A method for increasing the wax content of mango leaf epidermis

Abstract

The invention belongs to the field of mango cultivation, and specifically relates to a composition for increasing the wax content of mango leaf epidermis and its application. The invention uses melatonin (MT) and palmitic acid (PA) in combination, and after spraying mango leaves, the wax content on the surface of 'Tainong No. 1' mango leaves can be significantly increased, and the composition of mango leaf wax can also be affected, so as to affect the resistance of mango leaves to biological and non-biological stresses, and provide a reference for the synthetic regulation of mango leaf epidermal wax.

Description

Technical Field

[0001] The invention belongs to the field of mango cultivation, and particularly relates to a method for increasing the wax content of mango leaf epidermis. Background Art

[0002] The aerial epidermis of terrestrial plants is covered with a layer of hydrophobic wax, which is the first line of defense against adverse external environments. Plant epidermal wax plays an important role in preventing water loss, inhibiting pathogenic bacteria and extending the storage period. At present, there have been a lot of studies on the regulation of plant epidermal wax synthesis, in order to increase the content of plant epidermal wax components, thereby improving the resistance of plants to adverse external environments.

[0003] Mango is one of the famous tropical fruits, and it is seriously susceptible to diseases and insect pests during its growth. Therefore, increasing the wax content on the surface of mango plant leaves plays an important role in the prevention and control of mango diseases and insect pests, and is beneficial to improving the resistance of mango leaves to biological and abiotic stresses. Summary of the invention

[0004] The invention provides a composition for improving the epidermal wax content of mango leaves and application thereof. The epidermal wax content of mango leaves can be improved by spraying the composition consisting of palmitic acid and melatonin.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A composition for increasing the wax content of mango leaf epidermis comprises the following components: melatonin and palmitic acid; the molar concentration ratio of each component in the composition is melatonin: palmitic acid = 0-100: 150-200.

[0007] Furthermore, the molar concentration ratio of each component in the composition is melatonin:palmitic acid=100:200.

[0008] The method for preparing the composition for increasing the wax content of mango leaf epidermis comprises the following steps:

[0009] If the composition contains a melatonin solution, melatonin and palmitic acid are dissolved in anhydrous ethanol, and then water is added to prepare a melatonin solution and a palmitic acid solution respectively according to a molar concentration ratio. Before use, the melatonin solution and the palmitic acid solution are mixed evenly in equal volumes to obtain the solution; if the composition does not contain a melatonin solution, palmitic acid is dissolved in anhydrous ethanol, and then water is added to prepare a palmitic acid solution according to a molar concentration ratio to obtain the solution.

[0010] The above-mentioned composition for increasing the wax content in mango leaf epidermis is used for increasing the wax content in mango leaves.

[0011] The above-mentioned composition for increasing the wax content in mango leaf epidermis is used to increase the wax content in mango leaves and thus improve the resistance of mango leaves to mango anthracnose.

[0012] Application of the above-mentioned composition for increasing the wax content in mango leaf epidermis to regulating the wax composition of mango leaves.

[0013] Furthermore, the compound can increase the content of terpenes, esters, fatty acids, aldehydes and other compounds, and reduce the content of alkanes and alcohols; or, the compound can increase the content of terpenes and fatty acids, and reduce the content of alkanes, alcohols, aldehydes, esters and other compounds; or, the composition can increase the content of terpenes and reduce the content of alkanes, alcohols, aldehydes, fatty acids, esters and other compounds; or, the composition can increase the content of fatty acids and ester compounds, and reduce the content of alkanes, alcohols, aldehydes, terpenes and other compounds.

[0014] Furthermore, the mango variety is 'Tainong No. 1' mango.

