CN108605706B

CN108605706B - Method for improving cadmium resistance of tomatoes

Info

Publication number: CN108605706B
Application number: CN201810231150.1A
Authority: CN
Inventors: 王诗忠; 李元媛; 曾加会; 黄礼格; 阮迪申; 仇荣亮; 晁元卿; 汤叶涛
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2018-03-20
Filing date: 2018-03-20
Publication date: 2021-04-27
Anticipated expiration: 2038-03-20
Also published as: CN108605706A

Abstract

The invention provides a method for improving cadmium resistance of tomatoes, which comprises the following steps: 1) transplanting the tomato seedlings into cadmium-polluted soil and inoculating AMF microbial inoculum at the same time; 2) after the tomato seedlings stably grow, inoculating plant rhizosphere growth-promoting bacteria agent into the plant root systems; 3) tomatoes are cultured until they mature and produce fruit. The invention realizes the promotion of the growth of the tomatoes under the cadmium stress by the co-inoculation of the plant rhizosphere growth-promoting bacteria and the arbuscular mycorrhizal fungi, can reduce the content of heavy metals in the plants, does not influence the property of the soil, provides a direction for the research of the combined action of the plant rhizosphere growth-promoting bacteria and the AMF on the growth of the plants and the metal tolerance, and provides a line for the research of the action mechanisms of the plant rhizosphere growth-promoting bacteria and the AMF.

Description

Method for improving cadmium resistance of tomatoes

Technical Field

The invention belongs to the technical field of heavy metal pollution remediation, and particularly relates to a method for improving cadmium resistance of tomatoes, in particular to a method for promoting growth of tomato plants under cadmium stress by using plant rhizosphere growth-promoting bacteria and sacculus mossambicus.

Background

The heavy metal pollution of farmland is getting more and more serious, can inhibit the growth of crops to reduce the crop yield, and also seriously threatens the health of human beings. In order to improve the current situation of heavy metal pollution of farmlands, the plant restoration technology is widely applied, and plant barrier also becomes one of important restoration technologies for improving the safety of agricultural products. The improvement of the growth condition of crops by adding chemical modifiers or microbial assistance means has certain effect, but the addition of the chemical modifiers has influence on the fertility and the structure of soil or has the risk of secondary pollution, so the rise of microbial fertilizers is concerned.

Plant growth-promoting rhizobacteria (PGPR) can promote plant growth and improve plant heavy metal tolerance by secreting indole-3-acetic acid (IAA), siderophores, nitrogen and phosphorus fixation and the like. A great deal of research results show that the plant growth-promoting rhizobacteria can assist plants to repair polluted soil, so that the plant repair efficiency is improved. Dell 'Amico et al inoculated Brassica napus grown under Cd stress with a Cd-resistant strain producing IAA, siderophore and 1-aminocyclopropane-1-carboxylate (ACC) deaminase, promoted plant growth and increased total Cd accumulation by plants (Dell' Amico, E., L.Cavalca, and V.Androeoni, Improvement of Brassica napus growing under calcium stress by cadmium-resistant strain 2008.40(1): p.74-84.). However, a great number of microorganisms exist in the plant rhizosphere, the interaction process is complex, the assisting effect of a single bacterium is not obvious, and therefore the effect of the combined action of a plurality of microorganisms on plant repair cannot be ignored.

