Arbuscular mycorrhizal fungus inoculant for improving growth vigor of pepper in seedling stage and yield of pepper and application of arbuscular mycorrhizal fungus inoculant

Abstract

The invention discloses an arbuscular mycorrhizal fungi inoculant for improving growth vigor and yield of pepper in a pepper seedling stage and application of the arbuscular mycorrhizal fungi inoculant, relates to the technical field of agricultural biology, and solves the problem of an AMF inoculant which is optimally combined according to pepper variety characteristics and can stably, efficiently and comprehensively improve the quality and final yield of pepper seedlings. According to the technical scheme, the method is characterized in that three kinds of fungicide, namely, rhizosporium intraradices, phomotheca mosseae and glomus parvicularis, are used for conducting independent inoculation on chilies, the spore concentration of the inoculant of the rhizosporium intraradices is 200 per gram, the spore concentration of the inoculant of the phomotheca mosseae is 370 per gram, and the spore concentration of the inoculant of the glomus parvicularis is 290 per gram; the method has the effects that the infection success rate and stability are improved: the fungicide provides various infection strategies and functional hypha networks, the probability of successfully establishing symbiotic relationships with root systems of different pepper varieties is increased, and the stability of the growth promoting effect is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural biotechnology, and particularly relates to a cluster root mycorrhizal fungus inoculant for improving growth potential of pepper seedlings and pepper yield and application thereof. BACKGROUND

[0002] Pepper is one of the largest vegetable crops in China, with an annual planting area of more than 213.33 million mu, and has a very high economic value. However, there are problems such as long seedling period, sensitivity to nutrient demand, and prominent continuous cropping obstacles in pepper production. The large-scale use of traditional chemical fertilizers and pesticides not only has high cost, but also easily leads to soil degradation, environmental pollution and decline of agricultural product quality.

[0003] Arbuscular mycorrhizal fungi (AMF) is a kind of beneficial soil microorganism that can form symbiotic bodies with most terrestrial plant roots. They greatly expand the absorption area of plant roots by extending root exosporal hyphae, helping host plants more effectively absorb phosphorus, nitrogen, zinc and other mineral nutrients and water (see documents 8, 10). In addition, AMF can also induce plants to produce systemic stress response, such as increasing the activity of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), thereby enhancing the tolerance of plants to abiotic stresses such as drought, salinity, heavy metals, etc. (see documents 12-18, 29).

[0004] At present, although there are reports of single AMF inoculants applied to peppers (such as documents 4, 20), there are obvious limitations: strong variety specificity: the same AMF strain has significant differences in growth promotion effect on different pepper varieties. For example, the document data shows that Glomus intraradices (GI) has excellent growth promotion effect on 'Sujiu 1614' and 'Xianhong No. 1', but the effect on 'Guota 181' is not as good as Glomus caledonium (GC).

[0005] Infection rate and effectiveness do not match: high infection rate does not always mean the best growth promotion effect. For example, as indicated in the document, on 'Sujiu 1614', the infection rate of GM is the highest (67.51%), but the promotion effect on the aboveground part is not as good as GI and GC with lower infection rates. This shows that there is a bottleneck in the function of a single strain.

[0006] Single function: different AMF strains have different advantages in promoting nutrient absorption, enhancing photosynthesis, and activating antioxidant systems, and a single strain cannot achieve comprehensive and stable growth promotion and stress resistance effect.

[0007] Therefore, there is an urgent need in the art for an AMF inoculant that can overcome the above-mentioned defects, optimize the combination according to the characteristics of pepper varieties, and stably and efficiently improve the quality of pepper seedlings and the final yield of peppers. SUMMARY

[0008] The present application aims to provide a cluster root mycorrhizal fungus inoculant for improving the growth potential of pepper seedlings and the yield of peppers and an application thereof, so as to solve the problems in the background art.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0010] A cluster root mycorrhizal fungus inoculant for improving the growth potential of pepper seedlings and the yield of peppers, the active ingredients of which are three strains of Endogone intraradices, Glomus mosseae and Glomus aggregatum, respectively, which are independently used for inoculation.

