A method for improving the heat resistance of rhododendrons by utilizing the synergistic effect of Indian piriformis and magnesium.

Abstract

This invention discloses a method for improving the heat resistance of rhododendrons by utilizing the synergistic effect of *Pyrhododendron indicum* and magnesium. The method includes: applying a solid culture of *Pyrhododendron indicum* to the soil around the rhododendron roots; then applying *Pyrhododendron indicum* liquid bacterial solution twice to the soil around the rhododendron roots at a rate of 50 ml per 10 days; then applying MgSO4·7H2O twice to the soil around the rhododendron roots, with an interval of 5 days between each application; then cultivating the rhododendrons under initial high-temperature stress; then gradually increasing the stress temperature according to preset conditions until the target high-temperature stress temperature is reached; during the high-temperature stress process, applying MgSO4·7H2O and *Pyrhododendron indicum* liquid bacterial solution according to preset conditions; and finally, selecting rhododendrons with improved heat resistance according to preset conditions. This method can improve the heat resistance of rhododendrons, improve their growth under heat stress, promote the wider application of rhododendrons in landscaping, provide a scientific basis for the cultivation and management of rhododendrons, improve their growth performance under high-temperature environments, and promote the sustainable development of garden plants.

Description

Technical Field

[0001] This invention relates to the fields of rhododendron cultivation technology and horticultural crop protection technology, and in particular to a method for improving the heat resistance of rhododendrons by utilizing the synergistic effect of Indian piriformis and magnesium. Background Technology

[0002] Rhododendrons are a globally widespread and diverse plant group, with over 1000 known species. Due to their unique ornamental value and important role in the ecosystem, rhododendrons are highly valued in horticulture and ecological research. However, most wild rhododendron species prefer humid, cool climates and are intolerant of high temperatures, with an optimal growth temperature of 18°C ​​to 25°C. Against the backdrop of global warming and frequent extreme heat waves, the introduction and cultivation of rhododendrons face significant challenges. Extreme heat can easily cause rhododendron leaves to yellow, dry out, and even die, severely hindering their widespread planting and utilization in southern regions. Therefore, improving the heat tolerance of rhododendrons and cultivating more heat-resistant varieties is of significant practical importance and long-term impact for promoting the introduction, cultivation, and utilization of rhododendrons in medium- and high-temperature regions and enhancing the resilience of the horticultural industry.

[0003] Among the many methods for improving the heat tolerance of azaleas, *Piriformospora indica* is a promising endophytic fungus. This fungus can colonize the roots of various plants, promoting plant growth, accelerating the absorption of minerals such as nitrogen and phosphorus, improving plant tolerance to abiotic stress, and inducing systemic resistance. *Piriformospora indica* can be cultured on artificial media, greatly facilitating research on its interactions with plants and potentially leading to widespread applications in agriculture, forestry, and floriculture. However, azalea growth depends on acidic soil environments, a characteristic that presents a challenge when applying *Piriformospora indica*. This is because the culture medium and pH conditions are often chosen to be acidic during the preparation of *Piriformospora indica*, allowing it to better adapt and function. However, in acidic environments, magnesium ion loss is exacerbated, and magnesium is an essential nutrient element for plant growth, participating in chlorophyll synthesis, photosynthesis, protein synthesis, energy metabolism, and various enzymatic reactions. Magnesium deficiency severely affects the growth and stress resistance of azaleas.

