Sweet potato long-beak-shell strain Ans and application of volatile matter thereof

Abstract

The invention belongs to the technical field of biological herbicides, particularly discloses a sweet potato long-beak-shell bacterial strain Ans and application of volatile matter of the sweet potato long-beak-shell bacterial strain Ans, and provides a sweet potato long-beak-shell bacterial strain Ans, and the classification name of the sweet potato long-beak-shell bacterial strain Ans is as follows: sweet potato long-beak-shell bacterial strain Ans, and the classification name of the sweet potato long-beak-shell bacterial strain Ans is as follows: sweet potato long-beak-shell bacterial strain Ans. The preservation number is CGMCC No.41781. Volatile organic compounds of the sweet potato long-beak-shell bacteria Ans strain provided by the invention have a very good inhibition effect on germination of weed ageratum conyzoides seeds and are safe to germination of crop rice, VOCs components of the volatile organic compounds have diversity, n-propyl acetate, isobutyl acetate or isobutyl propionate can be developed into a microbial weed sealing agent in herbicides, and the application prospect is wide. The weeding composition is used for controlling weeds in crop planting fields, especially in crop planting fields with more weeds, namely ageratum conyzoides.

Description

Technical Field

[0001] The invention belongs to the technical field of microbial herbicides, and particularly relates to application of a sweet potato long beak shell strain Ans and volatiles thereof in preventing and controlling the weed ageratum. Background Art

[0002] Ageratum Ageratum conyzoides ), commonly known as red thistle, belongs to the Asteraceae family and is an annual herb. Ageratum is native to tropical America. As a weed, it has been widely distributed throughout Africa, India, Laos, Vietnam and other places. Due to its strong reproductive ability and adaptability, it has become an invasive species in many regions of the world, posing a serious threat to agricultural production and ecological security in the invaded areas. Ageratum was introduced into my country artificially in the 19th century and is now widely distributed in the Yangtze River Basin and the areas south of it. At present, it has become a serious invasive weed in South my country. Due to its strong ecological adaptability, allelopathic effect, light competition ability, seed reproduction ability and phenotypic plasticity, it often forms a single or co-dominant community in the invaded area, inhibiting the growth of other plants, and has caused serious impacts on the tropical and subtropical ecosystems and biodiversity of the Old World. Ageratum can also affect the yield and quality of crops, and. This weed is a host to a variety of pathogens and nematodes, which can further affect crop health. On January 1, 2023, Ageratum was included in my country's list of key invasive alien species.

[0003] The widespread distribution of Ageratum in farmland has seriously affected the growth and yield of crops. The results of the preliminary survey showed that Ageratum occurs in dryland rice fields at different altitudes in Yunnan Province, with a comprehensive dominance of 13.41, second only to Digitaria, Cynanchum, Bidens pilosa and Eleocharis chinensis, and is one of the important weeds in dryland rice fields.

[0004] Microbial volatile organic compounds (MVOCs) are a group of different volatile organic compounds that may be produced by microorganisms and released into the environment. More than 1,000 MVOCs have been identified, mainly including alcohols, aldehydes, hydrocarbons, acids, ethers, esters, ketones, terpenes, organic acids, etc. Understanding the role of MVOCs in plant growth will help develop new, eco-friendly plant protection strategies and reduce the use of chemical pesticides.

[0005] Sweet potato long beak fungus ( Ceratocystis fimbriata Ellis. and Halsted) belongs to the phylum Ascomycota Ascomycota , Sclerotium Sordariomycetes , Cystaceae Microascales , Mycosporaceae Ceratocystidaceae , Longibrassium CeratocystisThe fungus is an aroma-producing fungus. Research shows that during its growth process, this fungus can produce strong fruit-like gases similar to bananas, peaches, etc., which are highly volatile. This special metabolic mechanism endows this type of fungus with various potential application values.