[0011] Preferably, the spore concentration of the three strains is 200, 370 and 290 per gram of inoculant.

[0012] Preferably, the dosage form of the inoculant is a solid inoculant, and the carrier thereof comprises one or more of grass carbon, vermiculite or plant residues.

[0013] Preferably, the application of the cluster root mycorrhizal fungus inoculant for improving the growth potential of pepper seedlings and the yield of peppers is to apply the cluster root mycorrhizal fungus inoculant to the seedling substrate in the seedling stage of peppers.

[0014] Preferably, according to the above-mentioned application, the application amount of the inoculant is 1 gram per hole.

[0015] Preferably, according to the above-mentioned application, the application amount of the inoculant is 1 gram per hole, and the inoculant is mixed with the substrate and applied at the time of sowing.

[0016] Preferably, according to the above-mentioned application, the improvement of the growth potential of pepper seedlings is at least one of the following indexes:

[0017] a) plant height, with an improvement of 10%;

[0018] b) stem diameter, with an improvement of 10%;

[0019] c) fresh weight of aboveground part, with an improvement of 15%;

[0020] d) fresh weight of underground part, with an improvement of 40%;

[0021] e) chlorophyll SPAD value, with an improvement of 45%.

[0022] Preferably, according to the above-mentioned application, the antioxidant enzyme activity of the pepper seedlings is significantly enhanced (p<0.05), and at least one of the following indexes is improved:

[0023] a) peroxidase (POD) activity is improved by 30%;

[0024] b) superoxide dismutase (SOD) activity is increased by 85%;

[0025] c) catalase (CAT) activity is increased by 15%

[0026] The pepper variety is selected from Suojiao 1614, Xianhong No. 1 or Guota 181.

[0027] When the pepper variety is Suojiao 1614 or Xianhong No. 1, the method can achieve a growth promotion and yield increase effect comparable to or better than inoculation with a single Endogone radicatum;

[0028] When the pepper variety is Guota 181, the method can achieve a growth promotion and yield increase effect comparable to or better than inoculation with a single Glomus intraradices.

[0029] Compared with the prior art, the beneficial effects of the present application are:

[0030] (1) Synergistic effect, comprehensive growth promotion: GI, GM and GC have complementary functions. GI is outstanding in promoting the plant height, aboveground dry weight and fruit fresh weight of 'Suojiao 1614' and 'Xianhong No. 1' (increasing by 16.69%, 15.37% and 86.31% respectively); GM is obviously superior in increasing the underground biomass of 'Suojiao 1614' (fresh weight increased by 46.75%) and the chlorophyll SPAD value of 'Xianhong No. 1' (increased by 50.6%); GC contributes the most to the stem diameter, yield (increased by 29.62%) of 'Guota 181' and the chlorophyll SPAD value of 'Suojiao 1614' (increased by 57.95%). After inoculation of the three separately, they can achieve synergistic promotion of the growth, photosynthesis, stress resistance and yield component factors of different pepper varieties.

[0031] (2) Enhanced stress resistance, strong seedling cultivation: the inoculant can significantly activate the antioxidant system of pepper seedlings. The data show that the POD, SOD and CAT activities of pepper leaves are significantly improved after inoculation, for example, the SOD activity of 'Suojiao 1614' is increased by 106.37%. This indicates that the present application not only promotes growth, but also improves the intrinsic stress resistance of the plant, which is helpful for cultivating strong and resistant seedlings.

[0032] (3) Increased infection success rate and stability: the inoculant provides multiple infection strategies and functional mycelial networks, increases the probability of successfully establishing a symbiotic relationship with the root system of different pepper varieties, and ensures the stability of the growth promotion effect.

[0033] (4) Yield increase and quality improvement, significant benefits: the present application can significantly improve the fruit morphology (fruit transverse diameter, longitudinal diameter) and single fruit fresh weight of pepper, and ultimately achieve a significant increase in single plant yield, with a maximum yield increase of 42.55%, which has clear economic benefits.