[0004] Currently, there is a lack of comprehensive applications and technologies on the market for combining Indian piriformis and magnesium to improve the heat resistance of azaleas. Therefore, exploring how to improve the heat resistance of azaleas by combining their growth characteristics and cultivation needs is a research topic with positive and practical significance. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a reliable, flexible, and effective method for improving the heat resistance of rhododendrons by utilizing the synergistic effect of Indian piriformis and magnesium.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is as follows:

[0007] A method for improving the heat resistance of rhododendrons by utilizing the synergistic effect of *Pyrrosia lingua* and magnesium, comprising:

[0008] Solid culture of *Pyrhodops praecox* was applied to the soil around the rhododendron roots. Then, at a time interval of 10 days, 50 ml of *Pyrhodops praecox* liquid was applied twice to the soil around the rhododendron roots. After the last application of *Pyrhodops praecox* liquid, MgSO4·7H2O was applied twice to the soil around the rhododendron roots, with an interval of 5 days between each application. The rhododendrons were then cultivated under the initial high-temperature stress temperature. The high-temperature stress temperature was then gradually increased according to the preset conditions until the target high-temperature stress temperature was reached. During the high-temperature stress process, MgSO4·7H2O and *Pyrhodops praecox* liquid were applied according to the preset conditions. Finally, rhododendrons with improved heat resistance were selected according to the preset conditions.

[0009] As one possible implementation, the method for preparing the solid culture of *Pyrrosia lingua* described in this scheme further includes:

[0010] Prepare a culture solution containing the following components at a final concentration of 6.0 g·L⁻¹. -1 Potato starch, 20.0 g·L -1 Glucose, 20.0 g·L -1 Agar, 6.0 g·L -1 Coconut water and 0.1 mg·L -1 Indoleacetic acid (IAA);

[0011] The culture solution was sterilized at 121°C for 20 minutes, and its pH was adjusted to 5.5.

[0012] Using a 200L pipette tip, cut a 0.5cm Pi mycelium block, invert it and place it in a culture medium plate containing the culture solution. Then, incubate it at 28℃ in the dark for 14 days until the mycelium grows to 8cm. A solid culture containing Piero spore mycelium and spore aggregates is obtained, which is the Piero spore solid culture.

[0013] As a preferred implementation option, the method for preparing the liquid culture of *Pyrrosia lingua* described in this scheme preferably includes:

[0014] Prepare a culture solution containing the following components at a final concentration of 6.0 g·L⁻¹. -1 Potato starch, 20.0 g·L⁻¹ glucose, 2.0 g·L⁻¹ -1 Corn steep liquor and 0.1 mg·L -1 Cytokinin CK;

[0015] The culture solution was sterilized at 121°C for 20 minutes, and its pH was adjusted to 5.5.

[0016] Cut a 0.5cm solid culture block of *Pyrrosia indicum* and place it in a culture container containing culture solution. Then place the container on a shaker and culture it in the dark at 28℃ and 160r / min for 15 days to obtain a liquid culture of *Pyrrosia indicum*.

[0017] As a preferred implementation option, this method involves applying MgSO4·7H2O twice to the soil around the rhododendron roots, with each application being 20 ml at a concentration of 2 mmol·L⁻¹. -1 .

[0018] As a preferred implementation option, the initial high-temperature stress temperature described in this scheme is preferably 30°C, and the target high-temperature stress temperature is 35°C.

[0019] As a preferred implementation option, the preferred method for subjecting azaleas to high-temperature stress includes:

[0020] The azaleas were cultivated under an initial high-temperature stress temperature of 30℃. When no abnormal growth was observed, the high-temperature stress temperature was gradually increased by 1-2℃ per week until the target high-temperature stress temperature of 35℃ was reached.

[0021] As a preferred implementation option, this scheme adjusts the high temperature stress temperature according to temperature steps of 30-32℃, 32-34℃, and 34-35℃ when the azaleas show no abnormal growth under high temperature stress.

[0022] Each time the high temperature stress temperature was adjusted, MgSO4·7H2O and Indian piriformis liquid bacterial solution were applied according to the standard amount within the preset temperature range.

[0023] The standard volume for a temperature gradient range of 30-32℃ is: 20 ml of solution with a concentration of 2 mmol·L⁻¹. -1 MgSO4·7H2O, 50ml of Indian piriformis liquid culture;

[0024] The standard amount for a temperature gradient range of 32-34℃ is: 30 ml of solution with a concentration of 3 mmol·L⁻¹. -1 MgSO4·7H2O, 60ml of Indian piriformis liquid culture;

[0025] The standard volume for a temperature gradient range of 34-35℃ is: 40 ml with a concentration of 4 mmol·L⁻¹. -1 MgSO4·7H2O, 70ml of Indian piriformis liquid culture.

