Endophytic fungus Ns399 and application thereof

Abstract

The invention discloses an endophytic fungus Ns399 and application thereof, and belongs to the technical field of microorganisms. The endophytic fungus Ns399 is classified and named as Nodulisporidium sp. Ns399, the endophytic fungus Ns399 is preserved in the China Center for Type Culture Collection, and the preservation number is CCTCC NO: M 20252459. The endophytic fungi Ns399 and rice are co-cultured, so that the endophytic fungi Ns399 is colonized in root tissues of the rice, the salt tolerance of rice plants, especially in the seedling stage, can be enhanced, and the growth of the plants is promoted. Therefore, the endophytic fungus Ns399 has popularization and application values in the aspects of guaranteeing plant health and improving rice seedling stage growth.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, specifically to an endophytic fungus. Nodulisporium sp. Ns399 and its application in improving rice's tolerance to salt stress and promoting rice growth. Background Technology

[0002] Rice ( Oryza sativa Rice (L.) is an annual aquatic herbaceous plant belonging to the Poaceae family and is one of the most important food crops for humans. Rice is subject to various abiotic stresses during its growth, such as drought, salinity, extreme temperatures, and heavy metal pollution, which severely affect its growth and yield. Specifically, soil salinization has become a major abiotic stress factor restricting agricultural production. High-salt environments affect rice growth, leading to root damage and impaired nutrient absorption. These environmental stresses severely inhibit plant growth, affect crop yield and quality, and threaten the sustainable development of agriculture.

[0003] Endophytic fungi, as a class of beneficial microorganisms for plants, are receiving increasing attention for their role in enhancing plant resilience to abiotic stresses such as salinity and alkalinity. These fungi can colonize plants without causing disease and promote plant growth through various mechanisms, thereby improving their adaptability to adverse conditions.

[0004] For example, in terms of alleviating salt and alkali stress, studies have shown that Trichoderma ( Trichoderma koningii By releasing volatile organic compounds, it significantly reduces hydrogen peroxide accumulation and cell necrosis in plants under salt stress, thereby enhancing their antioxidant capacity (Jalali F, et al . Volatile organic compounds of some Trichoderma spp.increasegrowth and induce salt tolerance in Arabidopsis thaliana . Fungal Ecology , 2017, 29: 67-75.). Patent document CN 113308379 A discloses Trichoderma longifolia ( Trichoderma longibrachiatum HXF-10 has the ability to solubilize phosphorus and tolerate salt. Soaking wheat seeds in HXF-10 bacterial solution before sowing and keeping them moist can effectively improve the salt stress resistance of wheat seeds in high saline-alkali land during germination.

[0005] Given the broad application potential of endophytic fungi in promoting plant growth under multiple stresses, exploring a richer resource library of endophytic fungal strains and utilizing their interactions with crops to synergistically enhance crop resistance to stresses such as salinity and alkalinity, thereby ensuring food security, is of great significance for promoting green agriculture and sustainable land use.

[0006] genus Polysporus ( Nodulisporium (Ascomycota) is a fungal microorganism belonging to the phylum Ascomycota. It has been found in endophytic fungal communities of plants such as ancient tea gardens in Yunnan and rabbiteye blueberries. Studies have shown that its metabolites include alkaloid compounds and antibacterial active substances, indicating its potential for development into biopesticides. However, the role of strains of this genus in enhancing crop resistance to adverse conditions such as salinity and alkalinity has not yet been reported. Summary of the Invention

[0007] The purpose of this invention is to provide an endophytic fungal strain that can promote rice growth and improve its tolerance to salt stress, so as to solve the problem of limited rice growth in saline-alkali soil.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: This invention isolated a strain belonging to the genus Arthrospora from the fern *Pteris vittata*. Nodulisporium The novel strain has the following main biological characteristics: colonies reach a diameter of 6 cm after 5 days of growth on PDA plates at 25°C; aerial hyphae are underdeveloped, creeping along the culture medium surface, with off-white colonies and transparent or white hyphae, 1.0-2.5 μm wide; it does not produce sporulations; and in liquid PDB medium, the hyphae turn dark brown after 5 days of cultivation at 25°C. The ITS sequence of this endophytic fungus is shown in SEQ ID NO.1. Phylogenetic tree construction identified this strain as belonging to the kingdom Fungi. Fungi Ascomycota Ascomycota Fibromycetes Sordariomycetes , Charcoalales Xylariales , Carbonaceae Xylariaceae Arthrospora Nodulisporium Therefore, it is named: Nodulisporium sp. Ns399 was deposited on November 6, 2025 at the China Center for Type Culture Collection (CCTCC), Wuhan University, Wuhan, China, with accession number CCTCC NO: M 20252459.