[0006] As an important weed in upland rice fields, Ageratum conyzoides has a significant impact on the yield and quality of upland rice. So far, there has been no report on the effect of the volatile substances of Ceratocystis fimbriata Ellis & Halst. on the germination of Ageratum conyzoides seeds, which are Compositae weeds, and rice seeds, as well as its mechanism. Summary of the Invention

[0007] In this invention, the filter paper germination method is used to study the effect of the volatile substances of Ceratocystis fimbriata Ellis & Halst. strain Ans with different culture durations on the germination of Ageratum conyzoides seeds and the safety test on the germination of rice seeds. Subsequently, the headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME / GC-MS) technique is used to determine the components of the volatile substances of Ceratocystis fimbriata Ellis & Halst. strain Ans. Finally, the Ageratum conyzoides seeds are treated with single compound components to screen out the compounds that can inhibit the germination of Ageratum conyzoides seeds. It is expected to provide a new method for the sustainable biological control of Ageratum conyzoides. Specifically, the present invention provides the following technical solutions: The present invention provides a Ceratocystis fimbriata Ellis & Halst. strain Ans, and the classification and naming of the Ans strain are: Ceratocystis fimbriata Ellis & Halst. Ceratocystis fimbriata Preservation number: CGMCC No.41781.

[0008] As an implementation method, the present invention provides a preparation method of herbicidal volatiles, and the volatiles are obtained from the Ceratocystis fimbriata Ellis & Halst. strain Ans.

[0009] Furthermore, in the preparation method of the herbicidal volatiles, when the Ceratocystis fimbriata Ellis & Halst. strain Ans is cultured in a medium until a strong aromatic odor is produced, the main components are collected by the solid-phase microextraction method.

[0010] Furthermore, in the preparation method of the herbicidal volatiles, the volatiles include n-propyl acetate, isobutyl acetate, or isobutyl propionate.

[0011] As another implementation method, the present invention provides a herbicide containing the Ceratocystis fimbriata Ellis & Halst. strain Ans.

[0012] As another implementation method, the present invention provides a herbicide containing the volatiles of Ceratocystis fimbriata Ellis & Halst. strain Ans, and the volatiles contain one or more of the compounds n-propyl acetate, isobutyl acetate, or isobutyl propionate.

[0013] As another embodiment, the present invention provides the application of the Cylindrocladium ipomoeae-batatas Ans strain, n-propyl acetate, isobutyl acetate or isobutyl propionate in controlling weeds or preparing a weed control agent.

[0014] The weeds include Ageratum conyzoides.

[0015] As another embodiment, a method for controlling weeds is to apply the herbicide to the occurrence area mainly with Ageratum conyzoides.

[0016] As another embodiment, a method for controlling Ageratum conyzoides in dry cropped paddy fields is to apply the herbicide to the dry cropped paddy fields where Ageratum conyzoides appears.

[0017] The technical effects achieved by the present invention: The 14-day fungal volatiles of the Cylindrocladium ipomoeae-batatas Ans strain provided by the present invention reduce the germination rate of Ageratum conyzoides seeds by 33.33%, shorten the root length by 90.09%, reduce the fresh weight by 66.16%, and reduce the seedling vigor index by 78.16%, while having no significant inhibitory effect on the germination of dry cropped rice seeds. HS-SPME / GC-MS detection and identification of the volatiles of the Ans-14d fungus revealed a total of 15 compounds, including esters, acids, ketones, alcohols, alkanes and alkenes. In particular, treatment with 100 μl of n-propyl acetate in the volatiles reduced the germination rate of Ageratum conyzoides seeds by 70.59% and the seedling vigor value index by 84.77% compared to the control. The volatile organic compounds of the Cylindrocladium ipomoeae-batatas Ans strain have a significant inhibitory effect on the germination of Ageratum conyzoides seeds and are safe for the germination of rice crops. Its VOCs components are diverse, and n-propyl acetate, isobutyl acetate or isobutyl propionate can be developed into a microbial source weed sealant. Description of the Drawings

[0018] Figure 1 It is a diagram of the fumigation treatment device (with a volume of about 10 L); Figure 2 It is a diagram of the placement of rice seeds (left) and Ageratum conyzoides seeds (right) in the upper tray; Figure 3 It is a diagram of the placement of the Ans fungus (left) and single compounds (right) in culture dishes; Figure 4 Diagram of the effect of the volatiles of the Cylindrocladium ipomoeae-batatas Ans strain on the germination of Ageratum conyzoides and rice seeds; Note: The lowercase letters in the figure indicate the significant differences between different treatments in Ageratum conyzoides / rice; Figure 5 Statistical analysis diagram of the effect of n-propyl acetate on the germination of Ageratum conyzoides and rice seeds; Figure 6 Statistical analysis diagram of the effect of isobutyl acetate on the germination of Ageratum conyzoides and rice seeds; Figure 7Statistical analysis chart of the effect of isobutyl propionate on the germination of Ageratum conyzoides and rice seeds. Detailed implementation mode

[0019] Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the examples regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained by purchase. The present invention will be further described in detail below with reference to examples.

