Method for regulating and controlling aroma of grape fruits through exogenous plant growth regulator

Abstract

The invention provides a method for regulating and controlling aroma of grape fruits through an exogenous plant growth regulator, which comprises the following steps of: spraying three exogenous plant hormones, namely methyl jasmonate, phenylalanine and strigolactones, on 'Hanxiangmi' grape fruits with strong rose aroma, and analyzing the aroma composition and content of the treated grape fruits. The result shows that the rose fragrance intensity of the'Hanxiangmi 'grapes is enhanced after the jasmonic acid methyl ester treatment; after strigolactones treatment, components such as alpha-terpilenol, beta-ionone, nonanoic acid, geraniol and the like in grape fruits are prominent, so that the treated grapes are converted into mixed fragrance type grapes with flower fragrance, fruit fragrance and grass fragrance, and the fragrance layers are rich; and the treatment effect of phenylalanine is not obvious. The invention provides a reference for the research of strigolactone in fruit quality.

Description

Technical Field

[0001] This invention belongs to the field of fruit cultivation technology, specifically relating to a method for regulating the aroma of grape fruits using exogenous plant growth regulators. Background Technology

[0002] Grapes (Vitis vinifera L.) are one of the most widely cultivated fruit trees in the world with significant economic value. my country's grape industry has developed rapidly, and to meet consumer demand for high-quality fruit, scientific cultivation and management measures are needed to improve the overall quality of grape berries. Grape aroma, as a crucial component of flavor quality, significantly influences consumer sensory experience and market acceptance. Different grape varieties exhibit unique flavor characteristics, and a pleasant aroma not only enhances edible value but also produces positive physiological and psychological effects on humans. Grape aroma is a complex system composed of various volatile organic compounds (VOCs), whose types, proportions, and concentrations collectively determine the overall aroma characteristics of the fruit. Based on different chemical functional groups, volatile substances can be classified into acids, alcohols, aldehydes, esters, ketones, and terpenes. Among them, terpenes, aldehydes, and esters typically impart floral and fruity aromas to the fruit; alcohols often exhibit grassy notes; while acids often carry unpleasant odors.

[0003] From a metabolic perspective, grape aroma compounds mainly originate from three biosynthetic pathways: fatty acid metabolism, amino acid metabolism, and terpene synthesis. Linear-chain aldehydes, alcohols, ketones, and esters are primarily formed through fatty acid metabolism; branched-chain aldehydes, ketones, alcohols, and esters mainly originate from amino acid metabolism, particularly using branched-chain amino acids as precursors; and terpenes, as the most representative aroma components in grapes, have been identified with over 50 terpene compounds that contribute to sensory perception. Their content directly determines the intensity and type of aroma and is easily regulated by various agronomic practices. Based on the metabolic characteristics and sensory performance of aroma compounds, grape flavors are often categorized into types such as rose, strawberry, grassy, ​​and aromatic.

[0004] 'Hanxiangmi' grapes are an extremely early-maturing seedless grape variety, a triploid hybrid of European and American grapes. They are highly favored by consumers for their rich rose aroma and are now widely cultivated in Central and Southern my country. In grape cultivation, to improve yield and fruit quality, growers often use exogenous plant growth regulators for intervention and regulation. Methyljasmonate (MeJA), as an endogenous plant hormone belonging to the jasmonic acid (JA) family, can broadly regulate plant growth and development, stress response, and the accumulation of secondary metabolites, thereby affecting fruit aroma formation. It has been proven to promote the accumulation of flavor-related substances such as flavonoids, total phenols, and anthocyanins. Phenylalanine (Phe) is the starting substrate for phenylpropane metabolism and can participate in the synthesis of aroma substances through the benzyl phenylpropane (BPV) branch pathway, in conjunction with terpenes and fatty acid derivatives. strigolactones (SL) are a new type of plant hormone that mainly acts on plant branching regulation and stress relief. However, there are no reports on their role in regulating fruit aroma quality. Summary of the Invention

