Method for saline-alkaline-resistant screening and stress-resistant tissue culture seedling raising of bamboo reed

Abstract

The invention relates to the technical field of agricultural breeding, in particular to a bamboo reed saline-alkaline resistant screening and stress-resistant tissue culture seedling raising method which comprises the following steps: step 1, pretreatment; step 2, dynamic salt stress screening: placing the seed stems in a mixed salt-alkali solution with gradient increasing, culturing, measuring the bud length and root length growth rate of axillary buds of the seed stems, fitting a salt concentration-growth rate curve, and extracting a semi-inhibitory concentration IC50 and a maximum tolerance concentration MTC; step 3, salt tolerance grade classification; 4, carrying out stress-resistant tissue culture seedling culture: carrying out in-vitro culture on the axillary bud explant of the high-salt-resistant variety in a culture medium, and inducing clumpy buds and rooting in combination with a salt-resistant inducer; 5, domestication and transplanting: performing gradual salt stress domestication on the tissue culture seedlings, transplanting the tissue culture seedlings into a saline-alkaline environment, and monitoring the adaptability of the tissue culture seedlings in the saline-alkaline environment. According to the method disclosed by the invention, the efficient cultivation system of the suitable-to-grow bamboo reed seedlings in the saline-alkali soil is established by fusing dynamic stress response analysis and stress resistance phenotype directional strengthening technologies.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural breeding, and in particular to a method for screening saline-alkali tolerance and stress-resistant tissue culture seedlings of Phragmites australis. Background Art

[0002] As a perennial energy plant with both ecological restoration and resource utilization value, the salt-alkali tolerance of Phragmites australis is of great significance to salinized land management. Traditional Phragmites propagation relies on asexual reproduction, but in high-salt-alkali environments, problems such as inhibited axillary bud germination and poor root development lead to low transplant survival rates and limited restoration efficiency. Precision salt-alkali tolerance screening combined with stress-resistant tissue culture techniques can overcome the bottleneck of scarce saline-alkali land germplasm resources, enable large-scale production of high-quality seedlings, provide highly adaptable seed sources for saline-alkali land ecological restoration, and enhance the economic benefits of biomass resource development and utilization.

[0003] Existing studies, such as the document "Evaluation of Salt Tolerance of Axillary Buds of Phragmites during the Germination Period," mostly use static stress treatments with a single salt species, which cannot simulate the complex ion environment of real saline-alkali soil, resulting in deviations between screening results and field adaptability. Because traditional salt tolerance evaluations mostly rely on single morphological indicators such as germination rate and root length, and lack the support of dynamic growth response models, it is difficult to quantify the stress resistance threshold of varieties. Secondly, in the tissue culture seedling stage, existing technologies generally ignore the synergistic effect of light quality regulation and salt resistance inducers, resulting in weakened stress resistance characteristics of tissue culture seedlings. In addition, conventional acclimation methods lack a progressive salt concentration gradient design, resulting in the phenomenon of "environmental shock" after transplanting tissue culture seedlings. Therefore, a method for the tissue culture of Phragmites australis that is both salt-tolerant and stress-resistant is proposed. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method for screening salt-alkali tolerance and stress-resistant tissue culture seedlings of Phragmites australis. By integrating the technologies of dynamic stress response analysis and directional enhancement of stress resistance phenotype, an efficient cultivation system for Phragmites australis seedlings suitable for growing in saline-alkali land is established.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows: a method for screening salt-alkali tolerance and stress-resistant tissue culture seedlings of Phragmites australis, comprising the following steps:

[0006] Step 1, pretreatment: selecting a number of Phragmites australis stems as seed stems, cutting the stems of the seed stems with sterilized pruning shears, and then performing disinfection and bioactivation treatment;

[0007] Step 2: Dynamic salt stress screening: The seed stems were cultured in a mixed saline-alkali solution with increasing gradient, the axillary bud length and root length growth rate of the seed stems were measured, and the salt concentration-growth rate curve was fitted. The salt concentration-growth rate curve was fitted using a logistic model, and the formula was:

[0008]