[0015] A method for increasing the wax content of mango leaf epidermis and / or adjusting the wax composition of mango leaves comprises the following steps:

[0016] (1) preparing a melatonin solution and a palmitic acid solution according to the molar concentration ratio of the composition of claim 1 or 2, wherein the molar concentration of melatonin is 0-100 μM and the molar concentration of palmitic acid is 150-200 μM;

[0017] (2) If the composition contains melatonin, mix equal volumes of melatonin solution and palmitic acid solution and spray the mixture on mango leaves; if the composition does not contain melatonin, spray the palmitic acid solution on mango leaves.

[0018] Furthermore, the composition is sprayed at the following time: when the mango shoots have finished sprouting and entered the tender leaf stage; spraying on the upper and lower epidermis of the yellow-to-green leaves of the newly sprouted shoots; if it is a mango seedling, spraying 50 mL of the composition per plant; if it is an adult mango tree, according to the number of sprouted branches, the amount of the composition used per branch does not exceed 50 mL; spraying once every 2 days, for a total of 3 times.

[0019] Beneficial effects of the present invention:

[0020] The present invention uses melatonin (MT) and palmitic acid (PA) in combination. After spraying mango leaves, the wax content on the surface of the 'Tainong No. 1' mango leaves can be significantly increased, and the composition of the mango leaf wax can also be affected. The content of terpenes, fatty acids and ester compounds in the wax is significantly increased. Therefore, the composition of the present invention affects the wax content and wax composition of the mango epidermis, thereby affecting the mango leaves' resistance to biological and non-biological stresses, and can improve the resistance of mango leaves to mango anthracnose, and also provide a reference for the synthetic regulation of mango leaf epidermis wax. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 The effects of different treatments on the wax content of mango leaves: MT: 100 μM MT; PA-1: 150 μM PA; PA-2: 200 μM PA; MT+PA-1: 100 μM MT+150 μM PA; MT+PA-2: 100 μM MT+200 μM PA. The experimental results are based on the average of three biological replicates. Different lowercase letters in the figure indicate significant differences at the 5% level.

[0023] Figure 2 The effect of different treatments on the proportion of wax components in the leaf epidermis of 'Tainong No. 1' mango. From bottom to top in the bar graph, they are alkanes, alcohols, aldehydes, fatty acids, esters, terpenes and others.

[0024] Figure 3 The carbon chain length distribution of alkane compounds after different treatments.

[0025] Figure 4 This is the carbon chain length distribution of alcohol compounds after different treatments.

[0026] Figure 5 This is the carbon chain length distribution of aldehyde compounds after different treatments.

[0027] Figure 6 This is the carbon chain length distribution of fatty acid compounds after different treatments.

[0028] in, Figure 3-6 In each group of bar graphs, the samples from left to right are: CK, MT, PA-1, PA-2, MT+PA-1, MT+PA-2.

[0029] Figure 7 This is the principal component analysis diagram of the wax components of mango leaf epidermis after different treatments.

[0030] Figure 8 The disease condition of leaves 6 days after inoculation with anthracnose. Note: The leaves on the left are the control group, and the leaves on the right are the 100μM MT+200μM PA treatment group. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] A composition for increasing the wax content of mango leaf epidermis comprises the following components: melatonin (MT) and palmitic acid (PA); the molar concentration ratio of each component is melatonin:palmitic acid=100:150.

[0034] The preparation method of the above composition comprises the following steps:

[0035] (1) Melatonin and palmitic acid were dissolved in anhydrous ethanol, and then water was added according to the molar concentration ratio to prepare melatonin solution and palmitic acid solution respectively; during the preparation process, a small amount of anhydrous ethanol was used to dissolve melatonin and palmitic acid respectively, and then an appropriate amount of OP-10 emulsifier (Shanghai McLean Biochemical Technology Co., Ltd., Lot#: C12199604, CAS: NONE98) was added to assist dissolution, and after mixing evenly, water was added according to the molar concentration ratio to prepare melatonin solution and palmitic acid solution respectively. For every 1L of exogenous reagent, about 1mL of anhydrous ethanol was used, and about 20μL of emulsifier was added.