[0005] To address the problems existing in current technologies, this invention provides a method for regulating grape aroma through exogenous plant growth regulators. Using the 'Hanxiangmi' grape variety, known for its rich rose aroma, as the experimental material, different types of exogenous plant growth regulators (including methyl jasmonate, phenylalanine, and strigolactone) were sprayed in the field. Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was then used for qualitative and quantitative analysis of volatile aroma compounds in mature grapes, exploring the effects of different hormone treatments on the composition and content of grape aroma. This study aims to reveal the regulatory mechanism of plant hormones on grape aroma metabolism, providing a theoretical basis and technical support for improving the aroma quality of grapes.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention has discovered that three exogenous plant growth regulators—methyl jasmonate (MeJA), phenylalanine (Phe), and strigolactones (SL)—can regulate the synthesis of aroma compounds in grape fruits, thereby affecting the types and content of grape aromas and altering their aroma characteristics. This invention employs headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) to analyze 'Hanxiangmi' grape fruit samples at maturity after treatment with three different exogenous plant growth regulators. The volatile organic compounds in each group were identified and quantified. Further analysis of the measured aroma compounds was conducted to screen for differential aroma substances. OAV values ​​were used to further screen for the major aroma compounds with high contribution rates among the differential aroma substances, thus determining the main causes and mechanisms leading to differences in grape fruit aroma after exogenous plant growth regulator application.

[0008] On the one hand, the present invention provides a reagent for regulating the aroma of grapes, including any one or more exogenous plant growth regulators selected from methyl jasmonate, phenylalanine, and strigolactone.

[0009] Methyl jasmonate and phenylalanine are the main volatile organic compounds synthesized in the plant aroma synthesis pathway. Using these two plant hormones as exogenous plant growth regulators to regulate plant aroma is a common method, but there is little research on using them to regulate the aroma of grapes. Strigolactones are a class of sesquiterpenoid plant hormones derived from carotenoids, with the molecular formula C1... 17 H 14 O5, with a chemical structure containing an enol ether bridge and a 5-hydroxyfuranone group (D ring), primarily functions to inhibit plant branching; act as a root secretion signal to stimulate the germination of seeds of parasitic weeds such as *Striga asiatica* and *Orobanche*; and stimulate hyphal branching of arbuscular mycorrhizal fungi, enhancing plant absorption of minerals such as phosphates. However, there is currently no research on the use of strigolactones as exogenous plant growth regulators to modulate plant aroma. To alter the aroma of grapes, optimize their flavor quality, and enrich their aroma characteristics, this invention treated grapes with methyl jasmonate, phenylalanine, and strigolactones. The results showed that the content of volatile organic compounds such as acids, esters, alcohols, and terpenes in grapes treated with these three plant growth regulators significantly increased, with the changes in acids, esters, and terpenes being the most pronounced. Among them, the grapes treated with methyl jasmonate had the highest content of nerol, n-hexanol, and geraniol; the grapes treated with phenylalanine had the highest content of substances such as ethyl heptanate, 3-hydroxy-2-butanone, and eucalyptol; and the grapes treated with strigolactones had the highest content of substances such as hexyl acetate and β-ionone.

[0010] Changes in the types and amounts of aroma compounds in grapes not only alter their aroma characteristics and fruit flavor profile, but certain volatile compounds can also enhance stress resistance and extend shelf life. For example, increased hexyl acetate content imparts fresh fruit aromas like strawberry and apple to table grapes, improving palatability; β-ionone, a carotenoid derivative, contributes violet and woody notes, enhancing the complexity of grape aromas; its antioxidant properties also protect the stability of other volatile components; terpenes and esters can inhibit fungal spore germination and delay ethylene release, thereby improving grape stress resistance and extending post-harvest shelf life. According to the research results of this invention, methyl jasmonate can be sprayed on grape berries to improve their stress resistance, post-harvest preservation period, and aroma. Treatment of grape berries with strigolactone can not only enhance the floral and fruity aroma of grape berries and enrich the aroma layers of grapes, thereby improving the quality and flavor of table grapes, but also synergistically strengthen the stress resistance and nutritional quality of grape berries through the presence of multiple prominent aroma components such as β-ionone, nonanoic acid, and caprylic acid.

