Setomelanomma tomentosum, composition containing the same, and application thereof in controlling nematodes

Abstract

The present invention relates to **Setomelanomma ciliatum**, a composition containing the same, and its application in controlling **Ditylenchus destructor**. The **Setomelanomma ciliatum** is preserved in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms, with the preservation number of CGMCC No. 40475. The composition containing **Setomelanomma ciliatum** further comprises a nematicide.

Description

Technical Field

[0001] The present invention relates to the field of biological control, and particularly to Volutella ciliate and its application in controlling sweet potato stem nematodes. Background Art

[0002] Sweet potato stem nematode disease caused by Ditylenchus destructor is one of the most serious diseases in the sweet potato production in the northern potato-growing areas of China. This nematode can parasitize and damage sweet potatoes throughout the growth period, mainly damaging the potato tubers, and also damaging the stems and seedlings. The symptoms of damaged sweet potato tubers are of the hollow-heart type, the hollow-rind type, and the mixed type. For the hollow-heart type, the nematodes in the infected sweet potato stems invade the tubers downward. The epidermis of the diseased sweet potatoes is no different from that of healthy ones, but the inside of the tubers shows dry rot with alternating brown and white colors. For the hollow-rind type, the nematodes directly invade the tubers from the soil to feed and cause damage, making the internal tissues turn brown and soft, showing blocky brown spots or small cracks. When sweet potatoes are severely diseased, the above two symptoms can occur mixedly, showing the mixed type. Sweet potato stem nematodes cause a significant reduction in the yield of sweet potatoes. In severely diseased fields, even complete crop failure may occur, causing huge losses to sweet potato production.

[0003] At present, there are limited nematicides available in the nematicide market. Some traditional nematicides such as ethoprophos, aldicarb, and cadusafos have been gradually phased out and prohibited due to their high toxicity or high residues. However, in actual production, chemical pesticides are still an important means for controlling sweet potato stem nematodes. At present, there are few microbial agent products that can be applied to sweet potato stem nematodes, and some biocontrol bacterial agents are easily affected by the soil environment and other soil microorganisms, resulting in unstable field control effects. Since nematodes damage underground secretly, the large amount and high frequency of chemical pesticides not only endanger human health and pollute the ecological environment, but also cause the resistance level of sweet potato stem nematodes to gradually increase. Ding Zhong et al. reported that the resistance multiples of sweet potato stem nematodes collected from Zhuozhou, Funing, and Lulong in Hebei Province to ethoprophos were 3.8, 1.6, and 2.1 times respectively, and the resistance multiples to aldicarb were 4.0, 3.7, and 3.5 times respectively (Ding Zhong, Peng Deliang, He Xufeng, etc.; Sensitivity of different geographical populations of sweet potato stem nematodes to different types of nematicides; Pesticides; 2007). Therefore, relying on increasing the amount of nematicides in the field to control nematode diseases can no longer solve the production problems, and there is an urgent need to discover safe and effective agents for sweet potato stem nematodes. Summary of the Invention

[0004] One aspect of the present invention provides a Volutella ciliate, which is preserved in the China General Microbiological Culture Collection Center with the preservation number CGMCC No. 40475.

[0005] Another aspect of the present invention provides a composition, which comprises the Volutella ciliate as described in one aspect of the present invention and a nematicide.

[0006] In a specific embodiment, the *Cirrenalia marginata* is the inactivated *Cirrenalia marginata*.

[0007] In a specific embodiment, the *Cirrenalia marginata* is the *Cirrenalia marginata* inactivated at 80°C to 100°C.

[0008] In a specific embodiment, the *Cirrenalia marginata* is the *Cirrenalia marginata* inactivated by treatment at 80°C to 100°C for 120 to 150 min.

[0009] In a specific embodiment, the nematicide is fosthiazate and / or fluxapyroxad.

[0010] The third aspect of the present invention provides the use of the *Cirrenalia marginata* according to the first aspect of the present invention or the composition according to any one of the second aspect of the present invention in attracting and / or controlling nematodes.