[0034] (5) Environment-friendly and strong sustainability: the present application belongs to biological agents, which reduces the dependence of agricultural production on chemical fertilizers, and conforms to the development direction of green and sustainable agriculture. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 1 is a diagram of the infection of pepper seedling roots by arbuscular mycorrhizal fungi.

[0036] Figures 2-1 to 2-8 are diagrams of the effects of inoculation with different AMFs on the growth of Supepo 1614.

[0037] Figures 3-1 to 3-8 are diagrams of the effects of inoculation with different AMFs on the growth of Xianhong No. 1.

[0038] Figures 4-1 to 4-8 are diagrams of the effects of inoculation with different AMFs on the growth of Guota 181.

[0039] Figure 5 Figure 5 is a diagram of the effects of inoculation with different AMFs on the chlorophyll SPAD of peppers.

[0040] Figure 6 Figure 6 is a diagram of the effects of inoculation with different AMFs on the activities of POD, SOD and CAT of peppers.

[0041] Figure 7 Figure 7 is a diagram of the effects of inoculation with arbuscular mycorrhizal fungi on the yield of a single pepper plant.

[0042] Figure 8 Figure 8 is a principal component analysis and clustering heat map of various indicators of pepper seedlings inoculated with arbuscular mycorrhizal fungi. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0044] 1. The present application mainly includes:

[0045] 2. Test materials

[0046] 2.1 Test materials

[0047] Tested pepper varieties: Supepper 1614 and Xianhong No.1, fresh pepper type; Guota 181, dry pepper type. Fresh and full pepper seeds were selected, disinfected with 75% alcohol, and washed with sterile water. The cultivation substrate was sterilized in a high-pressure sterilization pot at 121℃, 0.1 MPa for 2 h, and then cooled for standby, with a pH value of 6.9, total nitrogen content of 1%, total phosphorus content of 2%, total potassium content of 2%, and organic matter content of 39%. The strain selection was mixed spores of five strains including Glomus mosseae and Gigaspora rosea (referred to as mixed spores), Glomus intraradices (referred to as GI), Glomus mosseae (referred to as GM), Gigaspora rosea (referred to as GR), and Glomus claroideum (referred to as GC), with a spore concentration of 200-570 per gram.

[0048] 2.2 Test method

[0049] The test adopted a single-factor random test design. Six treatments were set, with no inoculation as the control, and the other five arbuscular mycorrhizal fungi were inoculated at the time of sowing. Sowing was carried out by using 72-hole hole plate seedling raising, and the hole plate was disinfected with 75% alcohol before use. At the time of inoculation, 1 gram of inoculant was added to each hole after the substrate was fully laid. The test was carried out in Chaimi River Agricultural Technology Co., Ltd. in Huai'an from September 2024 to February 2025.

[0050] 2.3 Index determination and method

[0051] The root system was washed and cut into 1 cm root segments, and then subjected to steps such as transparency, bleaching, acidification, staining (trypan blue staining method 19), and decolorization. Each sample was made into 3 pieces of glass sheet, with 10 root segments on each piece, and a total of 30 root segments. Finally, the mycorrhizal infection rate was observed under an optical microscope and calculated by the cross method.

[0052] Total infection rate = [(total cross point number-no infection cross point number) ÷ total cross point number] x 100%

[0053] At 40 d of growth, seedlings with consistent growth vigor were randomly selected from each treatment, and the plant height and stem diameter were measured using a vernier caliper; the dry and fresh weights of the aboveground and underground parts of the plant were measured using a thousandth scale. When measuring the dry weight, the aboveground and underground parts were placed in envelopes, and then placed in an oven for drying treatment at 105℃ for 5 min to remove residual moisture and fix the plate samples, and then reduced to 80℃ for drying to constant weight.

[0054] At 60 days of growth, seedlings with uniform growth were randomly selected from each treatment, and chlorophyll content was measured using a handheld chlorophyll meter. Superoxide dismutase (SOD) activity was measured using the nitroblue tetrazolium method, peroxidase (POD) activity was measured using the guaiacol method, and catalase (CAT) activity was measured using the potassium permanganate titration method.