[0026] As a preferred implementation option, this scheme stipulates that when azaleas exhibit abnormal growth under high temperature stress, the heating should be stopped and the current temperature period extended to 10 days. At the same time, MgSO4·7H2O and Indian piriformis liquid bacterial solution should be applied at 50% of the standard amount for the corresponding temperature range, and the recovery of the plants should be observed.

[0027] Once the azaleas have resumed normal growth after 10 days, the temperature will continue to rise until the next high-temperature stress temperature is reached.

[0028] If the azalea does not resume normal growth after 10 days, maintain the current temperature and do not raise it further until the plant has fully recovered.

[0029] Based on the above, the method proposed in this scheme to improve the heat resistance of rhododendrons by utilizing the synergistic effect of Indian piriformis and magnesium can be summarized as follows:

[0030] S1. Solid culture of *Pyrrosia lingua*: Using potato dextrose agar (PDA), the solid PDA was prepared into a solution (i.e., culture solution), sterilized at 121°C for 20 minutes, and the pH was adjusted to 5.5. The potato dextrose agar (PDA) medium contained the following components at a final concentration of 6.0 g·L⁻¹. -1 Potato starch, 20.0 g·L -1 Glucose, 20.0 g·L -1 Agar, 6.0 g·L -1 Coconut water and 0.1 mg·L -1 Indoleacetic acid (IAA); using a 200L pipette tip, cut 0.5cm *Pi* mycelial blocks, inverted them onto a culture medium plate containing the culture solution, and then incubate at 28°C in the dark for 14 days until the mycelium grows to 8cm, obtaining a solid culture containing *Pi* mycelium and spore aggregates, i.e., *Pi* solid culture; this solid culture will be used for subsequent mycelial culture and direct application for colonization of plant roots; 6.0 g·L⁻¹ is added to the formulation. -1 Coconut water and 0.1 mg·L -1 Indoleacetic acid (IAA) helps promote the mycelial growth of *Pyrhodotorula lataniae*.

[0031] S2. Liquid culture of *Pyrrosia lingua*: Potato dextrose agar (PDB) was used. The PDB solution was prepared, sterilized at 121°C for 25 minutes, and the pH was adjusted to 5.5. The PDB agar formulation contained the following components at a final concentration of 6.0 g / L. -1 Potato starch, 20.0 g·L -1 Glucose, 2.0 g·L -1 Corn steep liquor and 0.1 mg·L -1Cytokinin (CK) was used. From a solid culture already cultured on PDA medium (i.e., *Pyrrosia indicum* solid culture), a piece (Φ = 0.5 mm) was cut and added to an Erlenmeyer flask containing PDB medium. The flask was then incubated in the dark at 28°C with shaking (160 r / min) for 15 days to prepare a liquid culture containing a large number of *Pyrrosia indicum* spores and hyphae. The PDB medium contained 2.0 g·L⁻¹ cytokinin. -1 Corn steep liquor and 0.1 mg·L -1 The purpose of cytokinin (CK) is to further promote the growth of bacteria in the bacterial solution, which will be used for application to plant roots in subsequent steps.

[0032] S3. Staged application of solid culture and liquid bacterial solution: One month before the onset of high temperature stress, the prepared solid culture and liquid bacterial solution of *Pyrhododendron indicum* were applied to the soil around the roots in stages. Specifically: (1) 10g of solid culture was applied to the roots of azaleas to form a stable mycelial network and promote early colonization; (2) 50ml of liquid bacterial solution of *Pyrhododendron indicum* was applied to the roots of azaleas every 10 days for two consecutive applications. The design of this method is based on the fact that the high concentration of mycelial network of solid culture can quickly make physical contact with the plant roots and promote rapid colonization of mycelium; while the liquid bacterial solution is evenly distributed around the roots through permeability, further consolidating and expanding the colonization effect and ensuring the long-term existence and activity of *Pyrhododendron indicum* in the roots.

