hereinafter referred to as Velez agent) has a bacterial content of 10 billion / g.

[0091] Table 8 Design of potted experiment on the resistance of melon wilt to Velez fungus

[0092]

[0093] 2. Experimental Arrangement

[0094] 2.1 Sow melon seeds in a seedling tray and place it in a culture room at about 24°C for 16 hours during the day and 8 hours at night.

[0095] 2.2 When the melon seedlings have two leaves and one bud, transplant them into 10×10 cm plastic pots according to the experimental design.

[0096] 2.3 After planting, the agricultural microbial agent Belles was applied immediately according to the experimental design, with 30 pots for each treatment.

[0097] 3. Results Analysis

[0098] 3.1 Effects of different application rates of Velez fungicide on the incidence of melons grown in diseased soil

[0099] Table 9 Relative efficacy of different application rates of Velez fungicide on melons grown in diseased soil

[0100] deal with T0 T1 T2 T3 Relative protection effect / % \ 13.5 27.2 80.2

[0101] The corresponding attached figure is as follows Fig. 9 As shown by Fig. 9 It can be seen that CK did not develop the disease, while T0-T1 had a certain degree of melon wilt disease, among which T0 had the most serious disease, reaching 92.7%; but with the increase in the amount of Velez fungus applied, the disease index gradually decreased, among which T3 had the lowest disease index of 18.3%. Compared with T0, the disease index of T1 decreased, but not significantly, and the disease indexes of T2 and T3 treatments decreased significantly. This shows that Velez fungus has a preventive and control effect on melon wilt, and with the increase in the amount of application, the control effect is also significantly enhanced; when the amount per mu reaches 2000g, the relative control effect can reach 80.2% (see the table above).

[0102] Disease index = 100 × ∑ (number of diseased leaves at each level × representative value at each level) / (total number of leaves surveyed × highest representative value);

[0103] Relative prevention effect (%) = (control disease index - treatment disease index) / (control disease index × 100);

[0104] Among them: The division of each level is as follows:

[0105] Level 0: no symptoms;

[0106] Level 1: 1 / 4-1 / 2 of the leaves of the plant show wilting symptoms, the base of the stem is asymptomatic, and the plant grows normally;

[0107] Level 2: 1 / 4-1 / 2 of the leaves of the plant show wilting symptoms, less than 1 / 2 of the stem base turns brown, and the plant wilts;

[0108] Level 3: More than 1 / 2 of the leaves of the plant show wilting symptoms, more than 1 / 2 of the stem base turns brown, and the plant is obviously dwarfed;

[0109] Level 4: The whole plant wilts and dies.

[0110] Combined with the overall growth of melon plants in each treatment (see Fig.10 ) It can be seen that the leaves and stems of melon seedlings planted in healthy soil are green and the growth is basically normal; while the melon seedlings planted in diseased soil have a certain degree of plant dwarfing, leaf yellowing and browning at the base of the stem. Among them, the dwarfing, leaf yellowing and browning at the base of the stem of the plants that were not treated with Velez fungus were the most serious, almost close to the state of dead seedlings; while the melons treated with Velez fungus had significantly reduced the degree of plant dwarfing, leaf yellowing and browning at the base of the stem, and with the increase in the amount of application, the growth of the plants gradually returned to normal; when the application rate of Velez fungus was 2000g / mu, the growth of melon seedlings planted in diseased soil was relatively close to that of melon seedlings in healthy soil.

[0111] 3.2 Effects of different application rates of Velez fungicide on SPAD values ​​of melon leaves infected with Fusarium wilt

[0112] As attached Fig.11 As shown, with the attached Fig.11 The corresponding table is as follows:

[0113] Table 10 Effects of different application rates of Velez fungicide on SPAD values ​​of melon leaves with wilt disease

[0114] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 SPAD value CK 42.2 46.0 44.3 42.3 43.7±1.8a T0 12.1 10.2 11.4 11.6 11.3±0.8e T1 14.3 16.2 17.6 15.7 16.0±1.4d T2 23.1 24.0 21.6 25.3 23.5±1.6c T3 38.1 37.6 34.0 36.4 36.5±1.8b

[0115] From Table 10 and Fig.11 It can be seen that compared with CK, the SPAD values ​​of melon seedlings in each treatment decreased significantly, among which T0 had the largest decrease, reaching 74.1%, and T3 had the smallest decrease, which was 16.4%. However, compared with T0, the SPAD values ​​of each treatment increased significantly, and with the increase in the amount of microbial agent, the SPAD values ​​gradually increased. This shows that compared with melons planted in healthy soil, the SPAD values ​​of melons planted in diseased soil were significantly reduced, that is, obvious leaf yellowing occurred; but compared with melons planted in diseased soil without flushing with Velez microbial agent, flushing with microbial agent can significantly alleviate the degree of leaf yellowing, and with the increase in the amount of flushing, the leaf yellowing phenomenon has gradually been significantly improved.