Arbuscular Mycorrhizal Fungi (AMF) widely existing in nature can infect plant roots to change root morphology and mineral nutrition conditions, heavy metals can be adsorbed by mycelia, secondary metabolites such as sacchricin, organic acids and plant auxin can be generated to change the bioavailability of the heavy metals, so that the plant growth is promoted, and the heavy metal resistance of the plant is enhanced. Researches on Liu ganoderma and the like find that the plant biomass can be obviously increased by inoculating Tumbaria mossambicolor to corn at a high Cd level, the concentration of Cd in a root system is increased, and the transportation of Cd to the upper part of the corn field is reduced. In addition, there is a certain synergistic effect between AMF and PGPR, and a great deal of research has been carried out on the synergistic effect of PGPR and AMF on plant growth (Liu ganoderma, et al, the effect of arbuscular mycorrhizal fungi (Glomumamoseae) on cadmium uptake in corn. soil report, 2011.42(3): p.568-572.). Julie et al showed that co-inoculation of P.putida (Pseudomonas putida) and indigenous AMF significantly increased the root dry weight, nodulation number and nutrient status of the clover, while P.putida also promoted colonization of AMF on plant roots (JULIE R.MEYER and R.G.LINERMAN, Response of sub-tertiary closure to dual infection with a novel fungal fasciculus fasciculatus variant and a plant growth-promoting bacterium, P.185-190, 1986.18 (2)). The study by Medina et al also found that co-inoculation of Glomus deserticola (Glomus degerticola) and Bacillus pumilus (Bacillus pumilus) maximized alfalfa biomass and root length relative to single inoculation (Medina, A., et al., Interactions of arbuscula-mycorrhizal fungi and Bacillus strains and their effects on plant growth, microbial biomass activity (which and leucovorin) and fungal biomass (ergosterol and chitin) Applied Soeclogy, 2003.22 (1): p.15-28.). The simultaneous inoculation of Pseudomonas fluorescens (Pseudomonas fluorescens) and AMF into Maize plants synergistically promotes increased crop yield (Berta, G., et al., Maize degradation and grain quality area differentiated inoculated by mycorrichiazal fungi and a growth-promoting microorganism in the field. mycorrichza, 2014.24(3): p.161-70.).

The synergistic growth promoting effect of PGPR and AMF on plants has been widely focused, but studies on the synergistic promotion of plant growth and heavy metal tolerance by both under heavy metal stress are still rare.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for improving the cadmium resistance of tomatoes, which realizes the promotion of the growth of the tomatoes under the cadmium stress by the joint inoculation of plant rhizosphere growth-promoting bacteria and arbuscular mycorrhizal fungi, can reduce the content of heavy metals in the plants, does not influence the property of soil, provides a direction for the research of the combined action of the plant rhizosphere growth-promoting bacteria (PGPR) and AMF on the growth and metal resistance of the plants, and provides a line for researching the action mechanisms of the plant rhizosphere growth-promoting bacteria (PGPR) and the AMF.

In order to solve the above problems, in one aspect, the present invention provides a method for improving cadmium resistance of tomatoes, comprising the following steps:

1) transplanting the tomato seedlings into cadmium-polluted soil and inoculating AMF microbial inoculum at the same time;

2) after the tomato seedlings stably grow, inoculating plant rhizosphere growth-promoting bacteria agent into the plant root systems;

3) tomatoes are cultured until they mature and produce fruit.

Furthermore, the inoculation amount of the AMF microbial inoculum is 10-50 g/kg, and the AMF microbial inoculum is uniformly dispersed at a position 1-10 cm away from the surface layer of the soil.

Furthermore, the inoculation amount of the AMF microbial inoculum is 15-25 g/kg, and the AMF microbial inoculum is uniformly dispersed at a position 1-5 cm away from the surface layer of the soil.

Further, the inoculation amount of the AMF microbial inoculum is 20g/kg, and the AMF microbial inoculum is uniformly dispersed at a position 1-3 cm away from the surface layer of the soil.

Further, the AMF microbial inoculum is a common Gliocladium moxidense microbial inoculum. The sacculus mosaicus mildew agent may include a mixture of sacculus mosaicus host plant root segments, hyphae, mycorrhizal fungal spores, and/or a cultivation substrate. The host plant of the sacculus mochaeformis is corn, milk vetch, sorghum, clover or sudan grass and the like. The Glomus mosseae is Glomus mossea.

Further, the concentration of cadmium in the cadmium-polluted soil is 0-100 mg/kg.

Further, the concentration of cadmium in the cadmium-polluted soil is 0mg/kg, 50mg/kg and 100 mg/kg.