[0033] S4. Magnesium synergistic application: Five days after the last application of Indian piriformis liquid bacterial solution to the rhododendron roots, take 20 ml of a solution with a concentration of 2 mmol·L⁻¹. -1 The MgSO4·7H2O solution was applied to the soil around the roots twice, with a 5-day interval between the second application.

[0034] S5. Gradual Adaptation Method: By gradually increasing high-temperature stress and adjusting the application dosage in stages, additional magnesium solution and bacterial solution are applied to the plants at each temperature stage to provide continuous support and protection, ensuring that the plants maintain healthy metabolic functions and symbiotic relationships under high temperatures. Initial high-temperature stress begins at 30℃ and gradually increases to 35℃, increasing by 2℃ each week until the plants adapt to the target temperature. During this process, the application dosage is adjusted. If abnormal reactions occur (such as yellowing or wilting of leaves), the temperature increase is stopped, and the current temperature stage is extended to 10 days. Simultaneously, the application dosage is reduced to 50% of the normal application standard, and the plant's recovery is observed.

[0035] (1) If the azaleas recover to normal after 10 days, the temperature can be raised further.

[0036] (2) If recovery is slow (no return to normal growth after 10 days), maintain the current temperature without further heating until the plant fully recovers. If it recovers to normal after 10 days, the temperature can be increased. If recovery is slow, maintain the current temperature without further heating until the plant fully recovers. If the plant still has not recovered after the extended observation period, simply maintain the ambient temperature at around 30℃ and do not continue to increase the temperature.

[0037] In particular, the improved initial high-temperature stress described in S5 starts at 30°C and gradually increases to 35°C, increasing by 1-2°C per week until the target temperature is met.

[0038] As an example of an ideal scenario, the specific steps for adjusting the applicable amount in this process are as follows:

[0039] During the 30℃ to 32℃ period: administer 20ml once at a concentration of 2mmol·L⁻¹. -1 A solution of MgSO4·7H2O and 50 ml of Pyridis oryzae solution were used to maintain the temperature for 7 days to help the plant adapt to the initial high temperature stress.

[0040] During the 32℃ to 34℃ period: administer 30ml once at a concentration of 3mmol·L⁻¹. -1 A solution of MgSO4·7H2O and 60 ml of Pyridis oryzae solution were used, and the temperature was maintained for 7 days to help plants enhance the synergistic effect between roots and fungi at higher temperatures.

[0041] During the 34℃ to 35℃ period: administer 40ml once at a concentration of 4mmol·L⁻¹. -1 A solution of MgSO4·7H2O and 70 ml of Pyridis oryzae solution were used to maintain the temperature for 7 days to ensure that the plant could maintain stable metabolism and stress resistance under extreme high temperatures.

[0042] Based on the above, this solution also provides a method for cultivating heat-resistant rhododendrons, which is obtained by the method described above.

[0043] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0044] (1) In the process of cultivating azaleas, the application of Indian pyriformis liquid and Indian pyriformis solid culture can significantly alleviate the symptoms of wilting and yellowing of azalea leaves under high temperature stress. This scheme promotes the growth of new shoots of azaleas, increases the fresh weight of the underground parts of azaleas, improves the antioxidant capacity of azaleas under high temperature stress, and helps azaleas maintain protein stability under high temperature stress.

[0045] (2) This scheme effectively improved the growth and efficacy of Indian piriformis by improving the culture medium formula and adding enhancers (coconut water, IAA, corn steep liquor, CK);

[0046] (3) In the process of cultivating azaleas, magnesium-containing substances are added to the azalea cultivation process so that the growth of azaleas in acidic soil can be improved under the synergistic effect.