[0011] Furthermore, the exogenous plant growth regulator is strigolactone.

[0012] Furthermore, the concentration of the strigolactone is 0.5-4 μmol / L.

[0013] On the other hand, the present invention provides a method for regulating the aroma of grapes by treating grapes with the reagents described in any of the preceding claims.

[0014] Since the content of aroma components cannot be used as a sufficient basis for determining the aroma characteristics of grapes, in order to clarify the contribution of key aroma compounds in grapes treated with three exogenous plant growth regulators to the overall aroma of the fruit, this invention also studied the OAV values ​​of differential aroma components under different treatments in some embodiments. The results showed that in the strigolactone treatment group, the main components included decanal, ethyl heptanoate, β-ionone, α-terpineol, nonanoic acid, and geraniol, which made the floral and sweet aromas of the treated grapes more prominent. After methyl jasmonic acid treatment, the prominent substances included n-hexanol, α-terpineol, geraniol, β-damascene, nonanoic acid, and caprylic acid, making the grapes more rose-like, fruity, and sweet. Under phenylalanine treatment, the OAV values ​​of n-hexanol, citronellol, and decanal in the fruit were particularly prominent, making the treated grapes more floral, rose-like, and grassy.

[0015] Among them, α-terpineol and geraniol are synthesized in the biosynthetic pathway of monoterpenes, using geraniol pyrophosphate (GPP), a product of the upstream terpenoid skeletal synthesis pathway, as a substrate. β-damascone is unique; it also occurs through the enzymatic conversion of GPP into farnesol, which further undergoes a series of enzymatic reactions in the carotenoid synthesis pathway, where it is converted into neoxanthin by carotenoid cleavage dioxygenases. This neoxanthin then forms β-damascone after a series of enzymatic reactions. This substance has an extremely low threshold and a high OAV value, exhibiting a strong aroma profile and contributing significantly to fruit aroma. Additionally, nonanoic acid, caprylic acid, and ethyl heptanoate are formed into medium-chain fatty acids through fatty acid synthesis pathways, including dehydrogenation and β-oxidation. However, ethyl heptanoate is formed in the aromatic compound degradation pathway under the action of alcohol acyltransferases (AAT). n-Hexanol is formed by the reduction of C6 aldehydes under the catalysis of lipoxygenase (LOX) and is an important source of the grassy aroma of grapes.

[0016] Furthermore, the method enhances the aroma of grapes by increasing the content of any one or more of hexyl acetate, β-ionone, caprylic acid, nonanoic acid, α-terpineol, and geraniol in the grape berries.

[0017] In another aspect, the present invention provides the use of strigolactone in the preparation of reagents that increase the content of volatile aroma substances in fruits, thereby enhancing the aroma of fruits.

[0018] Furthermore, the volatile aroma substances include any one or more of hexyl acetate, β-ionone, caprylic acid, nonanoic acid, α-terpineol, and geraniol.

[0019] Furthermore, the concentration of the strigolactone is 0.5-4 μmol / L.

[0020] Furthermore, the fruit is a grape.

[0021] In another aspect, the present invention provides the use of strigolactone in the preparation of reagents that alter the aroma of grapes, wherein the concentration of strigolactone is 0.5-4 μmol / L.

[0022] The present invention has the following beneficial effects:

[0023] 1. By treating grape berries with methyl jasmonate, phenylalanine, and strigolactone, it was found that the exogenous spraying of these three plant growth regulators can significantly increase the content of organic compounds such as acids, esters, and terpenes in grape berries. This provides a theoretical basis for enriching the aroma characteristics of grapes, improving the stress resistance of grape berries, and extending the postharvest shelf life through exogenous plant hormone treatment.