[0011] In a specific embodiment, the nematode is *Ditylenchus*.

[0012] In a specific embodiment, the nematode is *Ditylenchus destructor*.

[0013] In a specific embodiment, the *Cirrenalia marginata* according to the first aspect of the present invention or the composition according to any one of the second aspect of the present invention is applied to an area far from the roots of crops (such as sweet potatoes), for example, at a distance of 6 cm to 30 cm from the crops. This operation can achieve attracting the nematodes to an area outside the crop roots as much as possible, and when used in combination with a nematicide, it can achieve concentrated killing of the nematodes in the area outside the crop roots.

[0014] Advantages of the present invention:

[0015] The Volutella ciliata of the present invention has an attracting effect on the sweet potato stem nematode. Therefore, it can be applied to areas outside the roots of crops, so as to attract the nematodes to areas outside the roots of crops, thereby reducing the damage to crops. Further, compounding the Volutella ciliata with chemical pesticides and applying them to areas outside the roots of crops can achieve the effect of attracting the nematodes to areas outside the roots of crops and concentrating them for killing, thereby achieving the purpose of protecting crops. And compounding the Volutella ciliata with chemical pesticides can significantly reduce the use of chemical pesticides, which is beneficial to delaying the drug resistance of the sweet potato stem nematode and reducing the problem of chemical pesticide residues in crops such as sweet potatoes. In addition, since the Volutella ciliata of the present invention belongs to the endophyte of sweet potatoes and is not pathogenic to sweet potatoes, its living body can be directly applied to the field. However, since the fermented culture of the Volutella ciliata of the present invention still has an attracting effect on the sweet potato stem nematode equivalent to that before high-temperature treatment after high-temperature treatment, for environmental friendliness considerations, the Volutella ciliata can be inactivated before use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shows the phylogenetic tree constructed based on the ITS region of the isolated strain numbered SPQ7.

[0017] Figure 2 Shows the phylogenetic tree of the isolated strain numbered SPQ7 based on the SSU region.

[0018] Figure 3 Shows the attracting effects of the isolated strain numbered SPQ7 and sweet potato stems on the sweet potato stem nematode.

[0019] DEPOSIT OF MICROORGANISM

[0020] The Volutella ciliata screened in the present invention is named SPQ7. This strain is deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms, with the deposit number of CGMCC No. 40475, the deposit date of January 6, 2023, and the deposit address: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. Its systematic classification is Volutella ciliata. DETAILED DESCRIPTION OF THE INVENTION

[0021] The above content of the present invention will be further described in detail below in the form of preferred implementation cases, but it does not constitute a limitation to the present invention.

[0022] Unless otherwise specified, the reagents in the embodiments of the present invention can be purchased through commercial channels.

[0023] Example 1

[0024] Isolation and taxonomic identification of the strain

[0025] The symptomless sweet potato tubers collected were washed clean with running water and air-dried. The surfaces of the tubers were disinfected with 75% ethanol for 1 min in a sterile laminar flow hood. The epidermis of the tubers was cut off with a sterile knife and then cut into small pieces with a thickness of 5 mm. The small pieces were soaked in 75% ethanol for 3 min, and then washed 3 times with sterile water. They were transferred onto PDA medium and cultured at 25 °C for 7 days. The tip hyphae were picked and inoculated onto a new PDA plate. After multiple subculture at 25 °C, purified isolated strains were obtained. The isolated strains were numbered.

[0026] 1. Morphological identification of the isolated strains

[0027] After culturing the isolated strain numbered SPQ7 on a PDA plate for 7 days, the front side of the colony was white or milky white, velvety and nearly flat. The mycelium was usually white and arranged closely. The conidia produced were oval, with a size of 4.5 - 5.8 × 1.5 - 2.1 μm. Based on morphological observations, it was preliminarily determined to be Volutella sp.

[0028] 2. Molecular identification of the isolated strains

[0029] The fungal universal primers ITS1 (SEQ ID No.1) and ITS4 (SEQ ID No.2) were synthesized by Sangon Biotech (Shanghai) Co., Ltd. for amplifying the ITS region gene sequence of strain SPQ7, and the fungal universal primers NS1 (SEQ ID No.3) and NS6 (SEQ ID No.4) were synthesized for amplifying the SSU region gene sequence of strain SPQ7.