Further, the stable growth of the tomato seedlings means that the tomato seedlings grow into four true leaves.

Further, the plant growth-promoting rhizobacteria agent includes Enterobacter sp (hereinafter abbreviated as EG16) or Enterobacter ludwigii strain DJ3 (hereinafter abbreviated as DJ 3).

Further, the inoculation amount of the plant rhizosphere growth-promoting bacterium agent is 1 multiplied by 10⁶～1×10⁹CFU/kg, concentration of plant rhizosphere growth promoting bacteria agent is 1 multiplied by 10⁶～1×10⁹CFU/mL. Preferably, the inoculation amount of the plant rhizosphere growth-promoting bacterium agent is 5 multiplied by 10⁸CFU/kg, the concentration of the plant rhizosphere growth-promoting bacteria agent is 5 multiplied by 10⁸CFU/mL。

Furthermore, after the plant grows into four main leaves and stably grows, 1-5 mL of the plant rhizosphere growth promoting bacterial agent is inoculated to the root system of the plant. The plant rhizosphere growth-promoting bacterium agent is screened from heavy metal contaminated soil, and the specific process is as follows: soil samples collected from rhizosphere of various common crops in acidic mine wastewater polluted farmlands in Shanghai village in Guangdong province are coated and inoculated on LB solid culture medium (bacteriological peptone 10.0g, yeast extract 5.0g, NaCl 10.0g, deionized water 1L, agar 15g and pH 7.0) added with 30mg/L Cd (II) by a dilution coating method, bacteria with different forms and full growth are selected on a plate and are singly streaked on the solid culture medium containing Cd (II) (30mg/L), and enrichment and purification are continuously carried out for 2-3 times, so as to obtain pure culture of Cd resistant bacteria (Enterobacter sp (hereinafter abbreviated as EG16) or Enterobacter ludwigi strain DJ3 (hereinafter abbreviated as DJ 3). And coating the separated and purified test strains on an LB solid medium plate, culturing at the constant temperature of 30 ℃ for 48h, and selecting single well separated bacterial colonies to be sent to a biological company for 16S rRNA strain sequencing identification.

In another aspect, the invention provides a soil conditioner suitable for planting tomatoes in soil polluted by cadmium, comprising saccharum morganii and plant growth-promoting rhizobacteria, wherein the plant growth-promoting rhizobacteria comprise Enterobacter sp (hereinafter abbreviated as EG16) or Enterobacter ludwigii strain DJ3 (hereinafter abbreviated as DJ 3).

In another aspect, the present invention provides the use of saccaromyces mosseae, a plant growth-promoting rhizobacteria, or a combination thereof, in a method of reducing cadmium accumulation in tomatoes and increasing tomato yield; the plant growth-promoting rhizobacteria comprise Enterobacter sp (hereinafter abbreviated as EG16) or Enterobacter ludwigii strain DJ3 (hereinafter abbreviated as DJ 3).

Compared with the prior art, the invention has the following beneficial effects: the invention provides a method for improving cadmium resistance of tomatoes, which is characterized in that different plant rhizosphere growth-promoting bacteria and Musicella morganii are combined and inoculated to root systems of tomato plants, and the change of the cadmium resistance of the tomato plants under the stress of heavy metal cadmium is researched, so that the effect of obviously improving the Cd resistance of the tomato plants by inoculating the plant rhizosphere growth-promoting bacteria and the Musicella morganii (Gm) fungus under the stress of heavy metal Cd is obtained, and the improvement of the Cd resistance of the tomato plants by the co-inoculation of the strain EG16 and the Gm is most obvious.