[0020] In the present invention, the term "microbial source weed sealant" is a type of herbicide, which refers to a preparation that uses the microorganism itself or its metabolites as precursors and is artificially modified or synthesized to inhibit or kill weeds. These microbial preparations can be live microorganisms or metabolites with herbicidal activity produced by microorganisms.

[0021] Example 1 1 Test strain materials The test strain of Ceratocystis fimbriata Ans, classified as: Ceratocystis fimbriata Ceratocystis fimbriata ; Preserved in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms, with the preservation address at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing; Preservation date: January 20, 2025; Preservation number: CGMCC No. 41781. The source information is shown in Table 1.

[0022] Before the experiment, the strain needs to be activated: inoculate the cryopreserved Ceratocystis fimbriata strain onto the PDA medium and culture it in a constant temperature incubator at 25 °C (transfer 2 times), culture for 7 - 14 d until obvious colony morphology and strong aromatic odor are produced, and set aside for use.

[0023] Table 1 Test strains of Ceratocystis fimbriata Strain number Collection host Isolation site Collection location Ans Eucalyptus Leaves Kunming 2 Test weeds and rice seeds Ageratum conyzoides seeds were collected from Wenshan, Yunnan (longitude 103.77, latitude 23.75), and rice seeds were Dianheyou 615 (Dian Shen Dao 2017017).

[0024] Select seeds of the same size and plump grains for disinfection: soak them in 75% alcohol for 1 min, and rinse them three times with sterile water; soak them in 3% sodium hypochlorite solution for 5 - 7 min, and rinse them repeatedly with sterile water until the residual sodium hypochlorite is removed, and set aside for use.

[0025] Effect of the volatile substances of Ceratocystis fimbriata on the germination of weeds and rice seeds As Figure 1 - 3, The filter paper germination method was used to culture the seeds. The disinfected Ageratum conyzoides and rice seeds were evenly placed in a petri dish lined with a piece of filter paper (the filter paper and the petri dish had a diameter of 9 cm and were both sterilized). Each petri dish contained 20 seeds, and 5 ml of sterilized water was added. Subsequently, the petri dish containing the seeds was placed on the upper layer of a covered seedling tray. On the lower layer of the seedling tray, 6 petri dishes of Ceratocystis fimbriata cultured for 0 d (newly inoculated fungus cakes), 7 d, and 14 d were placed respectively. The control group used a blank medium, and each treatment was set with three replicates. Subsequently, the covered seedling tray was sealed with plastic wrap and placed in a light incubator (culture conditions: temperature 25°C ± 1°C, light cycle 12 h / 12 h, relative humidity 75% ± 5%). The germination and growth of rice seeds were observed and recorded every day. After 7 d, photos were taken and data such as the root length, shoot length, and fresh weight of germinated seeds were statistically analyzed, and the seed germination rate and seedling vigor index were calculated.

[0026] Germination rate = (number of germinated seeds at 7 d / number of tested seeds) * 100%; Seedling vigor index = (average root length + average shoot length) * germination rate.

[0027] Analysis of volatile organic compounds of Ceratocystis fimbriata strain by HS-SPME / GC-MS The above-mentioned *Ceratocystis fimbriata* strain was sent to Beijing Beida Zhihui Microstructure Analysis and Testing Center Co., Ltd. The volatile substances produced by the *Ceratocystis fimbriata* strain were collected and qualitatively and quantitatively determined by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME / GC-MS), and the determination method was repeated three times. The determination and analysis methods are as follows: When the *Ceratocystis fimbriata* strain was cultured until a strong aromatic odor was produced, the culture medium was chopped and placed into a solid-phase microextraction bottle. The balanced SPME fiber solid-phase microextraction head (DVB / CAR / PDMS) was inserted into the extraction bottle, the piston was pressed down to extend the fiber head, which was exposed to the upper air layer of the sample, and balanced at room temperature for 30 mins to remove residual compounds before extraction. Solid-phase microextraction was carried out at 40 °C for 1 h. After the extraction was completed, the solid-phase microextraction device adsorbed with the target mixture was inserted into the gas chromatography injection port for peak separation and detection. The chromatographic column was a DB-wax quartz capillary column (30 m × 0.25 mm × 0.25 μm), the carrier gas was high-purity helium with a flow rate of 1.0 mL min-1, the injection mode was split injection, and the split ratio was 10:1; The column oven temperature program was adopted, the initial column temperature was 40 °C, held for 5 min, heated at a heating rate of 5 °C min-1 to 200 °C, and then heated at a heating rate of 10 °C min-1 to 240 °C, held for 5 min; The mass spectrometer was operated in an EI ion source at 70 eV, the transfer line temperature was 250 °C, the ion source temperature was 230 °C, the quadrupole temperature was 150 °C, and the mass spectrometry scanning range was 33-350 amu. The relative percentage content of each component of the volatile gas substances was calculated by the area normalization method, and the GC-MS results were compared with the NIST 14.0 spectral database of the National Institute of Standards and Technology of the United States to retrieve and analyze the retention time and corresponding substance types of each volatile organic compound component.