[0036] (2) Before use, mix equal volumes of melatonin solution and palmitic acid solution.

[0037] Example 2

[0038] A composition for increasing the wax content of mango leaf epidermis comprises the following components: melatonin and palmitic acid; the molar concentration ratio of each component in the composition is melatonin:palmitic acid=100:200; the volume ratio of each component in the composition is melatonin:palmitic acid=1:1.

[0039] The preparation method of the above composition comprises the following steps:

[0040] The preparation method is the same as that in Example 1.

[0041] Example 3

[0042] A composition for increasing the wax content of mango leaf epidermis comprises the following components: palmitic acid.

[0043] The preparation method thereof comprises the following steps:

[0044] Dissolve palmitic acid in anhydrous ethanol, add water after adding an emulsifier, and prepare a palmitic acid solution according to the molar concentration. Add about 20 μL of emulsifier to every 1 mL of anhydrous ethanol, and the molar concentration of palmitic acid is 150-200 μM. The amount of anhydrous ethanol and emulsifier used is referenced to Example 1.

[0045] The above-mentioned composition is sprayed on the leaves of 'Tainong No. 1' mango, which can increase the wax content of the mango leaves and change the wax composition of the mango leaves. For example, the compound can increase the content of terpenes, esters, fatty acids, aldehydes and other compounds, and reduce the content of alkanes and alcohols (150PA). Alternatively, the compound can increase the content of terpenes and fatty acids, and reduce the content of alkanes, alcohols, aldehydes, esters and other compounds (200PA). Alternatively, the composition can increase the content of terpenes and reduce the content of alkanes, alcohols, aldehydes, fatty acids, esters and other compounds (100μM MT+150μMPA). Alternatively, the composition can increase the content of fatty acids and ester compounds, and reduce the content of alkanes, alcohols, aldehydes, terpenes and other compounds (100μM MT+200μM PA).

[0046] Example 4

[0047] A method for increasing the wax content of mango leaf epidermis comprises the following steps:

[0048] (1) When the shoots of the mangoes of 'Tainong No. 1' have finished sprouting and entered the tender leaf stage, prepare melatonin solution and palmitic acid solution respectively according to the method of Example 1, wherein the molar concentration of the melatonin solution is 100 μM and the molar concentration of the palmitic acid solution is 200 μM; (2) Take 25 ml of each of the melatonin solution and palmitic acid solution, mix them evenly, and spray them on the front and back of the mango leaves. Spray once every 2 days, and spray them 3 times in total.

[0049] Example 5

[0050] A method for increasing the wax content of mango leaf epidermis comprises the following steps:

[0051] (1) After the 'Tainong No. 1' mango has finished sprouting and entered the tender leaf stage, a melatonin solution and a palmitic acid solution are prepared according to the method of Example 1, wherein the molar concentration of the melatonin solution is 100 μM, and the molar concentration of the palmitic acid solution is 150 μM;

[0052] (2) Take 25 ml of melatonin solution and 25 ml of palmitic acid solution respectively, mix them evenly, and spray them on the front and back of mango leaves. Spray once every 2 days, and spray 3 times in total.

[0053] Example 6

[0054] A method for increasing the wax content of mango leaf epidermis comprises the following steps:

[0055] (1) When the 'Tainong No. 1' mango has finished sprouting and entered the tender leaf stage, a palmitic acid solution is prepared according to the method of Example 1, and the molar concentration of the palmitic acid solution is 150 μM;

[0056] (2) Take 50 ml of palmitic acid solution and spray it on the front and back of mango leaves. Spray once every 2 days for a total of 3 times.

[0057] Example 7

[0058] A method for regulating the wax composition of mango leaves comprises the following steps:

[0059] (1) When the 'Tainong No. 1' mango has finished sprouting and entered the tender leaf stage, a palmitic acid solution is prepared according to the method of Example 1, and the molar concentration of the palmitic acid solution is 200 μM;

[0060] (2) Spray 50 ml of palmitic acid solution on the front and back of mango leaves once every 2 days for a total of 3 times.