[0009] Where y is the growth rate, c is the salt concentration, A, k and c0 are fitting parameters;

[0010] Extract half inhibitory concentration IC50 and maximum tolerated concentration MTC;

[0011] Step 3: Classification of salt tolerance: Based on IC50 and MTC values, the seed stems were divided into high salt tolerance, salt tolerance and salt sensitive types. High salt tolerance type has IC50 ≥ 180mmol·L -1 , MTC ≥ 200 mmol·L -1 , salt-tolerant type is 120mmol·L -1 ≤IC50<180mmol·L -1 , IC50 of salt-sensitive type is less than 120mmol·L -1 ;

[0012] Step 4: Stress-resistant tissue culture seedlings: axillary bud explants of highly salt-tolerant varieties are cultured in vitro in a culture medium, combined with a salt-resistant inducer to induce bud clustering and rooting;

[0013] Step 5: Acclimation and transplanting: After gradual salt stress acclimation, the tissue culture seedlings are transplanted into a saline-alkali environment, and the adaptability of the tissue culture seedlings in the saline-alkali environment is monitored.

[0014] Furthermore, in step 1, the selection criteria for Phragmites australis seed stems are: the stem diameter is ≥1.2 cm, the internode length is 5 to 8 cm, each seed stem contains ≥2 complete axillary buds, and the stem surface is free of disease spots, insect bites and mechanical damage.

[0015] Furthermore, in step one, the disinfection and bioactivation treatment includes: soaking the seed stems in a 1% potassium permanganate solution for 5 minutes, rinsing with clean water and then soaking for 30 minutes, soaking the disinfected seed stems in a mixture of 0.05% chitosan and 10 μM salicylic acid, and shaking culturing at 25° C. for 12 hours.

[0016] Furthermore, in step 2, the salt concentration of the gradient increase is specifically: the initial salt concentration is 50mmol·L -1 NaCl, increase by 50 mmol·L every 72 hours -1 The upper limit of salt concentration increase is 250mmol·L -1 , until the seed stem growth rate decreases by ≥90%.

[0017] Furthermore, in step 2, the mixed saline-alkali solution includes NaCl, Na2SO4 and NaHCO3 in a mass ratio of 3:1:1.

[0018] Furthermore, in step 4, the in vitro culture includes the following steps:

[0019] S11, explant preparation: take axillary buds of highly salt-tolerant Phragmites australis, sterilize the surface and remove the outer scales;

[0020] S12, primary culture, the explants were inoculated in a medium containing 1.5 mg·L 6-BA. -1 and NAA 0.1 mg·L -1 MS medium and cultured under light for 20 days;

[0021] S13, rooting induction: transfer to culture medium containing 0.8 mg·L IBA -1 The medium was diluted with 0.05% activated carbon in 1 / 2MS and cultured in the dark for 10 days, and then the light intensity was gradually increased.

[0022] Furthermore, in step 4, light quality regulation is used for rooting induction: 12 hours of 660nm, 2000lx red light irradiation is used daily in the primary culture stage; in the rooting stage, it is switched to 6 hours of red light daily and 6 hours of 450nm, 1500lx blue light irradiation alternately daily.

[0023] Furthermore, in step 4, the salt resistance inducer includes 50 μM betaine, 0.1 mg·L -1 Sodium silicate and silicon dioxide with a solution concentration of 0.05%, and a silicon dioxide particle size of ≤50nm.

[0024] Furthermore, in step five, gradual acclimation includes:

[0025] S21: Transplant tissue culture seedlings to a medium containing 50 mmol·L -1 The culture was carried out for 7 days in a medium containing NaCl, with a day-night temperature difference of 25°C and 15°C respectively;

[0026] S22: Increase the matrix salt concentration to 100 mmol·L -1 NaCl, culture for 7 days, add 0.05% humic acid;

[0027] S23: Increase the matrix salt concentration to 150 mmol·L -1 NaCl until the new leaves of the tissue culture seedlings unfold and the root length is ≥5 cm.

[0028] Furthermore, in step five, the adaptability standard of the tissue culture seedlings transplanted into a saline-alkali environment is: a survival rate of ≥80% in soil with a salt content of 0.3%, and a biomass loss rate of ≤15% 30 days after transplantation.