[0055] During the peak fruiting period of chili peppers, chili pepper fruits were collected from each treatment, washed and dried, and the longitudinal and transverse diameters of the fruits were measured using vernier calipers. The fresh weight of the fruits was determined using a 0.1 g electronic balance. After blanching at 95°C for 15 min, the fruits were dried at 60°C to constant weight, and the dry weight of the fruits was determined.

[0056] 2.4. Data Analysis and Processing

[0057] The data was processed using Microsoft Office 2021 and IBM SPSS Statistics 27, and the relevant charts were created using Origin 2024.

[0058] 3. Results and Analysis

[0059] 3.1 Effects of AMF on pepper root infection rate

[0060] Depend on Figure 1 It can be seen that after successful infection by arbuscular mycorrhizal fungi, structures such as vesicles, spores, and arbuscular structures can be clearly observed. The mycorrhizal infection rates of the various treatments of Sujiao 1614 were as follows: CK 0, original spores 59.74%, GI 57.65%, GM 67.51%, GR 47.19%, GC 66.19%; the mycorrhizal infection rates of the various treatments of Xianhong No. 1 were as follows: CK 0, original spores 43.31%, GI 48.29%, GM 30.78%, GR 35.52%, GC 52.67%; the mycorrhizal infection rates of the various treatments of Guota 181 were as follows: CK 0, original spores 27.82%, GI 22.38%, GM 32.67%, GR 54.15%, GC 59.71%. Compared with the control, there were differences in infection rates among the five inoculation treatments (p<0.05). The infection rates of different arbuscular mycorrhizal fungi (AMFs) on the root systems of different pepper varieties also showed significant differences. The original strain of AMF achieved an infection rate of 59.74% on Sujiao 1614, while it only achieved 43.31% and 27.82% on Xianhong No. 1 and Guota 181, respectively. The infection rate of GI on Guota 181 was only 22.38%, while it reached 57.65% and 48.29% on Sujiao 1614 and Xianhong No. 1, respectively. The results indicate that all five arbuscular mycorrhizal fungi can infect the root systems of the three pepper varieties. Among them, GM had the highest infection rate on Sujiao 1614, while GC had the highest infection rate on Xianhong No. 1 and Guota 181.

[0061] 3.2 Effects of different AMFs on the vegetative growth of peppers

[0062] Figures 2 to 4 show that AMF inoculation affected the growth of the three pepper species. The plant height, stem diameter, and dry and fresh weight of both the above-ground and underground parts of the peppers treated with AMF differed from the control. Specifically, from... Figure 5 , Figure 6 The results showed that the GI treatment resulted in the best plant height and aboveground dry weight for Sujiao 1614, significantly increasing by 16.69% and 15.37% respectively compared to the control. The GC treatment resulted in the best stem diameter and aboveground fresh weight, increasing by 12.85% and 18.76% respectively. The GM treatment resulted in the best underground fresh weight and underground dry weight, increasing by 46.75% and 19.64% respectively. Compared to the control, the GI treatment significantly improved the plant height and stem diameter of Xianhong No. 1, while there were no significant differences among other treatments. Except for the best aboveground fresh weight under the GR treatment, the GC treatment significantly improved the plant height and stem diameter of Guota 181. These results indicate that all AMFs promoted the vegetative growth of peppers to varying degrees. Among them, GI, GM, and GC showed the best promoting effect on Sujiao 1614; GI showed the best promoting effect on Xianhong No. 1; and GC showed the best promoting effect on Guota 181.