[0061] Example 8

[0062] A method for regulating the wax composition of mango leaves comprises the following steps:

[0063] (1) After the 'Tainong No. 1' mango has finished sprouting and entered the tender leaf stage, a melatonin solution and a palmitic acid solution are prepared according to the method of Example 1, wherein the molar concentration of the melatonin solution is 100 μM, and the molar concentration of the palmitic acid solution is 200 μM;

[0064] (2) Take 25 ml of melatonin solution and palmitic acid solution respectively, mix them evenly, and spray them on the front and back of mango leaves. Spray once every 2 days, and spray 3 times in total.

[0065] Example 9

[0066] A method for increasing the wax content of mango leaf epidermis comprises the following steps:

[0067] (1) After the 'Tainong No. 1' mango has finished sprouting and entered the tender leaf stage, a melatonin solution and a palmitic acid solution are prepared according to the method of Example 1, wherein the molar concentration of the melatonin solution is 100 μM, and the molar concentration of the palmitic acid solution is 150 μM;

[0068] (2) Take 25 ml of melatonin solution and palmitic acid solution respectively, mix them evenly, and spray them on the front and back of mango leaves. Spray once every 2 days, and spray 3 times in total. Effects of different exogenous agents on mango leaf wax

[0069] 1 Materials and methods

[0070] 1.1 Test materials

[0071] The experimental material selected for the study is the mango variety 'Tainong No. 1', which is mainly grown in Sanya City, Hainan Province. One-year-old seedlings planted in the experimental base were selected, and the mango seedlings were subject to unified routine management measures to ensure the consistency of growth conditions. When the mango seedlings finished sprouting and entered the tender leaf stage, the subsequent treatment test of the leaves began.

[0072] 1.2 Treatment of mango leaves with exogenous reagents

[0073] Melatonin and palmitic acid were weighed according to the dosage of the formula, and equal volumes of 100μM melatonin solution and 150μM and 200μM palmitic acid solutions were prepared respectively. In order to facilitate the comparison of experimental effects, during the preparation process, 1mL of anhydrous ethanol and 20μL of emulsifier were added for every 1L of exogenous reagent when preparing each concentration of exogenous reagent. An equal amount of anhydrous ethanol and OP-10 emulsifier were added to clean water as the control group (CK).

[0074] Mango leaves with consistent growth, no pests or other mechanical damage were selected. 100μM melatonin (MT) and 150μM and 200μM palmitic acid (PA) were sprayed evenly on the front and back of the mango leaves with 50ml each; 100μM MT+150μM PA (MT+PA-1) were sprayed with 25ml each after mixing evenly; 100μM MT+200μM PA (MT+PA-2) were sprayed with 25ml each after mixing evenly. The mango leaves in the control group were sprayed with 50ml of water with equal amounts of anhydrous ethanol and OP-10 emulsifier added. Three mango seedlings were treated in each treatment, and three replicates were set for each treatment. The spraying was performed once every 2 days, for a total of 3 sprayings. On the 7th day of exogenous agent treatment, 3 leaves from the same part of each plant were taken for subsequent wax content and component analysis.

[0075] 1.3 Determination of wax content in mango leaf epidermis

[0076] The chloroform dissolution method was used to extract the epidermal wax of mango leaves. The amount of chloroform was adjusted appropriately according to the characteristics of the leaves, so as to completely immerse the leaves. The surface area of ​​mango leaves was measured using a leaf area meter (CI-203). The leaves to be tested were slowly rinsed with tap water and placed in a cool place to dry. In a fume hood, 80 ml of chloroform was fully soaked for 1 min, and the leaves were gently turned over with a glass rod during this period. 20 ml of the filtrate after soaking was transferred to a brown sample bottle that had been weighed in advance, and 2 μL of n-tetracosane solution (10 mg / mL) was added as an internal standard. The solution was blown dry by a nitrogen blower, and the weight of the brown sample bottle after drying was weighed. The difference between the two weighings is the weight of the epidermal wax of mango leaves in the filtrate taken.