[0030] The genomic DNA of strain SPQ7 was extracted using the Lysis Buffer for Microorganism to Direct PCR kit (Takara). Using this DNA as a template, PCR amplification was performed with ITS1 and ITS4 as primers to obtain PCR product 1; using this DNA as a template, PCR amplification was performed with NS1 and NS6 as primers to obtain PCR product 2. PCR product 1 and PCR product 2 were respectively sent to Sangon Biotech (Shanghai) Co., Ltd. for sequencing, and the results of the sequences measured were shown as SEQ ID No.5 and SEQ ID No.6 in turn.

[0031] The ITS region gene sequence of strain SPQ7 was subjected to a homology BLAST alignment in the Genbank database. The alignment results showed that the highest similarity was with the sequence of Volutella ciliate, which was 99.27%. The SSU rDNA region gene sequence of strain SPQ7 was subjected to a homology BLAST alignment in the Genbank database. The alignment results showed that the highest similarity was with the sequence of Volutella ciliate, which was 99.47%. Sequences with relatively high similarity to the ITS region gene sequence and SSU region gene sequence of SPQ7 were downloaded from the Genbank database for constructing a phylogenetic tree. The phylogenetic tree of strain SPQ7 was constructed using the Neighbor-joining method with Mega 11.0 software, as shown in Figure 1 and Figure 2 . According to the phylogenetic tree, strain SPQ7 clustered together with Volutella ciliate and was on the same branch of the evolutionary tree.

[0032] In summary, the systematic classification of the isolated strain numbered SPQ7 is Volutella ciliate.

[0033] Strain SPQ7 was deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms. The deposit number is CGMCC No. 40475, the deposit date is January 6, 2023, and the deposit address is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. Its systematic classification is Volutella ciliate.

[0034] Example 2

[0035] Bioactivity analysis

[0036] 1. Attraction effect of strain SPQ7 on sweet potato stem nematodes

[0037] The strain Sporidesmium zonatum SPQ7 was inoculated on a PDA medium plate and cultured at 25 °C for 7 days. A mycelial disc of SPQ7 with a diameter of 1 cm was punched out from the edge mycelium. On a 1% water agar plate (9 cm), the SPQ7 mycelial disc and a PDA disc were placed opposite to each other near the edge as a control. 0.1 mL of a nematode suspension containing about 350 sweet potato stem nematodes was added dropwise to the center of the plate for a plate confrontation experiment. It was placed in a dark constant temperature incubator at 25 °C for 24 h, and repeated 4 times. After 24 h, a water agar piece (SPQ7 water agar piece) was punched out with a 2-cm-diameter puncher centered on the SPQ7 mycelial disc, and at the same time, a water agar piece (PDA water agar piece) was punched out centered on the PDA disc. The excavated SPQ7 water agar piece and PDA water agar piece were placed in petri dishes containing 30 mL of sterile water respectively, and the number of nematodes was counted separately to calculate the attraction rate of SPQ7 to nematodes. Attraction rate (%) = (number of nematodes on the SPQ7 water agar piece - number of nematodes on the PDA water agar piece) / total number of nematodes input × 100. After calculation, the attraction rate of SPQ7 to sweet potato stem nematodes was 16%.

[0038] 2. Comparison of the attraction effects of SPQ7 strain and sweet potato stems on sweet potato stem nematodes

[0039] Previous experiments have proved that the attraction of sweet potato stems to stem nematodes is significantly higher than that of sweet potato tubers, leaves and roots. Therefore, the following is a comparison of the attraction effects of SPQ7 strain and sweet potato stems on sweet potato stem nematodes.

[0040] The strain SPQ7 was inoculated on a PDA medium plate and cultured at 25 °C for 7 days. A mycelial disc of SPQ7 with a diameter of 1 cm was punched out from the edge mycelium.