[0063] 3.3 Effects of AMF on chlorophyll SPAD in pepper leaves

[0064] Depend on Figure 7 It was found that the changes in chlorophyll SPAD under different AMF treatments were not entirely the same. Compared with the control, the chlorophyll SPAD of peppers infected with different AMFs was significantly greater than that of the control. For Sujiao 1614, the order was GC>GM>original strain>GR>GI; for Xianhong No. 1, it was GM>GR>GC>original strain>GI; and for Guota 181, it was GI>GM>GC>GR>original strain. Among them, Sujiao 1614, which was inoculated with GC, had the highest chlorophyll SPAD, increasing by 57.95%; Xianhong No. 1, which was inoculated with GM, had the highest chlorophyll SPAD, increasing by 50.6%; and Guota 181, which was inoculated with GI, had the highest chlorophyll SPAD, increasing by 53.76%. The results indicate that GI, GM, and GC have the most significant effects on chlorophyll SPAD.

[0065] 3.4 Effects of AMF on the activities of POD, SOD, and CAT in pepper leaves

[0066] Depend on Figure 8It can be seen that the activities of antioxidant enzymes inoculated with different AMF are significantly different. Specifically, the activities of POD and SOD of Suojiao 1614 treated with five kinds of AMF are significantly higher than the control, the activities of POD are increased by 35.93%, 51.03%, 18.35%, 11.79%, 5.53%, respectively, and the activities of SOD are increased by 106.37%, 90.92%, 20.37%, 86.8%, 87.34%, respectively; the activity of CAT treated with original strain is higher than the control, but there is no significant difference with the control, and the activities of CAT treated with other treatments are significantly higher than the control, among which the activity of CAT treated with GI is the highest, which is increased by 19.05% compared with the control. The activities of POD of Xianhong No.1 treated with original strain, GI, GM and GR are significantly higher than the control, which are increased by 36.42%, 79.1%, 40.6% and 38.81%, respectively; the activities of SOD treated with other treatments except the original strain are significantly higher than the control, among which the activity of SOD treated with GI is the highest, which is increased by 103.78% compared with the control; the activities of CAT treated with other treatments except the original strain and GM are not significantly different from the control, among which the activity of CAT treated with the original strain is the highest. The activities of POD of Guota 181 treated with original strain, GM and GR are significantly lower than the control, which are decreased by 43.42%, 11.43% and 28.48%, respectively; the activities of SOD treated with other treatments except GM are significantly higher than the control, which are increased by 67.16%, 72.47%, 17.84%, 89.47% and 77.09%, respectively; the activities of CAT treated with five kinds of AMF are significantly higher than the control, among which the activity of CAT treated with the original strain is the highest. The above results show that GI and original strain have better effects on the activities of antioxidant enzymes of Suojiao 1614 and Xianhong No.1, and the obvious effects of GI, GR and original strain on Guota 181 are better.

[0067] Table 1 Effects of inoculation with different AMF on the morphology of pepper fruits

[0068]

[0069]

[0070] 3.5 Effects of AMF on the morphology of pepper fruits

[0071] From Table 1, it can be seen that inoculation of AMF can significantly increase the fruit fresh weight of Suojiao 1614, Xianhong No.1 and Guota 181, which is increased by 14.54%-86.31%, 26.2%-53.81%, 31.13%-46.75% compared with the control, respectively. The fruit fresh weight of Suojiao 1614 and Xianhong No.1 is increased by 86.31% and 53.81% by inoculation of GI, respectively, and the fruit fresh weight of Guota 181 is increased by 46.75% by inoculation of GC. From Table 1, it can be seen that the fruit transverse and longitudinal diameters of Suojiao 1614 are significantly increased by 6.91%-32.32% and 3.8%-29.59% compared with the control, respectively, and the effect of GI on the fruit morphology of Suojiao 1614 is the largest. In addition to significantly increasing the fruit fresh weight of Xianhong No.1, inoculation of AMF also significantly increases the fruit longitudinal diameter, but has no significant difference on the fruit transverse diameter. The fruit longitudinal diameter of Xianhong No.1 is increased by 11.15%-42.9% compared with the control, and the increase of GI is the largest, which is 42.9%. Compared with the control, inoculation of AMF significantly increases the fruit transverse and longitudinal diameters of Guota 181, which is increased by 9.58%-21.8% and 11.5%-20.4%, respectively, and the increase of GI is the largest. The above results show that the effect of GI on the fruit fresh weight of the three kinds of peppers is the largest.