The method selects two strains of bacteria PGPR (Enterobacter sp (hereinafter abbreviated as EG 16)) and Enterobacter ludwigii strain DJ3 (hereinafter abbreviated as DJ3)) with different growth promoting characteristics, strong Cd tolerance and good growth promoting potential and jointly inoculates Glomus mosseae (Glomus mossea (hereinafter abbreviated as Gm)) on a plant root system, analyzes the plant height, root length and biomass change after inoculation, the transfer capacity change of Cd (II) and the antioxidant enzyme activity change of the plant, researches the promotion effect of the strain inoculation on the tomato plant growth under the stress of heavy metal Cd, provides a direction for the research on the plant growth and metal tolerance under the combined action of plant rhizosphere growth promoting bacteria and AMF, and provides a line for researching the two action mechanisms.

The invention utilizes bacteria PGPR (Enterobacter sp (EG16 for short) and Enterobacter ludwigii strain DJ3 (DJ 3 for short) and arbuscular mycorrhizal fungi Glomus mosseae (Gm for short) to be jointly inoculated in the root system of tomato plants, thereby not only improving the fresh weight of the overground part and the root of the tomato and improving the yield of the tomato, but also inhibiting the migration of heavy metal from soil to plant bodies, reducing the potential risk of high-concentration Cd to edible parts of the plants, providing a way for the safe production of the tomato in the soil polluted by the heavy metal Cd, and having important significance for the production and application of the tomato.

The bacteria PGPR (Enterobacter sp. and Enterobacter ludwigii strain DJ3) and the arbuscular mycorrhizal fungi Glomus mosseae (Glomus mosseae) which are adopted by the invention are widely existed in the soil environment, and the Enterobacter sp. and the Enterobacter ludwigii strain DJ3 are also from the soil which can well pollute the rhizosphere of the farmland plants by heavy metals, can form good symbiosis with the plants, have strong cadmium resistance and good growth promotion potential, can promote the nutrient absorption of the plants, are green and environment-friendly additives, and can not cause secondary pollution.

Drawings

FIGS. 1 a-1 b show plant biomass under different strain treatments (data in the figure are mean values + -standard deviation of 3 parallels, significance analysis is performed between the same Cd concentrations, different lower case letters indicate that significance difference is achieved between treatment groups, p is less than 0.05; FIG. 2 is the same); length of the root length in the figure; height of the plant height; weight of root weight; weight of shot weight on the ground.

FIG. 2 Cd content in plants treated with different strains; the concentration of Cd in the root of the root in the diagram; the concentration of Cd in the overground part of the shot.

FIGS. 3a to 3c show the antioxidase activity (data in the figure are 3 parallel means. + -. standard deviation, different lower case letters indicate significant difference among treatment groups with the same Cd concentration, different upper case letters indicate significant difference among CK with different Cd concentrations, and p is less than 0.05); in the figure, POD activity; different strains of Differencen strains; (ii) CAT activity; SOD activity.

Detailed Description

The present invention will be further illustrated by the following examples, but is not limited thereto.

Example 1

The preparation process of the tested bacterial agent comprises the following steps: soil samples are collected from the rhizosphere of various common crops in acid mine wastewater polluted farmlands in the Shanghai village of Guangdong province. And (2) coating and inoculating the soil suspension to an LB solid culture medium (10.0 g of bacteriological peptone, 5.0g of yeast extract, 10.0g of NaCl, 1L of deionized water, 15g of agar and pH 7.0) added with 30mg/L Cd (II) by using a dilution coating method, selecting single bacterial colonies with different forms and full growth on a flat plate, streaking the single bacterial colonies on the solid culture medium containing Cd (II) (30mg/L), and continuously enriching and purifying for 2-3 times to obtain pure culture of Cd (Cd) resistant bacteria. And coating the separated and purified test strains on an LB solid medium plate, culturing at the constant temperature of 30 ℃ for 48h, and selecting single well separated bacterial colonies to be sent to a biological company for 16S rRNA strain sequencing identification. Selecting two strains of bacteria PGPR (Enterobacter sp (hereinafter abbreviated as EG16) and Enterobacter ludwigii strain DJ3 (hereinafter abbreviated as DJ3) with different growth promoting characteristics, strong Cd tolerance and good growth promoting potential, inoculating the activated bacterial suspension into a liquid culture medium at an inoculation amount of 2%, carrying out shaking culture at 30 ℃ and 180r/min for 24h to the initial stage of a stabilization period, transferring to a 50mL centrifuge tube 8000rpm, centrifuging at 4 ℃ for 10min, carrying out centrifugal washing with sterile water for three times for resuspension, adjusting OD (OD) of bacterial liquids of the strains EG16 and DJ3, and regulating the OD of the bacterial liquids of the strains EG16 and DJ3₆₀₀Are respectively provided with1.3 + -0.02, 0.5 + -0.02, and the number of bacteria cells is 5 × 10⁸CFU/mL。