[0009] Furthermore, the culture conditions for the endophytic fungus strain Ns399 were as follows: the endophytic fungus Ns399 was inoculated into PDA solid medium and cultured in the dark at 22-25℃ for 5-10 days.

[0010] This invention also provides a formulation of endophytic fungus Ns399, which is prepared into a solid microbial fertilizer. The preparation method includes: inoculating the endophytic fungus Ns399 into a liquid fermentation medium, culturing to obtain a fermentation broth, then inoculating the fermentation broth onto sterile barley grains, and culturing in the dark until the mycelium grows and covers the barley grains, thereby obtaining Ns399 solid microbial fertilizer; the liquid fermentation medium is composed of 5 g potato starch, 10 g peptone, and 15 g glucose per 1000 mL.

[0011] Furthermore, the fermentation broth was mixed with sterile barley grains at a ratio of 150 mL: 200 g, and cultured in the dark at 25°C until the mycelium grew and covered the barley grains, thus obtaining Ns399 solid microbial fertilizer.

[0012] The solid microbial fertilizer can be applied as follows: the solid microbial fertilizer is mixed into the seedling substrate, and the germinated crop seeds are sown in the seedling substrate containing endophytic fungus Ns399. During the seedling process, endophytic fungus Ns399 colonizes the roots of the seedlings.

[0013] This invention has found that... Nodulisporium When sp. Ns399 is colonized in the root tissue of rice, it can significantly promote the growth of rice seedlings. The study also found that... Nodulisporium When sp. Ns399 is colonized in the root tissue of rice, it can significantly promote the growth of rice seedlings in salt-stressed soil and enhance the tolerance of rice seedlings to salt stress.

[0014] Therefore, the present invention provides the application of the endophytic fungus Ns399 in promoting rice growth and improving rice's tolerance to salt stress.

[0015] The application includes colonizing the endophytic fungus Ns399 into the root tissue of rice.

[0016] Furthermore, the application includes: co-culturing rice seeds with the endophytic fungus Ns399 after germination, allowing it to colonize the roots of rice seedlings, thereby improving the salt stress tolerance of rice seedlings.

[0017] Furthermore, the application includes: preparing endophytic fungus Ns399 into solid microbial fertilizer, mixing it into a seedling substrate to obtain a mixed substrate, and sowing rice seeds in the mixed substrate after germination to obtain rice seedlings.

[0018] When the Ns399 strain was co-cultured with rice seedlings in the form of microbial fertilizer, and then colonized at the roots of the rice seedlings, it could significantly promote the growth of rice seedlings under both no-stress and salt-stress conditions.

[0019] Preferably, the co-culture conditions are: 22-25℃, 16 h light exposure, and 8 h dark incubation.

[0020] The present invention also provides the application of the endophytic fungus Ns399 in promoting rice growth, the application including: colonizing the endophytic fungus Ns399 in rice root tissue.

[0021] This invention demonstrates that the interaction between the endophytic fungus Ns399 and rice seedlings can significantly improve the growth performance of rice seedlings. Specifically, the indicators of rice growth include plant fresh weight, plant height, chlorophyll content, and leaf width.

[0022] The beneficial effects of this invention are as follows: This invention provides a novel strain of the genus Arthrospora ( Nodulisporium Endophytic fungi, through interaction with rice, can significantly promote rice growth under both stress-free and salt-stress conditions. Co-culturing the endophytic fungus Ns399 with rice, allowing it to colonize the rice root tissue, can enhance the rice plant's tolerance to salt stress, especially during the seedling stage, and promote plant growth. Therefore, the endophytic fungus Ns399 has significant application value in ensuring plant health and improving rice seedling growth. Attached Figure Description

[0023] Figure 1 Phylogenetic tree of strain Ns399.

[0024] Figure 2 This is a test of the salt tolerance of strain Ns399 on plates in Example 2.

[0025] Figure 3 This shows the colonization of strain Ns399 on rice roots.