[0072] 3.6Effect of AMF on the yield of pepper

[0073] In addition to the original strain treatment, the single plant yield of Suojiao 1614 treated with different AMF is significantly different, and the single plant yield of Suojiao 1614 treated with GI is the highest, which is increased by 38.22% compared with the control. The single plant yield of Xianhong No.1 treated with five kinds of AMF is significantly higher than that of the control, and the growth rate is 11.58%-42.55%. The single plant yield of Guota 181 treated with GI has no significant difference with the control, and the single plant yield of Guota 181 treated with other treatments is significantly higher than that of the control, and the single plant yield of Guota 181 treated with GC is the highest, which is increased by 29.62% compared with the control. The above results show that the effect of GI on the single plant yield of Suojiao 1614 and Xianhong No.1 is the best, and the effect of GC on the single plant yield of Guota 181 is the best.

[0074] 3.7Principal component analysis and cluster of AMF on the growth and physiological indexes of different pepper seedlings

[0075] In this study, principal component analysis (PCA) was used to analyze all the indicators of Suojiao 1614, Xianhong No.1 and Guota 181 and their six treatments. The results showed that the first two principal components PC1 and PC2 explained 84.8% of the total variance, indicating that the reduced data could well represent the information of the original indicators. PC1 mainly included stem diameter, aboveground fresh weight, underground fresh weight, aboveground dry weight, fruit transverse diameter, fruit longitudinal diameter and yield per plant, while PC2 mainly included SPAD, POD, SOD, fruit transverse diameter and fruit fresh weight. Therefore, PC1 could be regarded as the main component of plant growth and yield, while PC2 reflected more the antioxidant defense ability and photosynthetic characteristics. The score plot showed that the control and AMF treatments of each variety could be well distinguished, indicating that AMF inoculation could effectively promote the growth of pepper and enhance its stress resistance.

[0076] In this cluster analysis, all indicators were systematically clustered using the group average method and Euclidean distance for similarity measurement. The results showed that all indicators could be divided into three clusters. Cluster a was SOD activity, cluster b was POD activity, CAT activity, SPAD, fruit transverse and longitudinal diameter, fruit fresh weight and yield per plant, and cluster c included plant height, stem diameter, dry and fresh weight of aboveground and underground parts. According to the color intensity, the values of AMF inoculated seedlings were higher than those of the control.

[0077] 4. Discussion

[0078] AMF affects plant growth by infecting host plants and producing mycorrhizal effects. There is mutual selectivity between arbuscular mycorrhizal fungi and plants. The same fungus has different responses to different plants, and the same plant has different responses to different fungi 20 The results of this experiment showed that AMF inoculation had good infection effect on the root system of pepper seedlings. The mycorrhizal infection rate of Suojiao 1614 root segments inoculated with GM fungus was as high as 67.51% after 45 days, and the mycorrhizal infection rate of Xianhong No.1 and Guota 181 root segments inoculated with GC fungus was as high as 52.67% and 59.71% respectively, which played a certain role in the growth of seedlings, indicating that a stable symbiotic system had been established between AMF and pepper roots. 21 When inoculating AMF on Chinese fir seedlings, it was found that the root infection rate under GM inoculation was significantly higher than that of other types of AMF. 22When peppers were inoculated with four different mycorrhizal fungi (AMFs), the infection rates were all found to be higher than 60%. While high infection rates were also observed in pepper roots in this study, lower infection rates were also observed. This indicates that under the same growth conditions, the infection rates of different AMFs on plant roots vary. This is likely due to the influence of many biotic and abiotic factors. Different AMFs interact differently with their host plants and possess different biological characteristics, including hyphal growth rates and infection strategies, thus leading to different infection characteristics on plant roots. 23,24 .