[0047] (4) This scheme adopts a gradual adaptation method to enable azaleas to gradually adapt to the high temperature environment under high temperature stress, providing an operable high temperature resistance strategy.

[0048] (5) The fungus used in this scheme is Indian piriformis, which can be cultured on artificial culture medium, does not require a live host, is easy to prepare on a large scale, and has no adverse effects on soil and environment. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a comparative illustration of the biophenotypes of rhododendrons in this embodiment and the control group.

[0051] Figure 2 This is a statistical comparison of the control and implementation examples of this scheme in terms of rhododendron leaves and plant height.

[0052] Figure 3 This is a comparison of the biomass of rhododendrons in this embodiment and the control group. Rhododendrons under high temperature stress showed better new shoot growth and increased stem diameter; the fresh weight, including both above-ground and underground parts, was also greater.

[0053] Figure 4 This is a comparison of the antioxidant capacity of azalea leaves and roots between the embodiments of this scheme and the control group;

[0054] Figure 5 This is a comparison between the embodiments of this scheme and the control group in terms of maintaining or reducing the content of soluble protein in rhododendrons. Detailed Implementation

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] Unless otherwise specified, the materials and equipment used in the embodiments of the present invention can be purchased on the market.

[0057] 1.1 Test Materials

[0058] 1.1.1 Plant materials

[0059] This experiment used Hainan azalea as the research object, and all materials used were purchased from Jinhua Yonggen Azalea Cultivation Co., Ltd.

[0060] Healthy, disease-free, and highly uniform azalea seedlings were selected and planted in 14cm-deep plastic pots. The seedlings were approximately 20-30cm tall. All cultivation substrates used for the azaleas were peat moss and vermiculite in a 2:1 (VV) ratio. The azaleas were placed in the same artificial climate chamber and cultivated under identical environmental parameters: 2000 lx light intensity, 12 hours of daylight, 25°C temperature, and 60% humidity.

[0061] 1.1.2 Preparation of solid culture and bacterial suspension of *Pyrhodotorula latae*

[0062] The Indian piriformis strain was obtained from Fujian Agriculture and Forestry University.

[0063] Solid culture of *Pyrhodotorula praecox*: Potato dextrose agar (PDA) medium, with the composition shown in Table 1, was used. After preparation, the solution was sterilized at 121°C for 20 min, and the pH was adjusted to 5.5. *Pyrhodotorula praecox* mycelial blocks with a diameter of 0.5 cm were cut using a 200L pipette tip, inverted, and placed in PDA medium plates. The plates were incubated in the dark at 28°C for 14 days until the mycelium reached a diameter of 8 cm, yielding a solid culture containing *Pyrhodotorula praecox* mycelium and spore aggregates. This solid culture will be used for subsequent spirulina culture and direct application for colonization of plant roots.

[0064] Table 1. Potato Dextrose Agar Medium Formula

[0065]

[0066] Liquid culture of *Pyrophorus indicus*: A modified potato dextrose (PDB) medium was used, comprising 6.0 g·L⁻¹. -1 Potato starch, 20.0 g·L -1 Glucose, 2.0 g·L -1 Corn steep liquor and 0.1 mg·L -1Cytokinin (CK) was prepared into a solution and sterilized at 121°C for 25 min, with the pH adjusted to 5.5. A 0.5 mm section of the culture was cut from the solid culture already cultured on PDA medium and added to an Erlenmeyer flask containing PDB medium. The flask was then placed in a shaker at 28°C and incubated in the dark (160 rpm) for 15 days to prepare a stock solution containing a large amount of *Pyrrosia indicum* for later use.