[0041] On a 1% water agar plate (10 cm), the SPQ7 mycelial disc, 0.2 g of sweet potato stem (nematode-susceptible variety Jishu 98) and a 1-cm-diameter PDA disc were placed at intervals of 120° near the edge. 0.1 mL of a nematode suspension containing 350 sweet potato stem nematodes was added dropwise to the center of the plate and placed in a dark constant temperature incubator at 25 °C, and repeated 4 times. The method described in Section 1 above was used to investigate the number of nematodes attracted by the SPQ7 strain and sweet potato stems at 6 h, 9 h, 12 h, 15 h, 24 h, 30 h, 72 h and 96 h of culture and calculate the attraction rate. The results are shown in Figure 3 .

[0042] From Figure 3 the results, it can be seen that when the sweet potato stem and the SPQ7 strain are on the same water agar plate, the attraction of SPQ7 to sweet potato stem nematodes is higher than that of sweet potato stems at different time periods, and with the extension of time, the attraction of SPQ7 to sweet potato stem nematodes increases significantly. At 96 h, the attraction rate of SPQ7 can reach 6 times that of sweet potato stems.

[0043] 3. Attraction effect of heat-inactivated SPQ7 on sweet potato stem nematodes

[0044] Improved comprehensive potato liquid medium: 20 g of potato, 2 g of sucrose, 0.25 g of peptone, 0.3 g of potassium dihydrogen phosphate, 0.15 g of magnesium sulfate heptahydrate, 1 mg of VB1, 100 ml of water, pH = 7.0. Among them, after the potato is boiled and filtered, the filtrate is used to prepare the medium (refer to the preparation of PDA medium).

[0045] Inoculate the SPQ7 strain on a PDA medium plate and culture it at 25 °C for 6 d. Use a punch with a diameter of 1.5 cm to punch out the edge mycelium to obtain an SPQ7 mycelial cake with a diameter of 1.5 cm.

[0046] Take 5 pieces of SPQ7 mycelial cakes with a diameter of 1.5 cm and inoculate them into a 250 mL culture flask containing 100 mL of improved comprehensive potato liquid medium. Static culture at 25 °C for 10 d. Take the upper layer of the culture obtained, absorb the residual culture solution on the culture with filter paper, use a punch with a diameter of 1 cm to punch out several mycelial cakes to obtain viable SPQ7 mycelial cakes without inactivation. Heat the SPQ7 mycelial cakes with a diameter of 1 cm at 80 °C for 120 min to inactivate the bacteria (pick the mycelium among them and inoculate it on a PDA plate and culture it at 25 °C for 5 days, no growth), to obtain SPQ7-80 inactivated mycelial cakes. Heat the SPQ7 mycelial cakes with a diameter of 1 cm at 100 °C for 150 min to inactivate the bacteria (pick the mycelium among them and inoculate it on a PDA plate and culture it at 25 °C for 5 days, no growth), to obtain SPQ7-100 inactivated mycelial cakes.

[0047] Place the heat-inactivated bacterial cakes of SPQ7-80, SPQ7-100, the non-heat-inactivated bacterial cake of SPQ7 or 0.2 g of sweet potato stems (nematode-susceptible variety Jishu 98) near the edge of a 1% water agar plate (9 cm). Place a 1-cm diameter water agar cake (blank control) on the opposite side. Drop 0.1 mL of nematode solution containing 350 sweet potato stem nematodes at the center of the plate. Incubate in a dark constant temperature incubator at 25°C and repeat 4 times. After 24 h, use the method in the first subsection above to investigate the number of sweet potato stem nematodes attracted by the heat-inactivated bacterial cakes of SPQ7-80, SPQ7-100 and the non-heat-inactivated bacterial cake of SPQ7 and calculate the attraction rate. After calculation, the attraction rates of the heat-inactivated bacterial cakes of SPQ7-80, SPQ7-100, the non-heat-inactivated bacterial cake of SPQ7 and sweet potato stems to sweet potato stem nematodes are 12.3%, 9.1%, 15.8% and 8.9% respectively. Among them, there is no significant difference between the heat-inactivated bacterial cake of SPQ7-80 and the non-heat-inactivated bacterial cake of SPQ7; although there is a significant difference between the heat-inactivated bacterial cake of SPQ7-100 and the non-heat-inactivated bacterial cake of SPQ7, there is no significant difference in its attraction rate from that of sweet potato stems. It can be seen that after heat treatment at 80°C, the attraction ability of SPQ7 strain to sweet potato stem nematodes is equivalent to that before inactivation, that is, it also has a strong attraction ability; after heat treatment at 100°C, the attraction ability of SPQ7 strain to sweet potato stem nematodes has decreased compared with that before inactivation, but still has a good attraction effect (equivalent to that of sweet potato stems). It can be seen that the heat treatment at 100°C has a certain impact on the activity of the active substance, but within an acceptable range.