[0077] Wax content (μg / cm 2 ) = wax weight / leaf area

[0078] 1.4 Derivatization reaction and component analysis of mango leaf epidermal wax

[0079] Take 1 mg of waxy crude extract, add 200 μl pyridine and 200 μl N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), place in a 70°C oven for 1 hour, blow dry all the liquid in the bottle with nitrogen again, add 1 ml of chromatographic grade chloroform. Use a 1 ml sterile syringe to pass the solution through a 0.45 μm organic filter membrane, filter into a 2 mL brown injection bottle, tighten the bottle cap and seal it with plastic wrap, and place in a -80°C refrigerator to wait for the machine to measure the sample.

[0080] The chemical composition of mango leaf cuticle wax was analyzed by gas chromatography-mass spectrometry (GC-MS, Bruker 450-GC, Bruker 320-MS) and chromatographic column (BR-5MS, 30×0.25×0.25). Helium at 1.2 mL / min was used as carrier gas. The instrument parameters were as follows: the injection port and transfer line temperature were both set to 280°C; ion source temperature, 250°C, quadrupole temperature, 150°C; electron energy (EI), 70 eV; scanning range was 50-650 m / z. After the sample was injected into the GC-MS, the instrument was operated at 50°C for 2 min, followed by 200°C at a rate of 40°C / min for 2 min. Finally, the temperature was increased from 200°C to 320°C at a rate of 3°C / min and maintained for 30 min.

[0081] 1.5 Analysis of disease resistance of mango leaves under different treatments

[0082] 1.5.1 Test pathogens

[0083] The pathogen of mango anthracnose, Colletotrichum gloeosporioides, was isolated, identified and preserved by the Horticultural Products Preservation and Processing Laboratory of the South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences and is numbered W1.

[0084] 1.5.2 Experimental design and treatment methods

[0085] Twenty-five mango leaves were collected from the mango leaves treated with 100 μM MT+200 μM PA (Group 1) and the mango leaves from the control group (Group 2), and the mango leaves were rinsed with a slow stream of clean water and then dried for later use.

[0086] 1.5.3 Vaccination method and disease statistics

[0087] The non-injury inoculation method of bacterial cakes was used. Five treatment points were inoculated on both sides of each leaf vein, including four inoculation points (bacterial cakes after 6 days of PDA culture) and one control point (sterile cake of PDA culture medium). Sterile cotton balls were used to keep the moisture and cultured in a sterile inoculation box at room temperature of 26-28℃. On the 6th day after the non-injury inoculation, the incidence and disease index of mango anthracnose were counted, and the disease condition of the leaves was observed and photographed for record. The disease index algorithm is:

[0088]

[0089] DI = disease index, N = disease grade, M = number of corresponding disease grades, i = each grade of disease grade, S = total number of surveys. The disease grade of mango leaves refers to Diao Xingwang's method and is graded according to the diameter of lesions on detached leaves: Grade 0: no lesions; Grade 1: 0 < lesion diameter ≤ 3mm; Grade 3: 3mm < lesion diameter ≤ 6mm; Grade 5: 6mm < lesion diameter ≤ 9mm; Grade 7: 9mm < lesion diameter ≤ 12mm; Grade 9: 12mm < lesion diameter.

[0090] 1.5 Data Analysis

[0091] GraphPad prism 9 and Origin 2021 software were used to make bar graphs, Origin 2021 software was used for principal component analysis, and SPSS V23.0 software was used for significant difference analysis. The lowercase letters after any data indicate significant differences with p < 0.05. Three biological replicates were performed for each treatment, and the data are expressed as mean ± SD.