[0028] According to the determination results of the volatile compound components of *Ceratocystis fimbriata*, single compounds were screened for subsequent seed germination experiments.

[0029] Data processing In this invention, Microsoft Excel 2016 was used to record and statistically analyze the data in real time. The data was analyzed by one-way analysis of variance using the IBM SPSS statistics 23.0 analysis software, and the LSD multiple comparison was used for significance test of differences to analyze the significant difference levels among different treatments. The Graphpad prism drawing software was used to draw the difference analysis graph.

[0030] Results 6.1 Effects of the volatiles of *Ceratocystis fimbriata* Ans strain on the seed germination of *Ageratum conyzoides* and rice The effects of the volatiles of the Ans strain with different culture durations on the seed germination of *Ageratum conyzoides* and *Dianheyou* rice are shown inFigure 4 Among them, the volatiles of the 7d and 14d bacteria have significant inhibitory effects on the seeds of Ageratum conyzoides: after treatment with the 7d bacteria, the fresh weight of the seeds of Ageratum conyzoides decreased by 26.95% (F = 18.680, p < 0.01), while the 14d bacteria reduced the germination rate, root length, fresh weight and seedling vigor index of Ageratum conyzoides by 33.33% (F = 7.739, p < 0.01), 90.09% (F = 20.233, p < 0.01), 66.16% and 78.16% (F = 8.572, p < 0.01); the 0d bacteria have no significant inhibitory or promoting effects on the germination rate of the seeds of Ageratum conyzoides. The 0d and 7d bacteria have significant promoting effects on the bud length of the seeds of Dianheyou, and the bud lengths increased by 57.56% and 40.42% respectively (F = 7.238, p < 0.05); after treatment with the 7d bacteria, the fresh weight of the seeds of Dianheyou increased by 15.40% (F = 2.055, p < 0.05), while the 14d bacteria have no significant effects on the germination rate, root length, etc. of Dianheyou.

[0031] GC-MS Analysis of Volatile Components of the Sweet Potato Longbeak Sclerotium Strain Ans From Table 2, there are a total of 24 volatile compounds in the Ans strain. Among them, the compounds with the highest peak area ratios in the volatiles of the Ans-0d bacteria are: isobutyl acetate (61.91%), ethyl acetate (25.54%), n-propyl acetate (1.74%), isobutyl propionate (1.56%), 2-methylbutyl acetate (1.27%) and formic acid (1.27%); the five compounds with the highest peak area ratios in the volatiles of the Ans-7d bacteria are: isobutyl acetate (54.83%), ethyl acetate (27.70%), formic acid (4.41%), isopentanol (2.16%), 2-methylbutyl acetate (1.90%). The five compounds with the highest peak area ratios in the volatiles of the Ans-14d bacteria are: isobutyl acetate (53.99%), ethyl acetate (35.83%), isoamyl acetate (3.76%), 2-methylbutyl acetate (3.00%), formic acid (1.05%). In the volatiles of the 0d, 7d, and 14d bacteria of Ans, the peak area ratio of isobutyl acetate is the highest, and it shows a gradually decreasing trend; while the contents of n-propyl acetate and isobutyl propionate both show a downward trend, and the peak area ratios in the volatiles of the 14d bacteria are reduced by 50% and 95.5% respectively compared with those of the 0d bacteria.