[0048] The above shows that the SPQ7 strain can produce substances that attract sweet potato stem nematodes, and these substances can withstand heat treatment at 80 to 100°C.

[0049] Example 3

[0050] Indoor and field experiments

[0051] 1. Preparation of SPQ7 culture

[0052] Modified comprehensive potato solid medium: Add 10% agar to the modified comprehensive potato liquid medium.

[0053] Wheat bran medium: 20 g of wheat bran, 9 g of wheat chaff, 6 g of sucrose, 60 mL of distilled water.

[0054] The SPQ7 strain was activated and cultured on a modified comprehensive potato solid medium plate at 25°C for 3 days. A mycelial cake of SPQ7 with a diameter of 1.5 cm was punched from the edge of the petri dish, and 5 mycelial cakes of SPQ7 were inoculated into a 300 mL culture flask containing 100 mL of modified comprehensive potato liquid medium and cultured on a shaker at 25°C and 150 rpm for 3 days. 5 mL of the culture solution containing mycelia and spores was transferred into a wheat bran medium, mixed evenly and then statically cultured at 25°C for 10 days (at this time, it could be seen that the mycelia and spores of SPQ7 had grown all over this medium), and it was mixed evenly 5 to 6 times during this period. The cultured SPQ7 culture was placed at 80°C for 2 h for inactivation treatment (after picking the mycelia and inoculating them on a PDA plate and culturing at 25°C for 5 days, there was no growth), obtaining the SPQ7 inactivated culture for use in pot experiments and field experiments.

[0055] 2. Testing the control effect of the SPQ7 inactivated culture on sweet potato stem nematodes in a seedling box

[0056] 10 sweet potato seedlings of Longshu 9 were planted on one side in a seedling box (45×45 cm), and 5 g of the SPQ7 inactivated culture was buried in the soil near the edge of the box on the other side. 3000 sweet potato stem nematodes were sprayed in the middle of the seedling box. In the seedling box used as a control treatment, 10 sweet potato seedlings of Longshu 9 were planted on the same side, and the difference was that 5 g of the non-inoculated wheat bran medium was used instead of the SPQ7 inactivated culture. After 20 days, all 10 whole sweet potato seedlings with roots were taken out, the soil on the roots was washed with clean water, and the number of nematodes in each sweet potato seedling was checked. The results showed that the average number of nematodes in each sweet potato seedling after applying the inactivated SPQ7 culture was 17±2.5, while the average number of nematodes in each sweet potato seedling in the control was 92±14.7. This result indicated that compared with the control, applying the SPQ7 inactivated culture could significantly reduce the number of sweet potato stem nematodes in sweet potato seedlings (P<0.05), indicating that the SPQ7 inactivated culture could reduce the damage of nematodes to sweet potatoes by attracting sweet potato stem nematodes to areas outside sweet potato seedlings.

[0057] 3. Testing the control effect of the SPQ7 inactivated culture on sweet potato stem nematodes in a pot experiment

[0058] The sweet potato variety was Longshu 9.

[0059] The sterilized soil was thoroughly mixed with the sweet potato stem nematode solution and filled into flower pots (diameter 15 cm, height 13 cm) so that the number of nematodes in each pot was 800. One 20 cm high sweet potato seedling was planted in the center of the flower pot as a blank control (CK).