[0029] The above scheme has the following beneficial effects:

[0030] 1. This protocol significantly improves the initial stress resistance of seed stems through strict seed stem selection criteria, laying a solid foundation for subsequent salt stress screening. Compared to traditional single disinfection, this step enhances cell membrane stability through physiological regulation and increases axillary bud germination rate.

[0031] 2. This approach uses a gradient-increasing mixed saline-alkali solution to more realistically simulate the complex ionic environment of saline-alkali soils. Combined with a logistic model to dynamically fit the salt concentration-growth rate curve, it accurately extracts the half-inhibitory concentration and maximum tolerated concentration (MTC), enabling scientific quantification of salt tolerance and making screening results more field-compatible. A dual-parameter classification system based on IC50 and MTC categorizes varieties into highly salt-tolerant, salt-tolerant, and salt-sensitive types, avoiding misjudgment based on a single indicator. Classification results directly guide the selection of subsequent tissue culture seedlings, improving the efficiency of breeding stress-resistant varieties.

[0032] 3. This protocol, through modified MS medium, mitigates salt stress damage through osmotic regulation and cell wall strengthening. Light quality control (alternating red and blue light) specifically promotes bud differentiation and root development, shortening the rooting cycle. The synergistic application of chemical and physical methods significantly enhances the saline-alkali adaptability of tissue culture seedlings.

[0033] 4. This program, through phased acclimatization with increasing salt concentrations and supplemented with humic acid, gradually enhances the salt tolerance threshold of tissue culture seedlings and mitigates ion toxicity. Post-transplant adaptability standards ensure a smooth transition from the laboratory to saline-alkali land, achieving the dual goals of ecological restoration and economic benefits.

[0034] 5. This plan optimizes material quality through pretreatment, provides scientific data through dynamic screening, guides precise breeding through classification, enhances stress resistance through tissue culture, and ensures field adaptability through domestication. This multi-step synergy overcomes the fragmented and inefficient limitations of traditional methods, forming a highly efficient and scalable system for screening for saline-alkali tolerance and cultivating stress-resistant tissue-based seedlings in Phragmites australis.

[0035] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a schematic diagram of the steps of an embodiment of the method for screening salt-alkali tolerance and stress-resistant tissue culture seedlings of Phragmites australis. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0040] The following is further described in detail through specific implementation methods:

[0041] Example:

[0042] As attached Figure 1 A method for screening salt-alkali tolerance and stress-resistant tissue culture seedlings of Phragmites australis comprises the following steps:

[0043] Step 1, pretreatment: select a number of Phragmites australis stems as seed stems, and the selection criteria of the Phragmites australis seed stems are: the stem diameter is ≥1.2cm, the internode length is 5-8cm, each seed stem contains ≥2 complete axillary buds, and the stem surface is free of disease spots, insect bites and mechanical damage. After cutting the stems of the seed stems with sterilized pruning shears, the seed stems are immersed in 1% potassium permanganate solution for 5 minutes, rinsed with clean water and then immersed for 30 minutes. The sterilized seed stems are immersed in a mixed solution containing 0.05% chitosan and 10μM salicylic acid, and cultured with shaking at 25°C for 12 hours.

[0044] Step 2: Dynamic salt stress screening: The seed stems were cultured in a mixed saline-alkali solution with increasing gradient. The mixed saline-alkali solution included NaCl, Na2SO4 and NaHCO3 in a mass ratio of 3:1:1. The specific increasing salt concentration was as follows: initial salt concentration 50 mmol·L -1 NaCl, increase by 50 mmol·L every 72 hours -1 The upper limit of salt concentration increase is 250mmol·L -1, until the stem growth rate dropped by ≥90%, the axillary bud length and root length growth rate of the stem were measured, and the salt concentration-growth rate curve was fitted. The salt concentration-growth rate curve was fitted using the Logistic model, and the formula was:

[0045]

[0046] Among them, y is the growth rate, c is the salt concentration, A is the maximum growth rate, k is the stress sensitivity, and c0 is the salt concentration corresponding to the midpoint of the growth rate decrease, that is, the half-inhibitory concentration IC50; the IC50 and the maximum tolerance concentration MTC of the stem are extracted through the salt concentration-growth curve.