[0024] 2. It was discovered that exogenous application of strigolactone can significantly alter the aroma of fresh Muscat grapes, increasing the content of substances such as hexyl acetate, β-ionone, caprylic acid, nonanoic acid, α-terpineol, and geraniol. This provides a new technical means for improving the aroma quality of aromatic grapes and offers a reference for subsequent research on the effects of strigolactone on fruit quality. Attached Figure Description

[0025] Figure 1 The figures show the OPLS-DA analysis and model cross-validation results for grape berries treated with different exogenous plant growth regulators. Figure A shows the OPLS-DA analysis results, with the horizontal axis representing predicted principal components and the vertical axis representing orthogonal principal components. Samples of the same color represent samples from the same treatment group. Figure B shows the model cross-validation results. The model quality assessment criteria include three indicators: R²X, R²Y, and Q². R²X and R²Y represent the model's explanatory power for the independent variable X and dependent variable Y, respectively. Q² is calculated through cross-validation and is used to evaluate the model's predictive ability. Generally, Q² > 0.5 is considered a valid model, and Q² > 0.9 indicates a very good model. The two dashed lines represent the threshold line of R² = 1 and the trend line of Q² changes, respectively.

[0026] Figure 2 Heatmaps showing the differences in aroma components in grapes treated with different exogenous plant growth regulators. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to embodiments. It should be noted that the embodiments described below are intended to facilitate understanding of the present invention and are not intended to limit it in any way. The reagents used in this embodiment are all known products and were obtained by purchasing commercially available products.

[0028] Example 1: Aroma Characteristics Analysis of Grape Fruits Treated with Exogenous Plant Growth Regulators

[0029] To investigate the aroma characteristics of 'Hanxiangmi' grapes after treatment with different exogenous plant growth regulators, volatile components were extracted from grape samples treated with three different exogenous plant growth regulators using SH-SPME and analyzed by GC-MS. The specific methods are as follows:

[0030] I. Experimental Materials

[0031] In May 2024, five-year-old 'Hanxiangmi' grapevines with good growth and consistent growth were selected at Dicuiyuan Farm in Zhenhai District, Ningbo City (121°32′E, 29°59′N) for treatment with exogenous plant growth regulators.

[0032] II. Handling Methods

[0033] Fruits at the ripening stage were treated with exogenous plant growth regulators methyl jasmonate (Solepro, model IM5630), strigolactone (Solepro, model SS5720), strigolactone inhibitor (Solepro, model IT1220), and phenylalanine (Solepro, model P0010). Three plants were treated per treatment, with at least five clusters of fruit per plant. Fruits were harvested after ripening, transported to the laboratory at low temperature, and stored at -80°C. The treatment method is shown in Table 1. The solution was sprayed evenly onto the entire cluster using a sprayer until the surface droplets reached a critical state and began to flow steadily downwards. In the analysis of the determination results, M1500 and M2000 represent treatments with methyl jasmonate at concentrations of 1500 μmol / L and 2000 μmol / L, respectively; G0.5, G1, G2, and G4 represent treatments with strigolactone at concentrations of 0.5 μmol / L, 1.0 μmol / L, 2.0 μmol / L, and 4.0 μmol / L, respectively; T1 represents treatments with strigolactone inhibitor at concentrations of 1.0 μmol / L; and P60 and P140 represent treatments with phenylalanine at concentrations of 60 mg / L and 140 mg / L, respectively.