[0060] The sterilized soil was thoroughly mixed with the sweet potato stem nematode solution and filled into flower pots (diameter 15 cm, height 13 cm) so that the number of nematodes in each pot was 800, and 5 treatments were set:

[0061] 1) SPQ7 treatment: First, bury 2 g of inactivated SPQ7 culture at one edge of the flowerpot, and then plant 1 sweet potato seedling with a height of 20 cm in the center of the flowerpot. The buried position of the SPQ7 inactivated culture is 6 to 7 cm away from the sweet potato seedling.

[0062] 2) Tiazofos treatment: First, mix 0.1 g of 10% tiazofos granules with a small amount of fine sand and then bury them in the center of the flowerpot, and then plant 1 sweet potato seedling with a height of 20 cm in the center of the flowerpot.

[0063] 3) Tiazofos + SPQ7 treatment: First, mix 2 g of inactivated SPQ7 culture with 0.1 g of 10% tiazofos granules evenly and then bury them at one edge of the flowerpot, and then plant 1 sweet potato seedling with a height of 20 cm in the center of the flowerpot. The buried position of the SPQ7 inactivated culture is 6 to 7 cm away from the sweet potato seedling.

[0064] 4) Fluopyram treatment: First, mix 20 μL of 41.7% fluopyram suspension with 50 mL of water evenly, and then pour it into the flowerpot evenly, and then plant 1 sweet potato seedling with a height of 20 cm in the center of the flowerpot.

[0065] 5) Fluopyram + SPQ7 treatment: First, mix 2 g of inactivated SPQ7 culture with 20 μL of 41.7% fluopyram suspension and bury them at one edge of the flowerpot, and then plant 1 sweet potato seedling with a height of 20 cm in the center of the flowerpot. The buried position of the SPQ7 inactivated culture is 6 to 7 cm away from the sweet potato seedling.

[0066] Each flowerpot above is used as 1 replicate, and each treatment is set with 5 replicates. During the experiment, pour equal volumes of water into each flowerpot to keep the soil moist. After 20 d, take out the whole sweet potato seedling with roots, wash the soil on the roots with clean water, and investigate the number of sweet potato stem nematodes invading in the whole sweet potato seedling. Use DPS7.05 statistical software to statistically analyze the data, and use the new multiple range method to conduct a significant analysis of the data of each treatment (P < 0.05). The results are shown in Table 1.

[0067] The results in Table 1 show that the average number of nematodes invading in each sweet potato seedling in the blank control is as high as 290. In the SPQ7 treatment, the average number of nematodes invading in each sweet potato seedling drops to 36, which is significantly lower than the number of nematodes in the sweet potato seedlings in the blank control; the average number of nematodes in each sweet potato seedling in the tiazofos treatment and the fluopyram treatment both decreased significantly compared with the blank control, while the tiazofos + SPQ7 treatment is better than the SPQ7 treatment and the tiazofos treatment, and the fluopyram + SPQ7 treatment is better than the SPQ7 treatment and the fluopyram treatment. The above results show that when the inactivated SPQ7 culture is used in combination with a nematicide, the inactivated SPQ7 culture can attract sweet potato stem nematodes to the area where the nematicide is applied by using the attracting effect of the inactivated SPQ7 culture on sweet potato stem nematodes, and the effect of centralized trapping and killing can be achieved, thereby improving the control effect of sweet potato stem nematodes.

[0068] Table 1

[0069] Treatment Number of nematodes per plant CK 290±89.5a SPQ7 36±6.8b Fosthiazate 14±0.7bc Fosthiazate + SPQ7 2±0.8de Fludioxonil 6±1.6cd Fludioxonil + SPQ7 0.5±0.5e

[0070] 4. Field experiments

[0071] Select a plot with severe occurrence of sweet potato stem nematode disease to plant sweet potatoes. The variety is Longshu 9. The ridge spacing is 80 cm, the plant spacing is 30 cm, and the planting density per mu is 3000 plants. The sweet potatoes are planted in mid-May. Except for the different treatments described below, the field is managed conventionally, and no other insecticidal agents are used during the period.