[0067] 1.2 Test Methods

[0068] The experiment was conducted at the International Magnesium Institute of Fujian Agriculture and Forestry University from February to May 2024. Two temperature levels were set up: 25℃ / 22℃ (CK, day / night: 14h / 10h) and 38℃ / 30℃ (PIHS, day / night: 144h / 10h). At each temperature level, one inoculation treatment and one control were set up: control group (CK, room temperature, no inoculation with Indian pyriformis), high temperature stress control group (CKHS, high temperature stress, no inoculation with Indian pyriformis), room temperature inoculation with Indian pyriformis and magnesium group (PI+Mg), and high temperature inoculation with Indian pyriformis and magnesium group (PIHS+Mg). A total of 4 treatments were randomly arranged, with 4 biological replicates for each treatment.

[0069] The specific procedure for the room-temperature group inoculated with Indian pear cells and magnesium was as follows: The prepared solid culture of *Pyrrosia lingua* and liquid bacterial solution were evenly poured into the soil around the roots. First, the solid culture (10g per rhododendron root) was applied to the roots, followed by 50ml of liquid bacterial solution. This was repeated twice, once every 10 days. Five days after the last pour, 20ml of a 2mmol·L⁻¹ solution was collected. -1 The MgSO4·7H2O solution was applied to the soil around the roots twice, with the second application 5 days apart, for a total of 30 days.

[0070] For the culture of *Pyrrosia lingua* and magnesium (PIHS+Mg) inoculated at high temperatures, the initial process was the same as that of the normal temperature group. Subsequent high-temperature stress treatment involved gradually increasing the high-temperature stress and adjusting the application dosage to allow the rhododendrons to adapt to the high-temperature environment in advance. The initial high temperature started at 30°C, gradually increasing to 35°C, increasing by 2°C each week, and finally increasing by 1°C in the last week until the target temperature was met. Regarding material application, it included: During the 30°C to 32°C stage: a single application of 20 ml at a concentration of 2 mmol·L⁻¹. -1 A solution of MgSO4·7H2O and 50 ml of *Pyrrosia lingua* solution were used, and this temperature was maintained for 7 days to help the plant adapt to the initial high-temperature stress; during the 32℃ to 34℃ stage: a single application of 30 ml of a 3 mmol·L⁻¹ solution was given. -1A solution of MgSO4·7H2O and 60 ml of *Pyrrosia lingua* solution were used, and the temperature was maintained for 7 days to help plants enhance the synergistic effect between roots and fungi at higher temperatures; during the 34℃ to 35℃ stage: a single application of 40 ml of a 4 mmol·L⁻¹ solution was given. -1 The solution contained MgSO4·7H2O and 70 ml of *Pyrrosia lingua* culture, and the temperature was maintained for 7 days. Afterwards, a high-temperature stress treatment was applied.

[0071] The control group (CK, room temperature, without inoculation with Indian piriformis) was cultured at room temperature by watering.

[0072] The high-temperature stress control group (CKHS, high-temperature stress, no inoculation with Indian pyriformis) was irrigated with water, while the rest of the high-temperature stress treatment method was the same as that of the high-temperature inoculated Indian pyriformis and magnesium group (PIHS+Mg).

[0073] To facilitate the comparison between the rhododendrons obtained in this embodiment and the control group, the following measurement method was used in this embodiment:

[0074] 1.2.1 Determination of High Temperature Stress Indicators

[0075] The high-temperature stress process is as follows:

[0076] Plants were cultured in an artificial climate chamber at 35°C, ensuring 12 hours of light and 80% humidity daily. To avoid water stress caused by high-temperature treatment, a tray containing 1 cm of sterile water was placed at the bottom of the pots. Plants and soil were harvested after 5 days of high-temperature stress. Leaves from the 3rd to 8th leaf tip (facing downwards) were selected for physiological parameter determination, avoiding the collection of leaves that had turned brown. After collecting plant samples, soil samples were quartered, sieved through a 2 mm sieve, and used for soil chemical property determination. Root samples were frozen in liquid nitrogen and then stored at -80°C for root transcriptome and metabolome analysis.

[0077] 1.2.2 Determination of physiological and biochemical indicators of rhododendron

[0078] The soluble protein content (μg) in leaves and roots was measured. -1 The determination principle is the biuret method;

[0079] The soluble protein content was determined using a kit from Jiangsu Jingmei Co., Ltd. For specific methods, please refer to the kit instructions.