[0116] 3.3 Effects of different application rates of Velez fungicide on plant height and root length of melons with Fusarium wilt

[0117] Table 11 Effects of different application rates of Velez fungicide on plant height of melons with wilt disease (cm)

[0118] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5 Repeat 6 Plant height CK 16.1 17.8 18.9 13.6 13.8 16.2 16.1±2.1a T0 8.1 6.2 9.7 6.8 7.2 10.4 8.1±1.7c T1 9.6 7.7 8.8 9.5 7.4 7.8 8.5±1.0c T2 7.8 5.9 12.4 13.8 8.9 9.1 9.7±2.9bc T3 11.2 9.8 12.3 12.1 11.9 11.2 11.4±0.9b

[0119] Table 12 Effects of different application rates of Velez fungicide on root length of melon with wilt disease (cm)

[0120] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Root length CK 35.3 38.5 37.8 37.6 37.3±1.4a T0 16.2 18.8 17.9 17.4 17.6±1.1e T1 17.8 21.6 22.4 19.2 20.3±2.1d T2 23.4 26.7 25.8 28.1 26.0±2.0c T3 30.2 31.7 33.6 32.3 32.0±1.4b

[0121] From Tables 11, 12 and Fig.12 It can be seen that compared with CK, the plant height and root length of melon seedlings in each treatment were significantly reduced; compared with T0, with the increase of the amount of bacterial agent flushing, the plant height and root length showed an increasing trend. However, in terms of plant height, compared with T0, only the T3 treatment had a significant increase, and there was no significant difference in T1 and T2 treatments; in terms of root length, each treatment of T1-T3 was significantly higher than T0, and there were significant differences between each treatment. This shows that the plant height and root length of melons cultivated in diseased soil were significantly inhibited, and the flushing of Velez bacterial agent can alleviate this growth inhibition, and with the increase of flushing amount, the alleviating effect on the growth inhibition of melon plant height and root length gradually increased. That is, the flushing of Velez bacterial agent is conducive to alleviating the growth inhibition of melon plant height and root length caused by wilt pathogens.

[0122] 3.4 Effects of different application rates of Velez fungicide on stem diameter of melons with Fusarium wilt

[0123] Table 13 Effects of different application rates of Velez fungicide on stem diameter of melons with wilt disease (mm)

[0124] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5 Repeat 6 Stem thickness CK 4.12 4.30 3.42 4.04 4.32 3.42 3.94±0.41a T0 3.80 3.16 2.90 3.78 4.00 3.46 3.52±0.42b T1 3.74 3.88 3.70 3.84 3.60 3.70 3.74±0.10ab T2 3.60 3.74 4.08 4.02 3.78 3.46 3.78±0.24ab T3 4.00 3.90 3.94 3.68 3.68 4.04 3.87±0.16ab

[0125] From Table 13 and Fig.13 It can be seen that compared with CK, the stem diameter of each treatment decreased to a certain extent, and only T0 treatment had a significant difference with CK; compared with T0, the stem diameter of T1-T3 treatments increased to a certain extent, but not significantly. This shows that cultivation in soil with wilt disease will significantly inhibit the growth of stem diameter of melon seedlings, and flushing with Velez fungus can alleviate this inhibition to a certain extent, but the effect is not significant.

[0126] 3.5 Effects of different application rates of Velez fungicide on the dry and fresh weight of melon seedlings grown in diseased soil

[0127] 3.5.1 Impact on fresh weight

[0128] Table 14 Effect of different application rates of Velez fungicide on fresh weight of melon seedlings grown in diseased soil (g)

[0129] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5 Repeat 6 Plant fresh weight CK 7.83 7.20 7.35 9.14 7.95 9.12 8.10±0.85a T0 4.10 3.75 3.97 3.48 2.96 3.54 3.63±0.41c T1 1.91 3.66 3.74 4.44 4.91 4.83 3.92±1.12bc T2 3.84 4.62 5.12 6.83 4.85 4.06 4.89±1.07b T3 7.36 7.10 5.14 7.82 7.86 6.92 7.03±1.00a