[0072] Divide the plots. Each plot has an area of 15 m 2 , and each plot is used as one replication.

[0073] Set 6 treatments:

[0074] 1) Do not apply any agents. Ridge the field for sweet potatoes, open a ditch on the ridge, water, transplant seedlings, and seal the ditch, serving as the blank control (CK);

[0075] 2) SPQ7 treatment: After ridging the field for sweet potatoes, open two ditches on the ridge. The distance between the two ditches is about 30 cm. Among them, apply the inactivated culture of SPQ7 at a rate of 6 kg / mu to one ditch, cover the soil and seal the ditch; water the other ditch, transplant seedlings, and seal the ditch.

[0076] 3) Flubendiamide-H treatment: Ridge the field for sweet potatoes, open a ditch on the ridge, water, transplant seedlings, and apply 10% flubendiamide granules at a rate of 2 kg / mu to the ditch, then seal the ditch.

[0077] 4) Flubendiamide-L treatment: Ridge the field for sweet potatoes, open a ditch on the ridge, water, transplant seedlings, and apply 10% flubendiamide granules at a rate of 1.2 kg / mu to the ditch, then seal the ditch.

[0078] 5) Flubendiamide-L + SPQ7 treatment: Ridge the field for sweet potatoes, open two ditches on the ridge. The distance between the two ditches is about 30 cm. Among them, mix 6 kg of the inactivated culture of SPQ7 and 1.2 kg of 10% flubendiamide granules evenly and apply them at a rate of 7.2 kg / mu to one ditch, cover the soil and seal the ditch; water the other ditch, transplant seedlings, and seal the ditch.

[0079] 6) Fluopyram-H treatment: Ridge the field for sweet potatoes, open a ditch on the ridge, water, transplant seedlings, and apply 41.7% fluopyram suspension at a rate of 80 mL / mu to the ditch, then seal the ditch.

[0080] 7) Fluopyram-L treatment: Ridge the field for sweet potatoes, open a ditch on the ridge, water, transplant seedlings, and apply 41.7% fluopyram suspension at a rate of 50 mL / mu to the ditch, then seal the ditch.

[0081] 8) Fluopyram - L + SPQ7 treatment: Ridges are formed in the sweet potato field. Two furrows are dug on the ridge with a furrow spacing of about 30 cm. Mix 6 kg of inactivated SPQ7 culture evenly with 50 mL of 41.7% fluopyram suspension. Apply it at a rate of 6 kg / acre of inactivated SPQ7 culture and 50 mL / acre of 41.7% fluopyram into one furrow, then cover the furrow. Water the other furrow, transplant seedlings, and cover the furrow.

[0082] Each of the above treatments is repeated 3 times. The plots are randomly grouped and arranged, and a protection row is set around the plots.

[0083] In October, harvest the sweet potatoes. When harvesting, investigate the number and weight of sweet potato tubers in each plot, record the number of diseased tubers, calculate the disease tuber rate based on the total number of tubers and the number of diseased tubers, and calculate the yield based on the weight; record the number and weight of tubers at each level according to the disease grading standard, calculate the disease index based on the number of diseased tubers and the disease level of the tubers, and calculate the control effect based on the disease index. Among them, the disease grading standard for sweet potato tubers: Grade 0, no damage by stem nematodes; Grade 1, the damaged area accounts for less than 1 / 4 of the tuber; Grade 2, the damaged area accounts for 1 / 4 - 1 / 2 of the tuber; Grade 3, the damaged area accounts for 1 / 2 - 3 / 4 of the tuber; Grade 4, the damaged area accounts for more than 3 / 4 of the tuber. Calculation methods:

[0084] Disease tuber rate (%) = (Number of diseased tubers / Total number of tubers) × 100

[0085] Disease index = ∑(Number of diseased tubers at each level × Corresponding disease level) / (Total number of tubers investigated × Highest disease level) × 100

[0086] Control effect (%) = (Disease index in the blank control area - Disease index in the treatment area) / Disease index in the blank control area × 100

[0087] The results are shown in Table 2.