[0034] Table 1. Experimental treatment concentrations and methods

[0035]

[0036] III. GC-MS Measurement

[0037] Sixty g of each of the 'Hanxiangmi' grape samples sprayed with three different exogenous plant growth regulators were ground, centrifuged, and filtered to obtain clear juice. The grape juice was transferred to 20 mL Agilent bottles (Agilent Technologies, Santa Clara, USA) equipped with a magnetic stir bar and 1.5 g NaCl, using 2-octanol as an internal standard, and sealed with a clamp cap equipped with a silicone cap. Using the HS-SPME method, the sample bottles were equilibrated at 50°C for 10 minutes, then a solid-phase microextraction head (solid-phase microextraction fiber, 50 / 30 μM DVB / CAR / PDMS, Superco, Belfont, USA) was inserted, and volatile aromatic compounds were extracted at 50°C for 30 minutes. Then, the sample was inserted into the inlet of a chromatograph (Agilent 8890 GC, Agilent Technologies), desorbed at 260°C for 3 minutes without separation mode, and equipped with a 5977 mass selection detector (Agilent Technologies). Each treatment was repeated three times, and the average value was taken.

[0038] The GC conditions were as follows: an HP-INNOWAX column (30 mm × 0.25 mm × 0.25 μm; Agilent Technologies) was used; the carrier gas was 99.99% helium, with a flow rate of 1 mL / min; the column temperature was maintained at 40℃ for 5 minutes, increased to 240℃ at a rate of 5℃ / min, and then increased to 260℃ at a rate of 20℃ / min and held for 5 minutes.

[0039] MS conditions: mass transfer line temperature and ionization source temperature were 260℃ and 230℃, respectively. Electron impact mass spectrometry data were collected in the range of 20–400 m / z at an ionization voltage of 70 eV.

[0040] IV. Data Processing

[0041] GC-MS results were obtained by qualitatively identifying volatile compounds in the samples using the NIST / EPA / NIH mass spectrometry library (NIST2014). Quantitative analysis was performed by comparing the peak areas with internal standards to determine the content of aroma components, expressed in μg / g: Aroma component content = Aroma component peak area × Internal standard content / Internal standard peak area. Data were compiled and processed using Microsoft Office, and the mean and standard deviation were calculated.

[0042] Heatmaps were generated using TBtools. Principal component analysis (PCA) results were extracted and visualized using SIMCA 14.1, and orthogonal partial least squares-discriminant analysis (OPLS-DA) was performed to calculate the variable importance in projection (VIP). Image processing was performed using Adobe Illustrator 2022.

[0043] V. Aroma Characteristics Analysis

[0044] Table 2 shows that 39 common effective volatile aroma compounds were detected in the strigolactone (SL) treatment group, with increased contents of acids, alcohols, aldehydes, esters, and monoterpenes compared to the CK group. In both the SL and its inhibitor treatment groups, these compounds were upregulated to varying degrees. The changes in substances were particularly significant in the G2, G4, and T1 treatment groups, indicating that SL may have a strong inducing effect in regulating grape fruit aroma synthesis. Especially in the accumulation of esters and terpenes, SL treatment showed a significant increase, suggesting that it may enhance the activity of related metabolic pathways by regulating carbon flux distribution and interactions between signaling pathways (such as interactions with hormones like JA and ABA), thereby promoting aroma compound synthesis.

[0045] As shown in Table 3, 48 common effective aroma compounds were detected in the methyl jasmonate (MeJA) treatment group, the most diverse group among the three treatments, including 6 acids, 3 alcohols, 7 aldehydes, 9 esters, 6 ketones, and 15 terpenes. Compared with the control group (CK), the MeJA treatment significantly increased the overall VOC content in grape berries, especially in aldehydes, acids, esters, and terpenes. This indicates that MeJA, as a signaling molecule, has a broad and strong regulatory role in inducing plant secondary metabolism. Notably, representative terpene aromatic compounds such as geraniol, nerol, and nerol were not detected in the CK control group, but accumulated significantly in the MeJA treatment group. It is speculated that they may participate in aroma synthesis by activating the expression of key enzyme genes (such as GPPS and TPS) in terpene synthesis pathways (such as MVA and MEP pathways). Furthermore, the significant increase in terpenoid compounds may also be related to the enhanced activity of MeJA-induced transcription factors (such as MYC2), which further drives the reprogramming of the terpenoid secondary metabolic network.