[0079] Arbuscular mycorrhizal fungi can promote the growth of host plants by activating soil nutrients, expanding the root system's absorption area, enhancing photosynthesis, and improving physiological conditions. 25 It is generally believed that the infection rate is positively correlated with the growth-promoting effect; that is, the higher the infection rate, the greater the degree of mycorrhizalization of the host plant, and the more significant the promoting effect on plant growth and development. 26,27 However, this study found that different peppers inoculated with different AMFs exhibited low mycorrhizal infection rates but better promotion of certain growth indicators, specifically in multiple aspects of growth and physiology. For example, inoculating Sujiao 1614 with GI and GC resulted in lower infection rates than GM treatment, but its effect on aboveground growth was more significant than GM. Similarly, inoculating Xianhong No. 1 with GC showed the highest infection rate compared to other inoculants, but its growth-promoting effect was weaker than GI. Likewise, GC showed the highest infection rate in Guota 181, but GR had a 4.04% higher effect on aboveground fresh weight than GC. Chlorophyll, as the most important pigment molecule in photosynthesis, participates in the absorption, transfer, and conversion of light energy during photosynthesis. Existing studies have confirmed... 28 Arbuscular mycorrhizal fungi (AMF) can increase the chlorophyll content of plants. In this study, inoculation with GC, GM, and GI showed the most significant effects on increasing the SPAD value of chlorophyll in pepper varieties such as Sujiao 1614, Xianhong No. 1, and Guota 181, but their infection rates were not the highest. Arbuscular mycorrhizal fungi can enhance the activity of antioxidant enzymes in host plants and promote the synthesis of antioxidants, thus reducing the harmful effects of reactive oxygen species in plants. 29 In this study, inoculation with the original strain, GI, and GR significantly enhanced the activities of POD, SOD, and CAT in peppers compared to other treatments. However, none of these three inoculants resulted in the highest mycorrhizal infection rate. These results are consistent with previous research findings. 30,31 This is inconsistent with previous research, which has shown that fungal strains with high infection rates have a more significant effect on plant biomass, such as plant height and stem diameter, and are more effective at increasing chlorophyll content compared to fungal agents with lower infection rates. This phenomenon may be because not all arbuscular mycorrhizal fungi (AMFs) effectively promote host plant growth; some even exhibit negative effects. This suggests that the effects of mycorrhizae on plants cannot be entirely represented by mycorrhizal infection rates, and different AMFs have different impacts on plant growth. This aligns with Thomsen's findings.32 et al. 33 The results of the research of Qian et al. are similar, indicating that the affinity between the strain and the host and the positive effect are not necessarily linearly positively correlated. It is speculated that the reason may be that different arbuscular mycorrhizal fungi have different structural characteristics, and their ability to absorb nutrients and water is also different. In addition, it may be affected by many factors such as mycorrhizal activity, the ratio of intramycorrhizal and extramycorrhizal hyphae, and the distribution of extramycorrhizal hyphae in the rhizosphere, resulting in that the effect of the infection rate on the host plant is sometimes consistent and sometimes inconsistent. 34 .

[0080] Inoculation of AMF can improve root architecture, promote root hair growth, and increase the absorption of water and nutrients by plants 35,36 . The formed mycorrhizal roots can increase the activity of antioxidant enzymes in host plants and promote the synthesis of antioxidants, reduce the damage of reactive oxygen species in plants, and significantly enhance the stress resistance of peppers 29 , increase yield and quality. The results of this study show that the SOD activity of Supeijia 1614 and Xianhong No. 1 increased most significantly after inoculation with AMF, with an average increase of 1.78 times and 1.77 times, respectively. The underground fresh weight of Guota 181 increased most significantly, with an average increase of 2.81 times, which was significantly higher than other indicators. This indicates that inoculation with AMF significantly enhances the antioxidant system activity of peppers, promotes root construction and the absorption of nutrients, and lays a foundation for the growth of the aboveground part and fruit development. The increase in chlorophyll content also means an increase in photosynthetic efficiency, which further supports nutrient accumulation and fruit development. 37 The results of this study show that inoculation with AMF increased the single weight of tomato fruit by 1.16 times, and the total yield was significantly improved. 20 The results of this study show that inoculation with AMF increased the single weight of tomato fruit by 1.16 times, and the total yield was significantly improved. 37 The results of this study show that inoculation with AMF increased the single weight of tomato fruit by 1.16 times, and the total yield was significantly improved. 20 The results of this study show that inoculation with AMF increased the single weight of tomato fruit by 1.16 times, and the total yield was significantly improved. 37 The results of this study show that inoculation with AMF increased the single weight of tomato fruit by 1.16 times, and the total yield was significantly improved. 20 The results of this study show that inoculation with AMF increased the single weight of tomato fruit by 1.16 times, and the total yield was significantly improved.