[0080] 1.2.3 Determination of Soil Physicochemical Properties

[0081] MDA content (nmol·g) -1 The malondialdehyde content of azaleas is determined using the thiobarbituric acid method.

[0082] H2O2 content (μmol·g) -1The principle of the determination is to measure the ability of titanium sulfate to form a yellow titanium peroxide complex at a wavelength of 415 nm.

[0083] The assay was performed using a kit from Beijing Solarbio Science & Technology Co., Ltd. Please refer to the kit instructions for specific methods.

[0084] 1.3 Results

[0085] Depend on Figure 1 It is known that after using the Indian piriformis liquid and magnesium irrigation method provided by the present invention, the overall height of the rhododendron is higher, the leaf area is larger, and the leaves are greener, which significantly alleviates the wilting and yellowing symptoms of rhododendron leaves under high temperature stress.

[0086] Depend on Figure 2 , Figure 3 It can be seen that, after using the method of the present invention, in terms of rhododendron biomass, rhododendrons under high temperature stress have better new shoot growth and larger stem diameter; the fresh weight, including the fresh weight of the above-ground and underground parts, is also greater.

[0087] Depend on Figure 4 It can be seen that after using the method of the present invention, the antioxidant capacity of rhododendron under high temperature stress is improved, and Indian piriformis has a protective effect under high temperature stress.

[0088] Depend on Figure 5 It is evident that by using this method, rhododendrons can maintain or reduce the content of soluble proteins, helping them maintain protein stability under adverse conditions.

[0089] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for improving heat tolerance of Rhododendron by synergistic effect of Magnaporthe grisea and magnesium, characterized in that, It comprises: The Indian pear-shaped fungus solid culture is applied to the soil around the rhododendron root, then the Indian pear-shaped fungus liquid culture is applied to the soil around the rhododendron root twice with an interval of 10 days and an amount of 50 ml, MgSO4·7H2O is applied to the soil around the rhododendron root twice with an interval of 5 days after a preset interval of days after the last application of the Indian pear-shaped fungus liquid culture, then the rhododendron is cultivated at an initial high temperature stress temperature, the high temperature stress temperature is gradually increased according to a preset condition until a target high temperature stress temperature is reached, MgSO4·7H2O and the Indian pear-shaped fungus liquid culture are applied according to a preset condition during the high temperature stress process, and finally the rhododendron with improved heat resistance is screened according to a preset condition.

2. The method for improving heat tolerance of Rhododendron by synergistic effect of Guignardia indica and magnesium as claimed in claim 1, wherein, The preparation method of the Indian pear-shaped fungus solid culture comprises: The culture solution was prepared to contain the following components at the final concentrations: 6.0 g L -1 Potato infusion, 20.0 g L -1 Glucose, 20.0 g L -1 Agar, 6.0 g L -1 Coconut water and 0.1 mg L -1 Indole acetic acid, IAA; The culture solution is sterilized at 121 DEG C for 20 minutes, and the pH thereof is adjusted to 5.5; The Pi fungus block with a diameter of 0.5 cm is cut using a 200 L pipette tip, and is placed in a culture medium plate containing the culture solution, and then is cultured at 28 DEG C in the dark for 14 days, until the mycelium grows to a diameter of 8 cm, to obtain the Indian pear-shaped fungus solid culture with mycelium and spore aggregates, i.e. the Indian pear-shaped fungus solid culture is obtained.