[0046] In the phenylalanine (Phe) treatment group, a total of 36 common effective aroma compounds were detected, covering 6 major volatile compounds, including 6 acids, 2 alcohols, 5 aldehydes, 10 esters, 6 ketones, and 11 terpenes. Compared with the control group, Phe treatment significantly altered the content of some aroma components. Acetic acid was not detected in the treatment group, indicating that it may have been inhibited or converted and consumed. Among aldehydes, nonanal content increased significantly, presumably related to enhanced fatty acid β-oxidation. Esters and ketones generally showed an increasing trend, suggesting that Phe may promote esterification and secondary metabolite synthesis in fruits by regulating intermediate metabolic pathways. However, the overall content of terpenes did not change significantly, indicating that Phe's regulatory effect on terpene synthesis pathways is relatively weak.

[0047] Table 2. Aroma compounds of grapes after treatment with strigolactones

[0048]

[0049]

[0050] Table 3. Aroma compounds of grapes after treatment with methyl jasmonate and phenylalanine

[0051]

[0052]

[0053] In summary, all three exogenous plant growth regulators affected the composition and content of volatile aroma compounds in 'Hanxiangmi' grapes to varying degrees. MeJA treatment had the most significant effect on increasing the types and content of aroma compounds in the overall fruit, particularly the significant accumulation of terpenes, which may make an important contribution to enhancing the floral and fruity aroma characteristics. Phe treatment mainly promoted the synthesis of fatty acid derivatives such as esters and ketones, while having a smaller impact on terpenes. SL treatment showed a synergistic increase in multiple types of aroma compounds, possibly affecting the aroma metabolism network through a synergistic regulatory mechanism with multiple hormonal pathways.

[0054] Example 2: Aroma Component Difference Analysis

[0055] To further analyze the effects of three exogenous plant growth regulators on fruit aroma compounds in this experiment, the common aroma components of different exogenous plant growth regulators were used as the dependent variable, and the different treatment concentrations were used as the independent variables. The effects were analyzed using OPLS-DA (…). Figure 1 A) in the above method can effectively distinguish grape samples treated with three exogenous plant growth regulators. The fit indices of the independent variables in this analysis are (R0, R ... 2 x) was 0.948, and the dependent variable fit index was (R) 2 y) is 0.999, and the model prediction exponents are respectively (Q 2 The value is 0.798, R 2 and Q 2 A value greater than 0.5 indicates an acceptable model fit. After 200 permutation tests, if... Figure 1 As shown in B, this indicates that the model does not overfit and the model validation is effective. Therefore, the result can be used for the differential identification analysis of grape aroma in this experiment.

[0056] The three treatment groups of grape samples showed similar aroma components, but the total content of each type of substance differed. The aroma components with the highest content were acids, followed by esters and terpenes. The ester compound content in the methyl jasmonate and phenylalanine treatment groups was significantly higher than that in the strigolactone treatment group, while the acid content in the strigolactone treatment group was significantly higher than that in the other two treatment groups.

[0057] To further analyze the contribution rate of different aroma components in fruits treated with different exogenous plant growth regulators, based on the data analysis structure of this embodiment, 17 differential aroma substances were screened out using the criteria of P < 0.05 and VIP > 1. Figure 2The study included 1 type of alcohol, 3 types of acids, 2 types of esters, 2 types of aldehydes, 3 types of ketones, and 6 types of terpenes. The heatmap shows that the control group had the highest content of 7 components: valeric anhydride, citronellol, decanal, n-hexanol, isophthalaldehyde, acetic acid, and 3-hydroxy-2-butanone. The methyl jasmonic acid treatment group had the highest content of 10 components: nerol, n-hexanol, geraniol, hexyl acetate, caprylic acid, β-damascene, acetic acid, ethyl heptaate, citronellol, and isophthalaldehyde. The strigolactone treatment group had the highest content of 7 components: hexyl acetate, β-ionone, caprylic acid, nonanoic acid, acetic acid, geraniol, and α-terpineol. The six components with the highest content in the phenylalanine treatment group were ethyl heptanate, 3-hydroxy-2-butanone, eucalyptol, α-terpineol, isophthalaldehyde and β-ionone.