[0026] Figure 4 This section describes the effect of strain Ns399 on rice growth in Example 4. A represents the overall performance of potted plants; B represents the performance of individual plants; and C and D represent the effects of strain Ns399 on rice seedling fresh weight, plant height, chlorophyll content, and leaf width, respectively. The bar chart represents the mean ± standard deviation, n=9. Significant differences (using Tukey's method for multiple comparisons, one-way ANOVA): *** represents... P <0.001, **** represents P <0.0001. Where CK represents the control group without Ns399 inoculation, and Ns399 represents the experimental group inoculated with strain Ns399.

[0027] Figure 5 This section describes the effect of strain Ns399 on salt tolerance in rice in Example 5. A represents the overall performance of potted plants; B represents the performance of individual plants; and C and D represent the effects of strain Ns399 on seedling height, leaf width, chlorophyll content, and fresh weight under 0.2 mol / L salt stress, respectively. The bar chart represents the mean ± standard deviation, n=9. Significant differences (using Tukey's method with multiple comparisons, one-way ANOVA): * indicates... P <0.05, ** represents P <0.01, *** represents P <0.001. Where CK represents the control group without Ns399 inoculation, and Ns399 represents the experimental group inoculated with strain Ns399. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0030] The culture media involved in the following examples: MEA medium: Each liter contains 20g of malt extract and 15g of agar powder, autoclaved at 121℃ for 20 min.

[0031] Potato glucose agar (PDA) medium: 20 g glucose, 200 g potato, and 15 g agar per liter. Weigh the required amount of potato according to the volume of the medium to be prepared, boil in water, mash and dissolve, filter, add glucose and agar, and autoclave at 121°C for 20 min.

[0032] PDB liquid fermentation medium: each liter contains 5 g potato extract powder, 10 g peptone, and 15 g glucose, autoclaved at 121°C for 20 min.

[0033] Example 1: Isolation, purification and identification of endophytic fungus strain Ns399 I. Strains Isolation and Purification (1) Gently rinse the root zone of the fern plant collected from Yinchuan with water, soak it in 75% ethanol for 10 minutes, and then rinse it twice with sterile water. (2) Soak in 1.5% sodium hypochlorite for 3-5 minutes, rinse with sterile distilled water 3-5 times, and cut the plant roots into root segments about 5 mm long; (3) The root segments were transferred to MEA medium and cultured in the dark at 25°C; (4) The fungi that grow out are promptly transferred to PDA medium. After several generations of inoculation, purified fungi are obtained and numbered Ns399. (5) The purified fungi were preserved on PDA slant and sealed with liquid paraffin.

[0034] II. Strain Identification 1. Morphological identification After isolation and purification, strain Ns399 was inoculated onto PDA medium and cultured at 25°C for 7 days. A small amount of bacterial cells was picked up with a needle, prepared onto a glass slide, and observed and measured under a microscope.

[0035] Its morphological characteristics are as follows: strain Ns399 grows rapidly on PDA plates, with a colony diameter of 6 cm after 5 days of growth at 25℃; aerial hyphae are underdeveloped, creeping and adhering to the surface of the culture medium, with a white colony and transparent or white hyphae, 1.0-2.5 μm wide; it does not produce spores; after 5 days of culture in liquid PDB medium at 25℃, the hyphae turn dark brown.

[0036] 2. Molecular identification (1) DNA extraction ① After culturing Ns399 strain on PDA plates at 25℃ for 5 days, scrape the mycelium from the plates with a toothpick and put it into a sterilized centrifuge tube containing 300 μL of extraction buffer (1 M KCl, 100 mM Tris HCl, 10 mM EDTA, pH=8.0); ② Grind with an electric grinder and shake vigorously for 2 minutes; ③ Centrifuge at 10000 rpm for 10 min; ④ Aspirate the supernatant and transfer it to another new centrifuge tube, discarding the precipitate; ⑤ Add an equal volume of isopropanol (analytical grade) to the supernatant, gently invert and mix several times, then centrifuge at 12000 rpm for 10 min to precipitate nucleic acids; ⑥ Gently pour off the supernatant and invert the centrifuge tube containing the precipitate onto absorbent paper to drain the water; ⑦ Add 300 μL of 70% ethanol, gently invert and mix several times, then centrifuge at 12000 rpm for 2 min; ⑧ Gently pour off the supernatant and repeat step ⑦ once; ⑨ Invert the centrifuge tubes onto absorbent paper to drain excess water, and place them at 37°C for 15 minutes to allow the ethanol to evaporate completely; ⑩ The precipitate was resuspended in 50 μL ddH2O to obtain Ns399 genomic DNA at a concentration of 30 ng / μL.