[0130] From Table 14 and Fig.14From the fresh weight shown in the left figure, we can see that compared with CK, the fresh weight of melon plants in each treatment of T0-T2 was significantly reduced, among which T0 decreased the most, reaching 55.1%; the fresh weight of T3 treatment was also slightly reduced, but there was no significant difference with CK. Compared with T0, only the fresh weight of T1 treatment did not increase significantly, while the fresh weight of plants in T2 and T3 treatments increased significantly. This shows that diseased soil cultivation can significantly inhibit the increase of fresh weight of melon plants, but flushing with Velez bacteria can reduce the growth inhibition caused by diseased soil cultivation on the increase of plant fresh weight, and with the increase of flushing application, the growth inhibition of plant fresh weight gradually decreases; when the flushing application of Velez bacteria is 2000g / mu, the fresh weight of plants basically tends to be normal.

[0131] 3.5.2 Effect on dry weight

[0132] Table 15 Effect of different application rates of Velez fungicide on the dry weight of melon seedlings grown in diseased soil (g)

[0133] serial number Repeat 1 Repeat 2 Repeat 3 Repeat 4 Repeat 5 Repeat 6 Plant dry weight CK 0.79 0.79 0.65 0.88 0.76 0.95 0.80±0.10a T0 0.46 0.47 0.48 0.38 0.47 0.53 0.47±0.05c T1 0.42 0.43 0.48 0.58 0.61 0.64 0.53±0.10c T2 0.48 0.68 0.49 0.58 0.49 0.45 0.53±0.09c T3 0.71 0.69 0.74 0.52 0.72 0.71 0.68±0.08b

[0134] From Table 15 and Fig.14 From the right figure of dry weight, we can see that compared with CK, the dry weight of melon plants in each treatment of T0-T3 was significantly reduced, among which T0 had the largest decrease, reaching 42.1%. Compared with T0, only the dry weight of T3 treatment was significantly increased, while there was no significant difference in T1 and T2 treatments. This shows that the dry weight of melon plants cultivated in diseased soil was affected to a certain extent; flushing with Velez bacteria agent can alleviate the growth inhibition of plant dry weight; when the flushing application rate was 2000g / mu, the inhibition of plant dry weight was the smallest.

[0135] From the above melon experiment, we can see that:

[0136] (1) Melon wilt has a serious growth inhibitory effect on the SPAD value, plant height, root length, and dry and fresh weight of the plant. With the application of Velez fungicide, this growth inhibitory effect was gradually alleviated; and when the application rate reached 2000g / mu, the growth inhibition of various indicators of melon plants was minimal.

[0137] (2) Flush application of Velezella powder can prevent and control melon wilt; when the flush application rate reaches 2000g / mu, the relative prevention efficiency can reach 80.2%.

[0138] Example 5

[0139] The application effects of Bacillus Velez K24 in degrading ammonia nitrogen and COD in aquaculture water are as follows:

[0140] 5.1 Comparative strains: Bacillus Velez K24 and Bacillus subtilis K59; strains: K24 and K59 were activated and used for later use;

[0141] 5.2 Experimental purpose: To verify the effects of Velez K24 and Subtle K59 on ammonia nitrogen and COD concentrations in water bodies, and whether nitrite is generated during the experiment.

[0142] 5.3 Experimental Materials

[0143] Instruments: centrifuge, aerator, beaker, COD meter, pH meter, spectrophotometer, etc.

[0144] 5.4 Experimental design

[0145] Activation outside the system: Weigh 5g bacterial powder and 10g glucose and add them to 500ml water, aerate and activate for 3h. After the activation, measure 10ml of the activation solution and dilute it to 1L water, and measure the COD of the diluted solution as the initial value.

[0146] Degradation within the system: Add 1 / 25 of ammonia nitrogen according to the COD value of the diluted solution, activate with oxygen, and measure COD, ammonia nitrogen, and nitrite every 2 hours.

[0147] Use an aerator to aerate and maintain the dissolved oxygen at 5 mg / L or above (the dissolved oxygen in aquaculture water is generally above 5 mg / L).