[0032] Table 2 Analysis of the Composition of Volatiles of the Sweet Potato Longbeak Sclerotium Strain Ans Example 2 Effects of 3 Single Compounds on the Germination of Weed and Rice Seeds n-Propyl acetate (density 0.888 g / ml, purity 99%, Shanghai Macklin Biochemical Co., Ltd.), isobutyl acetate (density 0.873 g / ml, purity 99%, Shanghai Macklin Biochemical Co., Ltd.), isobutyl propionate (density 0.87 g / ml, purity ≥98%, Shanghai Aladdin Biochemical Technology Co., Ltd.). Appropriate volumes of the above single compounds were respectively dissolved in 1 ml of DMSO to prepare 5 concentration gradients, among which: n-propyl acetate (20 μl, 40 μl, 60 μl, 80 μl, 100 μl), isobutyl acetate and isobutyl propionate (100 μl, 200 μl, 300 μl, 400 μl, 500 μl). The method of the seed germination test refers to Example 1. 1 ml of the single compound with different concentrations was respectively dropped on the filter paper in the lower culture dish of each seedling tray (V≈10 L), and 1 ml of DMSO was used in the control group ( Figure 1 - 3 ). Each treatment was set with three replicates.

[0033] The seedling trays were sealed with plastic wrap and placed in a light incubator (culture conditions: temperature 25°C ± 1°C, light cycle 12 h / 12 h, relative humidity 75% ± 5%). The germination and growth of Ageratum conyzoides and rice seeds were observed every day. After 7 days, the root length, shoot length and fresh weight of the germinated seeds of Ageratum conyzoides and rice were measured and recorded, and the seed germination rate and seedling vigor index were calculated (see Example 1).

[0034] Effect of n-Propyl Acetate on the Germination of Ageratum conyzoides Seeds and Rice Seeds As Figure 5 shown, n-propyl acetate has a significant inhibitory effect on the germination of Ageratum conyzoides seeds, and the inhibitory effect increases with the increase of the concentration of n-propyl acetate. Among them, the germination rate of Ageratum conyzoides seeds decreased significantly, which were respectively 21.57%, 31.37%, 39.22%, 35.29% and 70.59% lower than that of the control (F = 30.97, p < 0.01); the root length of Ageratum conyzoides decreased significantly, which were respectively 15.00%, 37.14%, 57.14%, 48.09% and 55.95% less than that of the control (F = 24.725, p < 0.01); except for the 40 μl treatment, the shoot length of Ageratum conyzoides decreased significantly, which were respectively 21.23%, 19.07%, 31.66% and 38.49% less than that of the control (F = 7.393, p < 0.01); the fresh weight of the young shoots of Ageratum conyzoides decreased significantly, which were respectively 18.83%, 24.68%, 38.53%, 44.37% and 53.68% less than that of the control (F = 20.537, p<0.01); The vigor index (SVI) of Ageratum conyzoides seedlings decreased significantly, by 34.50%, 50.66%, 64.97%, 62.07% and 84.77% respectively compared with the control (F = 50.816, p <0.01).

[0035] n-Propyl acetate had no significant effect on the germination rate, root length, fresh weight of young shoots and vigor index of rice seeds, and the 80ul treatment had a significant promoting effect on the shoot length of rice, with the shoot length increasing by 29% compared with the control.

[0036] Effects of isobutyl acetate on the germination of Ageratum conyzoides seeds and rice seeds As Figure 6 shown, isobutyl acetate had a significant inhibitory effect on Ageratum conyzoides seeds, and the inhibitory effect increased with the increase of the concentration of isobutyl acetate. Among them, the germination rate of Ageratum conyzoides seeds decreased significantly under the treatments of 100ul, 300ul, 400ul and 500ul, by 29.41%, 39.22%, 23.53% and 27.45% respectively compared with the control (F = 5.123, p <0.05); The root length of Ageratum conyzoides decreased significantly, by 26.66%, 28.81%, 43.34%, 44.29% and 61.66% respectively compared with the control (F = 8.007, p <0.01); The 100ul treatment could significantly increase the shoot length of Ageratum conyzoides, by 19.42% compared with the control. The shoot length decreased significantly under the treatments of 400ul and 500ul, by 33.45% and 28.06% respectively compared with the control (F = 16.071, p <0.01). The effects of the 200ul and 300ul treatments on the shoot length were not significant; The fresh weight of young shoots of Ageratum conyzoides decreased significantly only under the 400μl treatment, by 29.44% compared with the control (F = 3.065, p <0.05), and there was no significant difference from the control under other treatments; The vigor index (SVI) of Ageratum conyzoides seedlings decreased significantly, by 35.00%, 33.08%, 58.18%, 54.39% and 62.14% respectively compared with the control (F = 22.199, p <0.01).