[0088] The results in Table 2 show that the damage caused by sweet potato stem nematodes in the blank control area without any treatment was relatively severe, with a disease index of 35.03; the disease rate and disease index of the SPQ7 treatment were significantly reduced, and the control effect was 51.73%; the control effect of the fosthiazate-H treatment reached 81.7%, and the control effect of the fosthiazate-L treatment decreased to 56.76%, indicating that the control effect decreased with the reduction of the fosthiazate dosage; the control effect of the fosthiazate-L+SPQ7 treatment reached 87.22%, which was better than that of the SPQ7 treatment and the fosthiazate-L treatment, and was comparable to that of the fosthiazate-H treatment, indicating that the combined use of SPQ7 and fosthiazate could significantly reduce the dosage of the chemical pesticide fosthiazate, thus helping to delay the resistance of sweet potato stem nematodes and reduce the problem of fosthiazate pesticide residues in sweet potatoes and other crops. The control effect of the fluopyram-H treatment reached 74.09%, and the control effect of the fluopyram-L treatment decreased to 59.51%. Although the control effect of the fluopyram-L treatment decreased compared with that of the fluopyram-H treatment, the difference was not significant; the control effect of the fluopyram-L+SPQ7 treatment reached 79.19%. After comparison, the control effect of the fluopyram-L+SPQ7 treatment was better than that of the SPQ7 treatment and the fluopyram-L treatment, and was comparable to that of the fluopyram-H treatment, indicating that the combined use of SPQ7 and fluopyram could significantly reduce the dosage of the chemical pesticide fluopyram, thus helping to delay the resistance of sweet potato stem nematodes and reduce the problem of fluopyram pesticide residues in sweet potatoes and other crops.

[0089] Table 2

[0090] Treatment Rate of diseased potatoes (%) Disease index Control effect (%) Yield (kg / mu) CK 68.36 35.03 — 2003.53 SPQ7 treatment 49.54 16.70 51.73±3.77d 2191.33 Fosthiazate - H treatment 30.57 7.81 81.70±3.61ab 1936.23 Fosthiazate - L treatment 47.20 17.61 56.76±5.0d 2047.73 Fosthiazate - L + SPQ7 treatment 14.45 3.61 87.22±6.59a 2114.26 Fludioxonil - H treatment 43.25 10.81 74.09±2.92bc 2003.93 Fludioxonil - L treatment 53.91 15.50 59.51±3.29cd 1932.48 Fludioxonil - L + SPQ7 treatment 32.53 8.64 79.19±3.12ab 2169.16

Claims

1. A **Setomelanomma crinitum** Volutella ciliate ), which is deposited in the China General Microbiological Culture Collection Center with the deposit number of CGMCC No. 40475.

2. A composition comprising Volutella ciliate as claimed in claim 1 and a nematicide.

3. The composition according to claim 2, wherein The Volutella ciliate is the inactivated Volutella ciliate.

4. The composition according to claim 3, characterized in that, The Volutella ciliate is the Volutella ciliate inactivated after being treated at 80°C to 100°C.

5. The composition according to claim 4, wherein The Volutella ciliate is the Volutella ciliate inactivated after being treated at 80°C to 100°C for 120 to 150 min.

6. The composition according to any one of claims 2 to 5, characterized in that, The nematicide is fosthiazate and / or fluxapyroxad.

7. Use of the *Cirrenalia setosa* according to claim 1 or the composition according to any one of claims 2 to 6 in attracting and / or controlling nematodes, wherein the nematodes are *Ditylenchus destructor* ( Ditylenchus destructor ).

8. The application according to claim 7, wherein Apply the Volutella ciliate as claimed in claim 1 or the composition as claimed in any one of claims 2 to 6 in an area far from the roots of the crop.

9. The application according to claim 7, wherein Apply the Volutella ciliate as claimed in claim 1 or the composition as claimed in any one of claims 2 to 6 in an area 6 cm to 30 cm away from the crop.

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