[0092] 2 Results and analysis

[0093] 2.1 Effects of exogenous reagents on wax content in mango leaf epidermis

[0094] The effects of spraying different exogenous agents on the epidermal wax content of mango leaves of different varieties were different ( Figure 1 and Table 1).

[0095] Increase multiple = treatment group content / control group content

[0096] Table 1 Changes in wax content in mango leaf epidermis under different treatments

[0097] deal with <![CDATA[Wax content (μg / cm 2 )]]> Increase multiple CK 11.76±1.48e / MT 14.09±0.90de 1.20 PA-1 24.06±2.54b 2.05 PA-2 18.43±1.03c 1.57 MT+PA-1 15.77±2.28cd 1.34 MT+PA-2 37.66±1.48a 3.20

[0098] The wax content of mango leaf epidermis in the control group'Tainong No. 1' was 11.76 μg / cm 2 After treatment with 100 μM MT solution, the wax content of the epidermal wax of mango leaves of ‘Tainong No. 1’ increased significantly to 14.09 μg / cm 2 , which is more than 1 times that of the control group, but compared with the control group, the effect of increasing the wax content in the leaf epidermis was not significant.

[0099] Compared with the control group, the wax content of the leaves treated with 150μM PA solution increased significantly, reaching more than 2 times that of the control group. After treatment with 200μM PA, the wax content of the leaves reached more than 1 times that of the control group. Compared with the control group, the wax content of the leaves treated with 100μM MT+150μM PA mixed solution reached more than 1 times that of the control group. Compared with the control group, the wax content of the leaves of 'Tainong No. 1' mango increased significantly after treatment with 100μM MT+200μM PA mixed solution, reaching more than 3 times that of the control group, with the most significant increase.

[0100] Therefore, there are significant differences in the effects of different treatment methods on the epidermal wax content of mango leaves of 'Tainong No. 1'. The wax content of the five treatment groups increased to varying degrees. Among them, the wax content increased in the 150μM PA treatment, as well as the 200μM PA and 100μMMT+150μM PA treatments. The treatment with 100μM MT+200μM PA had the most significant improvement, with the wax content reaching more than 3 times that of the control group, significantly higher than the other treatment groups. This shows that the treatment with 150μM PA, 200μM PA, 100μM MT+150μM PA and 100μM MT+200μM PA reagents can significantly increase the epidermal wax content of 'Tainong No. 1' leaves.

[0101] 2.2 Effects of exogenous agents on wax components of mango leaf epidermis

[0102] To further study the effects of different treatments on the wax components of mango leaf cuticle, the wax components of mango leaf cuticle after treatment were identified. The results of GC-MS analysis showed that the wax components of mango leaf cuticle of 'Tainong No. 1' were mainly composed of alkanes, alcohols, aldehydes, fatty acids, esters, terpenes and other unclassified compounds ( Figure 2According to the content of each component and the epidermal wax content, the content of each wax component and the improvement rate are calculated respectively.

[0103] Content of each component (μg / cm 2 ) = leaf wax content * proportion of this component

[0104] Increase multiple = treatment group content / control group content

[0105] Table 2 Effects of different treatments on the content of wax components in mango leaf epidermis (μg / cm 2 )

[0106] deal with Alkanes Alcohols Aldehydes fatty acid Esters Terpenes other CK 2.49±0.46a 1.52±0.16a 2.41±0.75ab 0.18±0.02cd 2.77±0.72b 2.14±0.53d 0.23±0.01ab MT 1.95±0.55ab 1.48±0.41a 2.90±0.52a 0.22±0.02bc 2.77±0.60b 4.48±0.51c 0.30±0.14a PA-1 1.74±0.54bc 1.21±0.57a 3.06±0.43a 0.24±0.05ab 3.12±0.57b 14.40±1.84a 0.29±0.07ab PA-2 1.70±0.11bc 0.91±0.28ab 1.80±0.17bc 0.29±0.02a 1.66±0.76b 11.81±0.56b 0.26±0.03ab MT+PA-1 1.02±0.31cd 0.54±0.17b 1.17±0.39c 0.16±0.02d 1.76±0.58b 10.98±1.12b 0.14±0.11b MT+PA-2 0.88±0.01d 0.91±0.16ab 1.30±0.18c 0.19±0.01cd 33.09±1.13a 1.13±0.02d 0.15±0.02ab