[0037] Isobutyl acetate had no significant effect on the germination rate, root length, shoot length, vigor index of seedlings and fresh weight of young shoots of rice seeds.

[0038] Effects of isobutyl propionate on the germination of Ageratum conyzoides seeds As Figure 7As shown in the figure, isobutyl propionate has a significant inhibitory effect on the germination of Ageratum conyzoides seeds, and the inhibitory effect increases with the increase of the concentration of isobutyl propionate. Among them, the germination rate of Ageratum conyzoides seeds decreased significantly under the treatments of 200ul, 300ul, 400ul and 500ul, and decreased by 72.55%, 78.43%, 80.39% and 74.51% respectively compared with the control (F = 39.093, p < 0.01); the root length of Ageratum conyzoides was significantly shortened, and decreased by 43.34%, 85.95%, 84.05%, 91.43% and 85.00% respectively compared with the control (F = 49.608, p < 0.01); the shoot length of Ageratum conyzoides was significantly shortened under the treatments of 200ul, 300ul, 400ul and 500ul, and decreased by 49.28%, 43.53%, 43.53% and 37.06% respectively compared with the control (F = 28.845, p < 0.01); the fresh weight of Ageratum conyzoides seedlings decreased significantly, and decreased by 22.73%, 61.47%, 63.20%, 66.67% and 56.06% respectively compared with the control (F = 21.516, p < 0.01); the vigor index (SVI) of Ageratum conyzoides seedlings decreased significantly, and decreased by 33.30%, 91.97%, 94.00%, 94.68% and 91.04% respectively compared with the control (F = 81.624, p < 0.01).

[0039] The treatment of isobutyl propionate had no significant effect on the shoot length of rice seeds.

[0040] Previous studies have shown that microbial volatile organic compounds have positive / negative regulation on plant growth. The research results of this invention show that the volatiles of Ans-14d bacteria have a significant inhibitory effect on the germination of Ageratum conyzoides seeds. Among its volatiles, n-propyl acetate, isobutyl acetate and isobutyl propionate all show a strong inhibitory effect on the germination of Ageratum conyzoides seeds and have no significant effect on the germination of rice seeds. It can be developed into a microbial source weed sealant (or microbial source herbicide) for controlling the weed Ageratum conyzoides, especially for controlling Ageratum conyzoides in dry-cultivated rice fields. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A sweet potato long beak fungus Ans strain, characterized in that The Ans strain is classified and named as: Ceratocystis fimbriata ; Deposit number: CGMCC No.41781.

2. A method for preparing herbicidal volatiles, characterized in that: The volatiles are prepared from the Echinops spp. Ans strain of claim 1.

3. The method for preparing the herbicidal volatiles according to claim 2, characterized in that: The sweet potato long-beaked phycoerythrocytes Ans strain described in claim 1 is cultured in a culture medium until a strong aromatic smell is produced, and the main components thereof are collected by solid phase microextraction.

4. The method for preparing the herbicidal volatiles according to claim 2, characterized in that: The volatiles include n-propyl acetate, isobutyl acetate or isobutyl propionate.

5. A herbicide, characterized in that: The herbicide contains the sweet potato long beaked fungus Ans strain according to claim 1.

6. A herbicide, characterized in that: The herbicide contains volatiles of the sweet potato long beaked fungus Ans strain, and the volatiles contain one or more of the compounds n-propyl acetate, isobutyl acetate or isobutyl propionate.

7. Use of the Ans strain of Ipomoea batatas, n-propyl acetate, isobutyl acetate or isobutyl propionate according to claim 1 in controlling weeds or preparing a weed control agent.

8. The use according to claim 7, characterized in that: The weeds include ageratum.

9. A method for controlling weeds, characterized in that: The herbicide according to claim 5 or 6 is applied to a site where the weed Ageratum mainly occurs.

10. A method for controlling ageratum weeds in dry rice fields, characterized in that: The herbicide according to claim 5 or 6 is applied to a dry rice field where the weed Ageratum is present.

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