[0047] Step 3: Classification of salt tolerance: Based on IC50 and MTC values, the seed stems were divided into high salt tolerance, salt tolerance and salt sensitive types. High salt tolerance type has IC50 ≥ 180mmol·L -1 , MTC ≥ 200 mmol·L -1 , salt-tolerant type is 120mmol·L -1 ≤IC50<180mmol·L -1 , IC50 of salt-sensitive type is less than 120mmol·L -1 .

[0048] Step 4: Stress-resistant tissue culture seedlings: axillary bud explants of highly salt-tolerant varieties are cultured in vitro in a culture medium. The in vitro culture includes the following steps:

[0049] S11, explant preparation: take axillary buds of highly salt-tolerant Phragmites australis, sterilize the surface and remove the outer scales;

[0050] S12, primary culture, the explants were inoculated in a medium containing 1.5 mg·L 6-BA. -1 and NAA 0.1 mg·L -1 MS medium and cultured under light for 20 days;

[0051] S13, rooting induction: transfer to culture medium containing 0.8 mg·L IBA -1 The medium was diluted with 0.05% activated carbon in 1 / 2MS and cultured in the dark for 10 days, and then the light intensity was gradually increased.

[0052] Combined with salt resistance inducers, including 50μM betaine, 0.1mg·L -1 Sodium silicate and a solution concentration of 0.05% silica, with a silica particle size of ≤50nm, are used to induce bud clustering and rooting. Rooting induction is regulated by light quality: in the primary culture stage, 660nm, 2000lx red light is used for 12 hours per day; in the rooting stage, it is switched to 6 hours of red light per day and 6 hours of 450nm, 1500lx blue light per day, alternating irradiation.

[0053] Step 5: Acclimation and transplanting: After gradual salt stress acclimation, the tissue culture seedlings are transplanted into a saline-alkali environment. Gradual acclimation includes:

[0054] S21: Transplant tissue culture seedlings to a medium containing 50 mmol·L -1 The culture was carried out for 7 days in a medium containing NaCl, with a day-night temperature difference of 25°C and 15°C respectively;

[0055] S22: Increase the matrix salt concentration to 100 mmol·L -1 NaCl, culture for 7 days, add 0.05% humic acid;

[0056] S23: Increase the matrix salt concentration to 150 mmol·L -1 NaCl was added until the new leaves of the tissue culture seedlings unfolded and the root length was ≥5cm, and the adaptability of the tissue culture seedlings in the saline-alkali environment was monitored. The adaptability standards of the tissue culture seedlings transplanted into the saline-alkali environment were: the survival rate was ≥80% in the soil with a salt content of 0.3%, and the biomass loss rate was ≤15% 30 days after transplanting.

[0057] The specific implementation process is as follows:

[0058] 1. Pretreatment optimization experiment

[0059] 1. Material processing: Select healthy Phragmites australis stalks and process them according to the following scheme:

[0060] Experimental group: 1% potassium permanganate immersion for 5 min → 0.05% chitosan + 10 μM salicylic acid shaking culture for 12 h;

[0061] Control group: soak in 1% potassium permanganate for 5 minutes → re-immerse in clean water for 30 minutes;

[0062] 2. Experimental results:

[0063] Experimental group: axillary bud enlargement rate ≥90%;

[0064] Control group: axillary bud enlargement rate ≤ 60%;

[0065] 3. Conclusion: The experimental group activated the stress resistance pathway through chitosan and salicylic acid, enhanced cell membrane stability, and significantly improved axillary bud activity.