[0107] Compared with the clear water control (CK), different treatments had a greater impact on the composition of the epidermal wax of the mango leaves of 'Tainong No. 1' (Table 2), and the content of each component also showed great differences. After treatment with 150μM PA, the content of terpenoids reached more than 6 times that of the control group, and after treatment with 200μM PA, the content of terpenoids reached more than 5 times that of the control group. After treatment with 100μM MT+150μM PA, the content of terpenoids reached more than 5 times that of the control group, and the content increased significantly. After treatment with 100μM MT+200μM PA, the content of ester compounds reached more than 11 times that of the control group, and the content increased significantly.

[0108] The above results show that different treatment methods have a significant impact on the component content of wax.

[0109] 2.2.1 Aliphatic compounds

[0110] The aliphatic compounds detected in the epidermal wax of mango leaves mainly include alkanes, alcohols, aldehydes and fatty acids. Alkanes are the main components of aliphatic compounds. The carbon chain length of ultra-long chain alkanes in mango leaves is between C16-C34 ( Figure 3 ). Among them, C25 and C26 alkanes were the main alkane compounds in the leaf wax of 'Tainong No. 1' after the five treatments. In the leaf wax of 'Tainong No. 1' mango, octadecane was detected in all treatments except 150μM PA, hexacosane was only found in CK and 150μM PA treatments, and nonacosane was only present in CK.

[0111] Alcohols are one of the aliphatic compounds in the wax of mango leaf epidermis. Figure 4 , No nonadecanol was found in all treatments of 'Tainong No. 1'. Heneicosanol, tetracosanol and heptacosanol were detected in all treatments. In the mango leaves of 'Tainong No. 1', the content of tetracosanoid increased significantly after treatment with 100μM MT, and the content of heptacosanoid decreased significantly after treatment with 100μM MT+150μM PA.

[0112] Aldehydes are one of the main components of aliphatic compounds. Figure 5 The carbon chain length of aldehydes is mainly C24-C32. They are tetracosanal, hexacosanal, octacosanal, nonacosanal and dotriacontanal. In the leaves of mangoes of 'Tainong No. 1', dotriacontanal was not detected in the two mixed solution treatments, but was detected in all other treatments.

[0113] Fatty acids account for a relatively low proportion in the wax of mango leaf epidermis. Figure 6 The carbon chain length of fatty acids was mainly C16 and C18. Hexadecanoic acid and octadecanoic acid were detected in the leaves of 'Tainong No. 1' in all treatments, and the hexadecanoic acid content increased significantly after 150μM PA and 200μM PA treatments compared with the control group.

[0114] 2.2.2 Terpenoids

[0115] In addition to aliphatic compounds, terpenoids are also the main components of mango leaf epidermal wax (Table 3). After treatment in each group, the terpenoids detected in mango leaves mainly included γ-tocopherol, DL-α-tocopherol, squalene, β-amyrin, β-amyrin, α-amyrin and cork ketone. Among them, γ-tocopherol can be found in all treatments, and DL-α-tocopherol is only detected in the CK treatment of 'Tainong No. 1' mango leaves. Squalene has a low content among terpenoids, and squalene can be detected in all treatments. β-amyrin is the main substance in terpenoids. After 100μM MT and 150μM PA treatments were performed on 'Tainong No. 1' mango leaves, the contents of squalene, β-amyrin and α-amyrin increased significantly. After 150μM PA and 200μM PA treatments were performed on 'Tainong No. 1' mango leaves, the content of β-amyrin increased significantly. Cork ketone was not detected.