[0081] 5. Conclusion

[0082] The results showed that five kinds of arbuscular mycorrhizal fungi could form infection on three kinds of pepper, but the infection characteristics and growth-promoting effects were different. Principal component analysis showed that AMF mainly improved the growth, yield and stress resistance of pepper by promoting the growth of aboveground part, enhancing photosynthetic capacity and antioxidant enzyme activities such as POD and SOD. This study provided scientific reference for subsequent utilization of mycorrhizal technology to cultivate disease-free seedlings with good growth and improve production potential. Among them, Suojiao 1614 and Xianhong No. 1 inoculated with Glomus intraradices had better effect, and Guota 181 inoculated with Glomus claroideum had better effect.

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[0122] It is apparent to a person skilled in the art that the present application is not limited to the details of the above-described exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the present application being defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and range of equivalency of the claims' elements be embraced therein. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

[0123] Furthermore, it should be understood that although the present specification describes exemplary embodiments, not every embodiment contains only one independent technical solution, and the present specification is described in this way only for the sake of clarity, and a person skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that a person skilled in the art can understand.

Claims

1. An arbuscular mycorrhizal fungal inoculant for enhancing the growth vigor of chili seedlings and increasing chili yield, characterized in that, Its active ingredients are three species of fungi: Rhizocystis radiata, Rhizocystis mosesi, and Rhizocystis spp., which are used independently for inoculation.

2. The arbuscular mycorrhizal fungal inoculant for enhancing the growth vigor and yield of chili seedlings according to claim 1, characterized in that, The spore concentrations of Rhizocystis radicans, Rhizocystis mosesi, and Rhizocystis spp. were 200, 370, and 290 spores per gram of inoculum, respectively.

3. The arbuscular mycorrhizal fungal inoculant for enhancing the growth vigor and yield of chili seedlings according to claim 1, characterized in that, The inoculant is in the form of a solid inoculant, and its carrier includes one or a combination of several of the following: peat moss, vermiculite, or plant residues.

4. The application of the arbuscular mycorrhizal fungal inoculant according to any one of claims 1-5 in improving the growth vigor of chili seedlings and the yield of chili peppers, characterized in that, During the seedling stage of chili peppers, arbuscular mycorrhizal fungi inoculants are applied to the seedling substrate.

5. The application according to claim 1, characterized in that, The inoculum is applied at a rate of 1 gram per hole.

6. The application according to claim 1, characterized in that, The inoculum is applied at a rate of 1 gram per hole and is mixed with the substrate at the time of sowing.

7. The application according to claim 1, characterized in that, The improvement in the growth vigor of chili seedlings is specifically manifested in a significant increase in at least one of the following indicators (p<0.05): a) Plant height, with an increase of no less than 10%; b) Stem thickness, with an increase of no less than 10%; c) The fresh weight of the above-ground parts shall be increased by no less than 15%; d) The fresh weight of the underground part shall be increased by no less than 40%; e) Chlorophyll SPAD value, with an increase of no less than 45%.

8. The application according to claim 1, characterized in that, The antioxidant enzyme activity of the pepper seedlings was significantly enhanced (p<0.05), specifically demonstrated by at least one of the following indicators: a) Peroxidase (POD) activity increased by no less than 30%; b) The activity of superoxide dismutase (SOD) is increased by no less than 85%; c) The activity of catalase (CAT) is increased by no less than 15%.

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