[0037] (2) PCR amplification of fungal ITS rDNA gene PCR amplification was performed in a 50 μL reaction system containing: 2 μM each of forward and reverse primers, 200 μM dNTPs, 1.5 mM MgCl2, 5 μL 10×PCR buffer, 2 μL template DNA, and 2 U Taq enzyme.

[0038] The upstream primer ITS1 sequence is: 5'-TCCGTAGGTGAACCTGCGG-3'. The downstream primer ITS4 sequence is: 5'-TCCTCCGCTTATTGATATGC-3'.

[0039] PCR amplification was performed on a Lange MG96G PCR instrument. Reaction conditions: 94℃ pre-denaturation for 2 min, followed by 35 cycles of: 94℃ denaturation for 30 sec, 55℃ annealing for 40 sec, 72℃ extension for 1 min, and a final extension at 72℃ for 10 min.

[0040] (3) Recovery and purification of PCR products After the PCR reaction was completed, the PCR products were detected by 1% agarose gel electrophoresis and then purified using the DNA gel purification kit from ASICS Biotech.

[0041] (4) Gene sequencing and sequence analysis The purified and recovered target DNA fragment, after electrophoresis detection, was sent to the Hangzhou sequencing department of Youkang Biotechnology Co., Ltd. for sequencing. After rigorous verification, the sequencing results yielded a DNA fragment sequence of 986 bp, as shown in SEQ ID NO.1.

[0042] On the NCBI website, the determined nucleotide sequence was searched and compared with homologous or similar nucleotide sequences in the GenBank database using BLAST. After BLAST alignment, the sequence showed 100% coverage and 99.19% similarity to accession number LC504946.1. This sequence originates from the genus *Arthrospora* (…). Nodulisporium The ITS rDNA sequence of sp. Rt7-1.

[0043] Phylogenetic tree ( Figure 1 The results showed that Ns399 is related to Arthrosporium ( ). Nodulisporium ), genus *Amanita* ( Annulohypoxylon The strain is closely related to Arthrospora. Based on the combined results of nucleotide sequence and phylogenetic tree analysis, Ns399 is considered to be a strain belonging to the genus Arthrospora (…). Nodulisporium ) strains.

[0044] The above molecular and morphological identification results indicate that this strain belongs to the kingdom Fungi ( ). Fungi Ascomycota ( Ascomycota ), class of fecal scabies ( Sordariomycetes ), Charcoalales ( Xylariales ), Chalcoceraceae ( Xylariaceae Arthrospora ( ) Nodulisporium Therefore, it is named: Nodulisporium sp.Ns399 was deposited at the China Center for Type Culture Collection (CCTCC), Wuhan University, Wuhan, China, on November 6, 2025, with accession number CCTCC M 20252459. The collection was identified as viable on November 13, 2025.

[0045] Example 2: Tolerance of endophytic fungus Ns399 to salt stress 1. Activation culture of bacterial strains The Ns399 strain preserved on the slant was inoculated onto potato dextrose agar (PDA) solid medium for activation culture, and cultured in the dark at 25°C for 5 days for later use.

[0046] 2. Testing the tolerance of strain Ns399 to salt concentration gradients. The sodium chloride concentrations in the PDA medium were 0 mol / L, 0.2 mol / L, and 0.4 mol / L, respectively. Strain Ns399 cells were inoculated onto PDA media with different salt concentration gradients and cultured at 25°C in the dark for 5 days.

[0047] 3. Results Analysis like Figure 2 As shown, different salt concentrations caused significant differences in the colony morphology of Ns399. Under salt-free stress, the colonies were white with white aerial hyphae. As the salt concentration increased, the colonies gradually turned whiter and the colony diameter gradually decreased. When the salt concentration was 0.2 mol / L, the colony diameter decreased, but the color did not change. When the salt concentration was 0.4 mol / L, colony growth was inhibited, and the colony diameter decreased significantly.

[0048] Example 3: Colonization of endophytic fungus Ns399 in rice roots 1. Activation culture of bacterial strains The Ns399 strain preserved on the slant was inoculated onto potato dextrose agar (PDA) solid medium for activation culture, and cultured in the dark at 25°C for 7 days for later use.