The test fungi were selected from the universal and well-studied arbuscular mycorrhizal fungus, sacculus mosseae (Glomus mossea, abbreviated as Gm in the figure of the present invention), and purchased from mycorrhizal research institute of Qingdao agricultural university.

Collecting pollution-free farmland fertile soil (Cd pollution is approximately 0mg/kg, actual measurement data is 0.32 mg/kg) from southern China agricultural university, air-drying, grinding, and sieving with a 10-mesh sieve for later use. Mixing soil and quartz sand (2mm) at a volume ratio of 5:2, sterilizing with high pressure steam (121 deg.C, 2 hr), and placing 1.5L plastic pots with 1kg each pot. Preparing polluted soil samples with Cd pollution concentrations of 50mg/kg and 100mg/kg respectively by adopting a manual pollution adding method, and balancing for two weeks in a greenhouse for later use.

The experimental process comprises the following steps:

three Cd concentrations (0mg/kg, 50mg/kg, 100mg/kg, determined according to the previous preliminary experiment results) were set for the experiment, AMF (Glomus mossea, Gm), PGPR (EG16, DJ3) were inoculated separately and together, four in parallel for each treatment, for a total of 72 pots. The specific experimental arrangement is as follows

Cd concentration/inoculation Condition	0mg/kg	50mg/kg	100mg/kg
				CK
	1	7	13
				G.m	2	8	14
EG16	3	9	15
				G.m+EG16	4	10	16
DJ3	5	11	17
				G.m+DJ3	6	12	18

Selecting tomato seedlings with consistent growth vigor, transplanting the tomato seedlings into pots filled with 1kg of balanced soil samples, and transplanting two tomato seedlings in each pot; and (3) inoculating the AMF microbial inoculum at the same time of transplanting the plants, uniformly dispersing 20g of the AMF microbial inoculum in a position 1-3 cm away from the surface layer of the soil in each pot, and adding the sterilized AMF microbial inoculum with the same weight and 2mL of AMF microbial inoculum filtrate with the filtered Glomus mossea to maintain the same microbial groups without inoculating the AMF. After four true leaves of the plant grow stably, 1mL (1X 10) of bacterial agent is inoculated to the root system of the plant⁷～1×10⁹CFU/mL). Culturing the plants in a greenhouse at 25 deg.C in the daytime and 15 deg.C at night under illumination for 18h/6h, watering every day to ensure that the plants grow in a state without water shortage, and harvesting after 2 months of plant growth.