[0116] Table 3 Contents of main terpenoid compounds after different treatments (μg / cm2)

[0117]

[0118] 2.2.3 Esters and other unclassified compounds

[0119] In addition to aliphatic and terpenoid compounds, esters and a small amount of other unclassified substances were also detected in the wax of mango leaf epidermis. The esters in the wax of mango leaf epidermis were mainly C16 and C24.

[0120] In addition, the unclassified other compounds were mainly phenolic compounds, which were detected in all treatments. The phenolic compounds were mainly C14 and C23 phenols, which had no significant changes in the leaves among the treatments.

[0121] 2.2.4 Principal component analysis of wax components

[0122] The wax compounds (alkanes, alcohols, aldehydes, fatty acids, terpenes, esters and other compounds) detected in the mango leaf cuticle after treatment with different exogenous reagents and clean water were subjected to PCA analysis ( Figure 7 ). PC1 and PC2 of 'Tainong No. 1' were 44.1% and 24.8%, respectively, which could explain 68.9% of the variation. After treatment with different exogenous reagents, the samples were clustered, indicating that the different exogenous reagents used played a specific regulatory role in the composition and content of wax in mango leaf epidermis.

[0123] 2.3 Analysis of leaf disease resistance

[0124] like Figure 8 As shown, the incidence of mango leaves in Group 1 was 8% on the 6th day after inoculation with anthracnose, and the disease index was 4; no disease was observed on the 6th day after inoculation with anthracnose on mango leaves in Group 2. No disease was observed in all treatment control points.

[0125] Therefore, the wax content of mango leaves sprayed with the combination of 100 μM MT + 200 μM PA increased, and the resistance to mango anthracnose was enhanced.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composition for increasing the wax content of mango leaf epidermis, characterized in that: The composition comprises the following components: melatonin and palmitic acid; the molar concentration ratio of the components in the composition is melatonin: palmitic acid = 100:

200.

2. A method for preparing a composition for increasing the wax content of mango leaf epidermis as claimed in claim 1, characterized in that: The following steps are involved: Melatonin and palmitic acid are dissolved in anhydrous ethanol, and then water is added to prepare melatonin solution and palmitic acid solution respectively according to the molar concentration ratio. Before use, equal volumes of melatonin solution and palmitic acid solution are mixed evenly.

3. Use of a composition for increasing the wax content of mango leaf epidermis as claimed in claim 1 in increasing the wax content of mango leaves.

4. Use of the composition for increasing the wax content in mango leaf epidermis as claimed in claim 1 in increasing the wax content in mango leaves and thus increasing the resistance of mango leaves to mango anthracnose.

5. Use of a composition for increasing the wax content of mango leaf epidermis as claimed in claim 1 in regulating the wax composition of mango leaves.

6. The use according to claim 5, characterized in that: The composition can increase the content of ester compounds in mango leaf wax and reduce the contents of alkanes, alcohols, aldehydes, terpenes and other compounds.

7. The use according to any one of claims 4 to 6, characterized in that: The mango variety is 'Tainong No. 1' mango.

8. A method for increasing the wax content of mango leaf epidermis and / or adjusting the wax composition of mango leaves, characterized in that: The following steps are involved: (1) According to the molar concentration ratio of the composition of claim 1, a melatonin solution and a palmitic acid solution are prepared respectively, wherein the molar concentration of melatonin is 100 μM and the molar concentration of palmitic acid is 200 μM; (2) Mix equal volumes of melatonin solution and palmitic acid solution and spray them on mango leaves.

9. The method according to claim 8, characterized in that The composition is sprayed on the upper and lower epidermis of the yellow-to-green leaves of the newly sprouted mangoes after the mangoes have finished sprouting and entered the tender leaf stage; if it is a mango seedling, 50 mL of the composition is sprayed on each mango seedling; if it is an adult mango tree, the dosage of the composition is no more than 50 mL per branch according to the number of sprouted branches; spraying is performed once every 2 days, and a total of 3 sprayings are performed.

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