[0049] 2. Co-culture of Ns399 strain with rice After removing the husks from rice seeds, shriveled, dry, and insect-infested grains were removed. Healthy rice seeds were disinfected with 75% alcohol for 5 minutes, followed by 1% NaClO for 20 minutes. The seeds were then rinsed five times with sterile water before use. The disinfected seeds were transferred to half MS medium using sterile forceps, sealed with sealing film, and incubated at 25°C for germination (16 h light / 8 h dark). After 3-4 days, the emerging seeds were inoculated into square dishes containing half MS + PDB medium, with 8-9 seeds per dish. For the treatment group, 6-7 Ns399 mycelial discs (5 mm in diameter) were inoculated under the seeds, while the control group received half MS + PDB medium with sterile mycelial discs. Each treatment was repeated in triplicate, incubated at 25°C for 16 h light / 8 h dark for 15-20 days until the three-leaf stage.

[0050] 1 / 2 MS+PDB medium: per 1000 mL contains 0.5 g MES, 2.2 g MS Salt, 5 g sucrose, 8 g agar powder, 17.5 g PDB, pH 5.7, autoclaved at 121℃ for 20 min.

[0051] Trypan blue staining of rice roots The rice roots of the control group and the treatment group were cleaned, dried, and cut into 1 cm sections. The rice roots were stained with trypan blue and then observed under an inverted fluorescence microscope.

[0052] 4. Results Analysis Colonization status such as Figure 3 As shown, a small amount of uniform blue dye residue was found in the intercellular spaces or tissue edges of the rice root cells in the control group, but it did not enter the root cells. In contrast, the rice root cells in the treatment group had filamentous, septate, and network-distributed blue hyphae structures on the surface and inside, indicating that Ns399 hyphae could invade the root cells.

[0053] Example 4: Co-cultivation of Ns399 microbial fertilizer and potted rice seedlings under no-stress conditions 1. Activation culture of bacterial strains The Ns399 strain preserved on the slant was inoculated onto potato dextrose agar (PDA) solid medium for activation culture, and cultured in the dark at 25°C for 5 days for later use.

[0054] 2. Preparation of Ns399 solid microbial fertilizer Endophytic fungal Ns399 mycelial blocks (0.5 cm in diameter) cultured for 5 days were placed in PDB liquid fermentation medium (containing 5 g potato extract, 10 g peptone, and 15 g glucose per 1000 mL) for fermentation at 25°C and 150 rpm for 5 days. The fermentation liquid was then inoculated onto sterilized barley grains (150 mL / 200 g inoculation amount) and incubated in the dark for 15 days until the barley grains were fully covered with mycelium, yielding Ns399 solid microbial fertilizer.

[0055] 3. Co-cultivation of Ns399 microbial fertilizer with potted rice seedlings (1) Application of solid microbial fertilizer: Mix the fermented solid microbial fertilizer with the seedling substrate and use it as new substrate soil for rice pot cultivation. Soak rice seeds (Zhejiang Jing 99) in 70% alcohol for 15 minutes to disinfect the surface, rinse them 3 times with running water, and then place them in a 37℃ dark constant temperature incubator to germinate for 2 days. When the seeds show white sprouts, sow them evenly in the pots.

[0056] (2) Rice seedling pot cultivation: Rice was cultivated in pots at 25℃ for 16 h of light and 8 h of darkness for a total of 14 days. The growth was observed and recorded, and various growth indicators were statistically analyzed.

[0057] 4. Results Analysis like Figure 4 As shown, under pot cultivation conditions and without stress, plants inoculated with strain Ns399 showed significantly higher fresh weight, plant height, chlorophyll content, and leaf width than the control group. Both the overall plant performance and individual plant performance indicated that plants inoculated with strain Ns399 exhibited better growth than the uninoculated group.

[0058] Example 5: Co-cultivation of Ns399 microbial fertilizer and potted rice seedlings under salt stress 1. Activation culture of bacterial strains The Ns399 strain preserved on the slant was inoculated onto potato dextrose agar (PDA) solid medium for activation culture, and cultured in the dark at 25°C for 5 days for later use.