Harvesting after 2 months of plant growth, taking out the plant together with rhizosphere soil, collecting the rhizosphere soil, and storing at-20 ℃; after the plants are taken out, 50g of soil samples are collected and put in a sealing bag to be naturally aired and stored in a soil airing frame for soil physical and chemical property determination; washing the plants with tap water, and washing with deionized water for 3-5 times; the cleaned plants are dried by absorbent paper and divided into roots and overground parts, the fresh weight of each part of the plants is weighed by a percentile scale (the result is shown in figure 1a), and the plant height was measured with a ruler, the plant root length was measured with a root scanner (Pro STD4800, Regent Instruments inc., canada) (results are shown in fig. 1b), 0.2g of fresh leaves of the plants were cut out and packed in a sealed bag and immediately placed in a-80 ℃ refrigerator for storage for determination of antioxidant enzyme activity (results are shown in fig. 3, determination of antioxidant enzyme activity was based on the principle and technique of plum symphysis biochemical experiment (2000), etc. (plum symphysis, plant physiology and biochemistry experiment, 2000: advanced education press), the rest of the aerial parts were packed in an envelope for deactivation of enzymes (105 ℃, 1h), oven-dried (60 ℃), and pulverized for determination of heavy metal content (results are shown in fig. 2, ICP-OES (Optima 5300DV, Perkin Elmer, USA)). After the root length of the plant is measured by a root system scanner, a plurality of sections (0.5-1 cm) of the radicle at different parts of the plant are cut and fixed in FAA fixing solution (5mL glacial acetic acid: 5mL formaldehyde: 90mL 50% ethanol) for 24h, and the method for mycorrhizal infection observation (Liu Run Yun Yin (2007) is referred to for mycorrhizal infection observation and the like (Liu Run Yin and Chengan, mycorrhizal science, scientific Press, 2007. Beijing.) is adopted, the plant root sections fixed for 24h by the FAA fixing solution (5mL glacial acetic acid: 5mL formaldehyde: 90mL 50% ethanol) are dyed, AMF is colored and then observed by a microscope, and the result is shown in Table 2), the residual root systems are dried by absorbent paper and arranged in a sealing bag for fixation, drying and crushing for heavy metal content measurement (the result is shown in figure 2, OE-S (Optima 5300DV, Perkin Elmer, USA)).

And (3) measuring the physical and chemical properties of the soil: and (3) measuring the pH of the soil, namely weighing 4g of air-dried soil sample which is sieved by a soil sieve with the diameter of 1mm (20 meshes) into a centrifuge tube, adding 10mL of distilled water (the liquid-soil ratio is 2.5:1), oscillating for 1h under the conditions of 25 ℃ and 160r/min, standing for 30min, taking supernatant, and measuring the pH of the soil by using a pH meter. Measuring the total amount of heavy metal in soil, weighing 0.2g (accurate to 0.0001g) of soil sample passing through a 100-mesh nylon sieve into a 100mL conical flask, adding 10mL of aqua regia (nitric acid: hydrochloric acid ═ 1:3) and 2.5mL of perchloric acid at 190 ℃, digesting until the solution is clear and transparent, evaporating the liquid, and measuring the total amount of heavy metal in the soilAnd (4) cooling after 1-2 mL of the dried solution is left, filtering, and fixing the volume to 25mL by using 5% nitric acid. And measuring the content of metal Cd in the filtrate by using ICP-OES. Effective state of heavy metals in soil, NH₄NO₃Extracting the metal effective state. Weighing 5g of soil sample passing through a 20-mesh nylon sieve into a 50mL centrifuge tube, and adding 25mL of 1mol/L NH₄NO₃Extracting the solution, performing shaking reaction at room temperature for 2h at 200r/min, centrifuging at 6000rpm and 25 deg.C for 20min, filtering, and determining metal content by ICP-OES. After planting, the concentrations of Cd in the soil in the experimental groups with the Cd concentrations of 0mg/kg and 50mg/kg are almost unchanged, and when the concentration of Cd is 100mg/kg, the content of Cd in the soil is remarkably reduced by treatment of the strain EG 16.

The experimental results are as follows:

1) as shown in FIGS. 1a to 1b, when the Cd concentration is 50mg/kg, the overground fresh weight of the sterilized strain EG16 (group 9) can be increased in other treatment groups, and the accelerating effect of Gm (group 8) on the overground fresh weight of the plant is strongest. All strain treatments produced a tendency to promote the fresh weight of the plants at a Cd concentration of 100mg/kg, with Gm (group 14) significantly increasing the fresh weight of the aerial parts and roots of the plants, and co-inoculation of strains EG16 and Gm (group 16) acting better than when both strains were inoculated separately.