3. The method for improving the heat resistance of rhododendrons by utilizing the synergistic effect of *Pyrrosia lingua* and magnesium as described in claim 2, characterized in that... The preparation method of the Indian pear-shaped fungus liquid culture comprises: The culture solution was prepared to contain the following components at the final concentrations: 6.0 g·L -1 Potato infusion, 20.0 g·L -1 Glucose, 2.0 g·L -1 Corn steep liquor and 0.1 mg·L -1 Cell division factor CK; The culture solution is sterilized at 121 DEG C for 20 minutes, and the pH thereof is adjusted to 5.5; The fungus block of the Indian pear-shaped fungus solid culture with a diameter of 0.5 cm is cut, and is placed in a culture container containing the culture solution, and then is placed on a shaking table and cultured at 28 DEG C and 160 r / min in the dark for 15 days, to obtain the Indian pear-shaped fungus liquid culture.

4. The method for improving heat tolerance of Rhododendron by synergistic effect of Guignardia bidwellii and magnesium as claimed in claim 1, wherein the said method comprises of applying the said Guignardia bidwellii to the said Rhododendron plant. The soil around the roots of the azalea was applied with MgS04·7H20 twice, each time with a dosage of 20 ml and a concentration of 2 mmol·L -1 .

5. A method for improving the heat resistance of rhododendrons by utilizing the synergistic effect of *Pyrrosia lingua* and magnesium, as described in any one of claims 1 to 4, characterized in that... The initial high temperature stress temperature is 30 DEG C, and the target high temperature stress temperature is 35 DEG C.

6. The method for improving heat tolerance of Rhododendron by synergistic effect of Guignardia bidwellii and magnesium as claimed in claim 5 wherein, The method for subjecting the rhododendron to high temperature stress comprises: The rhododendron is cultivated at an initial high temperature stress temperature of 30 DEG C, and when it has no abnormal growth reaction, the high temperature stress temperature is gradually increased by 1-2 DEG C / week until the target high temperature stress temperature of 35 DEG C is reached.

7. The method for improving heat tolerance of Rhododendron by synergistic effect of Guignardia bidwellii and magnesium as claimed in claim 6 wherein, When the rhododendron has no abnormal growth when cultivated at the high temperature stress temperature, the high temperature stress temperature is adjusted in temperature steps of 30-32 DEG C, 32-34 DEG C and 34-35 DEG C; ​ When the high temperature stress temperature is adjusted each time, MgSO4·7H2O and the Indian pear-shaped fungus liquid culture are applied according to a standard amount in a preset temperature interval; The standard quantity of the temperature gradient interval of 30-32 is: 20 ml of 2 mmol / L MgSO4·7H2O, 50 ml of Pyricularia indica liquid bacterial solution; -1 The standard quantity of the temperature gradient interval of 30-32 is: 20 ml of 2 mmol / L MgSO4·7H2O, 50 ml of Pyricularia indica liquid bacterial solution; The standard quantity of the temperature gradient interval of 32-34 is: 30 ml of 3 mmol / L MgSO4·7H2O, 60 ml of Pyricularia grisea liquid bacterial solution; -1 The standard quantity of the temperature gradient interval of 32-34 is: 30 ml of 3 mmol / L MgSO4·7H2O, 60 ml of Pyricularia grisea liquid bacterial solution; The standard quantity for the temperature gradient interval of 34-35 is: 40 ml of a 4 mmol L -1 MgSO4.7H2O, 70 ml of a Pyricularia indica liquid bacterial solution.

8. The method for improving heat tolerance of Rhododendron by synergistic effect of Guignardia bidwellii and magnesium as claimed in claim 6 wherein, When the rhododendron has abnormal growth when cultivated at the high temperature stress temperature, the temperature is stopped from being increased, and the current temperature stage is extended to 10 days, and MgSO4·7H2O and the Indian pear-shaped fungus liquid culture are applied according to a standard amount in a corresponding temperature interval, and meanwhile, the recovery of the plant is observed; ​ When the rhododendron recovers to normal growth after 10 days, the temperature is continued to be increased to the next high temperature stress temperature; When the rhododendron does not recover to normal growth after 10 days, the current temperature is maintained without further increase.

9. A rhododendron heat-tolerant cultivation method, characterized by, The rhododendron is cultivated by the method of any one of claims 1-8.

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