[0059] 2. Preparation of Ns399 solid microbial fertilizer Endophytic fungal Ns399 mycelial blocks (0.5 cm in diameter) cultured for 5 days were placed in PDB liquid fermentation medium (containing 5 g potato extract, 10 g peptone, and 15 g glucose per 1000 mL) for fermentation (25℃, 150 rpm, 5 days). The fermentation liquid was then inoculated onto sterilized barley grains (150 mL / 200 g inoculation amount) and incubated in the dark for 15 days until the barley grains were fully covered with mycelium, yielding Ns399 solid microbial fertilizer.

[0060] 3. Co-cultivation of Ns399 microbial fertilizer with potted rice seedlings (1) Application of solid microbial fertilizer: Mix the fermented solid microbial fertilizer with the seedling substrate and use it as new substrate soil for rice pot cultivation. Soak rice seeds (Zhejiang Jing 99) in 70% alcohol for 15 minutes to disinfect the surface, rinse them 3 times with running water, and then place them in a 37℃ dark constant temperature incubator to germinate for 2 days. When the seeds show white sprouts, sow them evenly in the pots.

[0061] (2) Rice seedling pot culture: Rice was cultured in pots at 25℃ for 16 h of light and 8 h of darkness. After 7 days of culture, 100 mL of 0.2 mol / L NaCl solution was applied three times. The culture lasted for 14 days. The growth was observed and recorded, and various growth indicators were statistically analyzed.

[0062] 4. Results Analysis like Figure 5As shown, under pot cultivation conditions, and under both salt stress and no salt stress, plants inoculated with strain Ns399 showed significantly higher fresh weight, plant height, chlorophyll content, and leaf width than the control group. Both the overall plant performance and individual plant performance indicated that plants inoculated with strain Ns399 exhibited better growth than the uninoculated group.

[0063] The above description is merely a specific embodiment of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. All equivalent modifications or substitutions made based on the essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An endophytic fungus Ns399, characterized by, The endophytic fungus Ns399 is isolated from Pteridium aquilinum, and is classified and named as Nodulisporium Pteridium aquilinum sp. Ns399, and is preserved in China Center for Type Culture Collection with a preservation number of CCTCC NO: M20252459.

2. The endophytic fungus Ns399 of claim 1, wherein, The strain culture condition is that the endophytic fungus Ns399 is inoculated on PDA solid culture medium and cultured in darkness at 22-25℃ for 5-10 days.

3. A solid fungal inoculum of the endophytic fungus Ns399, characterized in that, The preparation method of the solid bacterial fertilizer comprises the following steps: inoculating the endophytic fungus Ns399 in claim 1 into a liquid fermentation culture medium, culturing to obtain a fermentation liquor, inoculating the fermentation liquor into sterile barley grains, and culturing in darkness until mycelium grows on the barley grains to obtain the Ns399 solid bacterial fertilizer; the composition of the liquid fermentation culture medium is that 5 g of potato powder, 10 g of peptone and 15 g of glucose are contained in 1000 mL.

4. The endophytic fungus Ns399 solid bacterial manure of claim 3, characterized in that, The fermentation liquor and the sterile barley grains are mixed at a ratio of 150 mL:200 g, and cultured in darkness at 25℃ until mycelium grows on the barley grains to obtain the Ns399 solid bacterial fertilizer.

5. The application of the endophytic fungus Ns399 in claim 1 in improving the salt stress tolerance of rice.

6. Use according to claim 5, wherein The application comprises the following steps: after rice seeds are germinated, the endophytic fungus Ns399 is co-cultured with the rice seeds to colonize the rice seedling roots, so that the growth of the rice seedlings is promoted and the salt stress tolerance of the rice seedlings is improved.

7. Use according to claim 6, wherein The application comprises the following steps: the endophytic fungus Ns399 is prepared into a solid bacterial fertilizer, mixed into a seedling raising substrate to obtain a mixed substrate, and rice seeds are sowed in the mixed substrate to raise seedlings, so that rice seedlings are obtained.

8. The use according to claim 6, wherein The co-culture condition is that the rice seeds are cultured at 22-25℃ with 16 h light and 8 h darkness.

9. The use of the endophytic fungus Ns399 according to claim 1 for promoting the growth of rice, characterized in that, The application comprises the following step: the endophytic fungus Ns399 is colonized in the rice root tissues.

10. Use according to claim 9, wherein The indexes of the rice growth comprise fresh weight, plant height, chlorophyll content and leaf width.

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