2) As shown in fig. 2, co-inoculation of Gm with strains EG16, DJ3 (

groups

10, 16, 12, 18) resulted in significant increases in Cd concentration in the aerial parts and roots of the plants and significant reductions in heavy metal transfer coefficients (table 1). When the concentration of Cd is 100mg/kg, inoculating a strain DJ3 (group 17) to obviously reduce the concentration of Cd on the overground part and the root of the plant, and possibly changing the content of effective Cd in the soil under the action of the strain so as to inhibit the migration of heavy metals in the soil to the plant; gm (group 14), strain EG16 (group 15) and co-inoculation of the Gm and the strain EG16 (group 16) all lead the concentration of Cd at the roots of plants to be obviously increased, which shows that the root elongation can increase the capacity of the plants to absorb heavy metals; in addition, the transfer of the plant from the root to the overground part was significantly inhibited by the treatment with the sterilized strain DJ3 (group 17) (Table 1). Therefore, the inoculated strain can enable most heavy metals to be held in the root system of the plant, so that the potential risk of high-concentration Cd on edible parts of the crops is reduced.

TABLE 1 heavy metal transfer coefficient

Note: the data in the table are 3 parallel means + -standard deviation, significance analysis is carried out among the same Cd concentration, different letters indicate that significance difference is achieved among treatment groups, and p is less than 0.05.

3) As shown in fig. 3a to 3c, under Cd stress, compared to the non-inoculated group (CK), the inoculated strain decreased activities of superoxide dismutase (SOD), Catalase (CAT) and Peroxidase (POD) of the plant, which may be caused by the toxic effect of Cd relieved by the treatment of the inoculated strain; the co-inoculation effect of the saccaromyces mosseae Gm and the strain EG16 is most obvious when the concentration of Cd is 50mg/kg (group 10), and the corresponding plant biomass is the best at the concentration, which shows that the two strains can improve the activity of antioxidant enzyme through metabolic activity to relieve the poison of heavy metals to plants and further synergistically promote the growth of the plants.

4) The AMF forms mycorrhiza after infecting plant roots, can promote the absorption of water and nutrient (N, P) by the plant, and the secretion of the AMF can also promote the growth of the plant. As shown in table 2, strain DJ3 significantly promoted mycorrhizal infestation at each Cd concentration; the strain EG16 remarkably promotes mycorrhiza infection under Cd stress.

TABLE 2 mycorrhizal infection

Note: gm denotes glomus mosseae; the data in the table are mean ± standard deviation of 3 replicates, with different lower case letters indicating significant difference between Gm and Gm + EG16 treatment groups and different upper case letters indicating significant difference between Gm and Gm + DJ3 treatment groups, p < 0.05.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving cadmium resistance of tomatoes is characterized by comprising the following steps:

3) culturing tomatoes until they ripen and produce fruit;

the inoculation amount of the AMF microbial inoculum is 10-50 g/kg, and the AMF microbial inoculum is uniformly dispersed at a position 1-10 cm away from the surface layer of the soil;

the AMF microbial inoculum is a Moses sacculus mildew microbial inoculum; the Glomus mosseae is Glomus mossea;

the concentration of cadmium in the cadmium-polluted soil is 0-100 mg/kg;

the stable growth of the tomato seedlings refers to that the tomato seedlings grow into four true leaves;

the plant rhizosphere growth-promoting bacteria microbial inoculum comprises Enterobacter sp or Enterobacter ludwigii strain DJ 3;

the inoculation amount of the plant rhizosphere growth-promoting bacterium agent is 1 multiplied by 10⁶～1×10⁹CFU/kg, concentration of plant rhizosphere growth promoting bacteria agent is 1 multiplied by 10⁶～1×10⁹CFU/mL。

2. The method for improving cadmium tolerance of tomatoes according to claim 1, wherein 1-5 mL of the plant rhizosphere growth promoting bacterial agent is inoculated to a plant root system after four true leaves of the plant grow and grow stably.