[0148] 5.5 Experimental Results

[0149] The COD value changes are shown in Table 16:

[0150] Table 16 COD concentration changes (mg / L)

[0151] 0h 2h 4h 6h Control 209.2 216.7 195.6 165.5 K24 260.35 263.35 213.7 178.35 K59 246.05 269.35 237.8 186.6

[0152] As can be seen from Table 16, the COD of the blank control group, K24 and K59 groups in the water body showed a downward trend within 6 hours. The COD degradation rate of the blank control group was 20.89%, the degradation rate of the K24 treatment group was 31.50%, and the degradation rate of the K59 treatment group was 24.17%. The K24 strain had a more obvious effect on COD degradation.

[0153] The changes in ammonia nitrogen values ​​are shown in Table 17:

[0154] Table 17 Changes in ammonia nitrogen concentration (mg / L)

[0155]

[0156]

[0157] The ammonia nitrogen degradation rate of the K59 treatment group within 4 hours was 56.83%, and the degradation rate was 1.72 mg / L / h; the ammonia nitrogen degradation rate of the K24 treatment group within 4 hours was 61.76%, and the degradation rate was 1.92 mg / L / h; the degradation rate of the blank control group within 4 hours was 22.52%, and the degradation rate was 0.52 mg / L / h. The ammonia nitrogen degradation rate of the K24 strain was higher.

[0158] Example 6

[0159] (1) Test location

[0160] The bitter melon wilt disease nursery test field of the Plant Protection Institute of Shandong Agricultural University in Tai'an City, Shandong Province has a long-term incidence rate of 100% for bitter melon wilt disease in this plot since 2013.

[0161] (2) Test materials: Bitter melon, 10 billion / g of Bacillus Velezii K24 powder

[0162] (3) Experimental design

[0163] When the bitter melon seedlings were transplanted and planted on May 21, 2024, water diluted 500 times was used for the first irrigation according to the experimental design, and the second irrigation was carried out on May 28, with clean water as a control; during this period, all treatments were fertilized and watered normally.

[0164] Table 18 Bitter melon field fertilization test design

[0165] serial number CK T1 K24 usage (g / plant) 0 1 Flush times \ 2

[0166] (4) Results and analysis

[0167] On July 17, the number of healthy bitter melon plants, the number of diseased (not dead) plants, and the number of dead plants in each treatment in the experimental plots were counted, and the mortality rate, morbidity rate, relative prevention effect, etc. were calculated.

[0168] serial number Number of healthy plants Number of susceptible strains Number of dead plants Case fatality rate Incidence Relative efficacy CK 6 5 13 54.2％ 75％ \ T1 15 5 4 16.7％ 37.5％ 50％

[0169] Note: Mortality rate (%) = number of dead plants / total number of plants × 100%

[0170] Incidence rate (%) = (number of susceptible plants + number of dead plants) / total number of plants × 100%

[0171] Relative efficacy (%) = (control incidence-treatment incidence) / control incidence × 100%

[0172] From the above results, we can see that the morbidity of bitter melon plants in CK treatment reached 75%, and the mortality rate of plants was as high as 54.2%; while in T1 treatment, the morbidity of bitter melon plants was only 37.5%, and the mortality rate of plants was 16.7%; after two flushing treatments with K24, the morbidity and mortality of bitter melon wilt were greatly reduced, and the relative prevention efficiency was as high as 50%. This shows that Bacillus Velez K24 has a very obvious control effect on bitter melon wilt, and to a certain extent reflects that after Bacillus Velez is applied to the soil, it can quickly colonize and has good environmental adaptability.

Claims

1. A Bacillus Velezii K24, characterized in that The Bacillus Velez K24 is classified as Bacillus velezensis , deposited in Guangdong Microbiological Culture Collection Center with the deposit number GDMCC NO.64095.

2. Use of the Bacillus Velez K24 as claimed in claim 1 in the preparation of a product for inhibiting plant pathogens.

3. Use of Bacillus Velez K24 as claimed in claim 1 in promoting the growth of vegetable seedlings.

4. An agricultural microbial agent, characterized in that: Contains the Bacillus Velezii K24 as claimed in claim 1.

5. Use of the agricultural microbial agent as claimed in claim 4 in the preparation of a product for inhibiting plant pathogens.

6. The use according to claim 5, characterized in that The plant pathogens include at least one of apple rot pathogen, yam stripe smut fungus, potato gray mold pathogen, potato leaf mold pathogen, Fusarium graminearum, and wheat root rot helminth spore.

7. The use of an agricultural microbial agent in promoting the growth of vegetable seedlings as claimed in claim 5, characterized in that: The vegetable is cucumber or melon.

8. Use of the Bacillus Velez K24 as claimed in claim 1 in degrading ammonia nitrogen and / or COD in water bodies in aquaculture.

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