[0066] 2. Salt stress screening experiment:

[0067] 1. Material treatment: 40 Phragmites australis stems were selected and divided into an experimental group and a control group, and treated according to the following scheme:

[0068] Experimental group: Cultured in a gradient-increasing mixed saline-alkali solution, NaCl: Na2SO4: NaHCO3 = 3:1:1, with an initial salt concentration of 50 mmol·L-1 NaCl, increase by 50 mmol·L every 72 hours -1 , until the seed stem growth rate decreases by ≥90% or the salt concentration increases to an upper limit of 250mmol·L -1 ;

[0069] Control group: single 150mmol·L -1 NaCl stress;

[0070] 2. Measurement indicators:

[0071] Determine the shoot and root lengths of Phragmites australis stems under current salt concentrations;

[0072] 3. Experimental results:

[0073]

[0074] 4. Conclusion: The experimental group simulated the real environment by gradient mixing of salt and alkali, and the IC50 (IC50 of the experimental group = 180mmol·L -1 , control group IC50=120mmol·L -1 ), significantly improving the screening accuracy.

[0075] 3. Stress-resistant tissue culture seedling experiment

[0076] 1. Material treatment: 20 explants of each type of high salt-tolerant variety cultivated in steps 1 to 3 were selected for in vitro culture and divided into a control group and an experimental group. The treatment was carried out according to the following scheme:

[0077] Experimental group: 50 μM betaine, 0.1 mg·L -1 Sodium silicate and a 0.05% silica solution were used as salt-resistance inducers. During the primary culture stage, irradiation was performed with 660nm, 2000lx red light for 12 hours per day. During the rooting stage, irradiation was switched to alternating 6 hours of red light per day and 6 hours of 450nm, 1500lx blue light per day.

[0078] Control group: fixed white light irradiation for 12 hours per day in basic MS medium;

[0079] 2. Experimental results:

[0080]

[0081] 3. Conclusion: The experimental group significantly improved the salt resistance of tissue culture seedlings by adding betaine and nano-silica, combined with light quality regulation; the improved light culture shortened the rooting time and improved the root quality.

[0082] 4. Acclimation and transplanting experiment:

[0083] 1. Acclimation plan: 20 rooted experimental group tissue culture seedlings from Experiment 3 were selected and divided into an experimental group and a control group, and treated according to the following plan:

[0084] Experimental group: After gradual salt stress in step 5, the plants were transplanted to a 0.3% saline-alkali environment;

[0085] Control group: directly transplanted into 0.3% saline-alkali soil;

[0086] 2. Observation indicators: survival rate and biological loss rate 30 days after transplanting;

[0087] 3. Experimental results:

[0088]

[0089] 4. Conclusion: Gradual acclimation increased the survival rate of tissue culture seedlings by 105% and reduced biomass loss by 67.7%.

[0090] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for screening salt-alkali tolerance and stress resistance tissue culture seedling of Phragmites australis, characterized in that: The following steps are involved: Step 1, pretreatment: selecting a number of Phragmites australis stems as seed stems, cutting the stems of the seed stems with sterilized pruning shears, and then performing disinfection and bioactivation treatment; Step 2: Dynamic salt stress screening: The seed stems were cultured in a mixed saline-alkali solution with increasing gradient, the axillary bud length and root length growth rate of the seed stems were measured, and the salt concentration-growth rate curve was fitted. The salt concentration-growth rate curve was fitted using a logistic model, and the formula was: Where y is the growth rate, c is the salt concentration, A is the maximum growth rate, k is the stress sensitivity, and c0 is the salt concentration corresponding to the midpoint of the growth rate decrease, that is, the half-inhibitory concentration IC50; IC50 and the maximum tolerance concentration (MTC) of the stem were extracted from the salt concentration-growth curve; Step 3: Classification of salt tolerance: Based on IC50 and MTC values, the seed stems were divided into high salt tolerance, salt tolerance and salt sensitive types. High salt tolerance type has IC50 ≥ 180mmol·L -1 , MTC ≥ 200 mmol·L -1 , salt-tolerant type is 120mmol·L -1 ≤IC50<180mmol·L -1 , IC50 of salt-sensitive type is less than 120mmol·L -1 ; Step 4: Stress-resistant tissue culture seedlings: axillary bud explants of highly salt-tolerant varieties are cultured in vitro in a culture medium, combined with a salt-resistant inducer to induce bud clustering and rooting; Step 5: Acclimation and transplanting: After gradual salt stress acclimation, the tissue culture seedlings are transplanted into a saline-alkali environment, and the adaptability of the tissue culture seedlings in the saline-alkali environment is monitored.

2. The method for screening saline-alkali tolerance and stress resistance tissue culture of Phragmites australis according to claim 1, wherein In step 1, the selection criteria for Phragmites australis seed stems are: stem diameter ≥ 1.2 cm, internode length 5-8 cm, each seed stem section contains ≥ 2 complete axillary buds, and the stem surface is free of disease spots, insect bites and mechanical damage.

3. the method for screening salt-alkali tolerance and stress resistance tissue culture seedling of Phragmites australis according to claim 2, is characterized in that, In step 1, the disinfection and bioactivation treatment includes: soaking the seed stems in 1% potassium permanganate solution for 5 minutes, rinsing with clean water and then soaking for 30 minutes, soaking the disinfected seed stems in a mixture of 0.05% chitosan and 10 μM salicylic acid, and shaking culturing at 25° C. for 12 hours.

4. The method for screening saline-alkali tolerance and stress resistance tissue culture of Phragmites australis according to claim 3, wherein In step 2, the salt concentration of the gradient increase is as follows: initial salt concentration 50 mmol·L -1 NaCl, increase by 50 mmol·L every 72 hours -1 The upper limit of salt concentration increase is 250mmol·L -1 , until the seed stem growth rate decreases by ≥90%.

5. The method for screening salt-alkali tolerance and stress resistance tissue culture of Phragmites australis according to claim 4, wherein In step 2, the mixed saline-alkali solution includes NaCl, Na2SO4 and NaHCO3 in a mass ratio of 3:1:

1.

6. The method for screening salt-alkali tolerance and stress resistance tissue culture seedling of Phragmites australis according to claim 5, wherein In step 4, the in vitro culture includes the following steps: S11, explant preparation: take axillary buds of highly salt-tolerant Phragmites australis, sterilize the surface and remove the outer scales; S12, primary culture, the explants were inoculated in a medium containing 1.5 mg·L 6-BA. -1 and NAA 0.1 mg·L -1 MS medium and cultured under light for 20 days; S13, rooting induction: transfer to culture medium containing 0.8 mg·L IBA -1 The medium was diluted with 0.05% activated carbon in 1 / 2MS and cultured in the dark for 10 days, and then the light intensity was gradually increased.

7. The method for screening salt-alkali tolerance and stress resistance tissue culture of Phragmites australis according to claim 6, wherein: In step 4, light quality regulation is used for rooting induction: 12 hours of 660nm, 2000lx red light irradiation per day is used in the primary culture stage; in the rooting stage, it is switched to 6 hours of red light per day and 6 hours of 450nm, 1500lx blue light irradiation per day.

8. The method for screening salt-alkali tolerance and stress resistance tissue culture seedling of Phragmites australis according to claim 7, wherein In step 4, the salt resistance inducer includes 50 μM betaine, 0.1 mg·L -1 Sodium silicate and silicon dioxide with a solution concentration of 0.05%, and a silicon dioxide particle size of ≤50nm.

9. The method for screening salt-alkali tolerance and stress resistance tissue culture seedling of Phragmites australis according to claim 8, wherein In step five, gradual acclimation includes: S21: Transplant tissue culture seedlings to a medium containing 50 mmol·L -1 The culture was carried out for 7 days in a medium containing NaCl, with a day-night temperature difference of 25°C and 15°C respectively; S22: Increase the matrix salt concentration to 100 mmol·L -1 NaCl, culture for 7 days, add 0.05% humic acid; S23: Increase the matrix salt concentration to 150 mmol·L -1 NaCl until the new leaves of the tissue culture seedlings unfold and the root length is ≥5 cm.

10. The method for screening salt-alkali tolerance and stress resistance tissue culture seedling of Phragmites australis according to claim 9, characterized in that: In step 5, the adaptability standard of the tissue culture seedlings transplanted into the saline-alkali environment is: the survival rate in the soil with a salt content of 0.3% is ≥ 80%, and the biomass loss rate ≤ 15% 30 days after transplantation.

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