[0058] The results show that the methyl jasmonate treatment group had significantly higher levels of nerol, n-hexanol, and β-damascene than other groups, enhancing the intensity of the Muscat aroma. In the strigolactone treatment group, the levels of hexyl acetate, β-ionone, and nonanoic acid were significantly higher than other groups. Based on the characteristics of hexyl acetate, β-ionone, and nonanoic acid, hexyl acetate and nonanoic acid can inhibit the germination of fungal spores, thereby improving the fruit's disease resistance. Hexyl acetate also has a sweet fruity aroma. β-ionone belongs to the C13-norisoprene class and has violet and woody notes; its increased content enhances the complexity of the 'Hanxiangmi' aroma. Furthermore, the antioxidant properties of β-ionone can reduce oxidative damage to the grape fruit. The strigolactone treatment increased the complexity of the grape's aroma profile, transforming Muscat grapes into a complex aroma profile of floral, grassy, ​​and fruity notes, with rich layers of fragrance. The effect of phenylalanine was not significant. In conclusion, based on production needs, the application of strigolactones in table grapes, wine grapes, and grape stress management will significantly improve the flavor and quality of grapes.

[0059] Example 3: OAV analysis of differential aromas

[0060] Odor activity value (OAV) determines the ratio of the concentration of a single volatile compound to its odor threshold in water or air, allowing for the study of the contribution of potential key aroma compounds in grapes to the overall aroma of the fruit. The level of aroma components alone is not sufficient to determine the aroma characteristics of grapes; typically, it is the aroma components with high OAV that characterize the grape aroma. Previous studies have evaluated the contribution of individual aromas to the overall aroma of grapes by calculating OAV. An OAV greater than 1 indicates that the aroma component has a certain influence on the grape aroma, while an OAV greater than 10 indicates that the aroma component contributes significantly to the overall aroma of the grape.

[0061] The aroma component thresholds and aroma descriptions, compiled from literature reports, are shown in Table 4. Furthermore, based on aroma difference analysis, dominant groups were further screened within the experimental groups, and the OAV (Original Aspect Ratio) of differential aroma components in grape fruits under different exogenous plant growth regulator treatments was calculated.

[0062] Table 4. Thresholds of differential aroma components and aroma descriptions of grape berries

[0063]

[0064] Table 5. Differential aroma components (OAV) of grapes under different treatments

[0065]

[0066] The results (Table 5) showed that the OAV values ​​of nonanoic acid, geraniol, and α-terpineol in the strigolactone treatment groups (G0.5, G1, G2, and G4) were greater than 1 and significantly increased, indicating that these substances may be key components affecting fruit aroma. Specifically, in group G2, octanoic acid was greater than 1 and significantly increased; in groups G0.5, G1, and G4, decanal, ethyl heptanoate, β-damascene, and eucalyptol were greater than 30 and significantly increased; and in groups G1 and G4, β-ionone was greater than 450 and significantly increased. This indicates that different concentrations of strigolactone specifically affect fruit aroma components. In the methyl jasmonic acid treatment groups (M1500 and M2000), the OAV values ​​of nonanoic acid, octanoic acid, n-hexanol, β-damascene, geraniol, and α-terpineol were greater than 1 and significantly increased; while decanal was less than 1 and significantly decreased; indicating that these substances may be key components affecting fruit aroma. Furthermore, the different concentrations of treatment showed no significant specificity. In the phenylalanine treatment groups (P60 and P140), the OAV values ​​of nonanoic acid and α-terpineol were greater than 1 and significantly increased; while those of citronellol were less than 1 and significantly decreased; indicating that these substances may be key components affecting fruit aroma due to phenylalanine. The OAV values ​​of the remaining substances were relatively small and showed no significant difference from the control (CK).

[0067] Compared with the control group, the strigolactone treatment group showed significantly higher OAV values ​​for decanal, ethyl heptanoate, β-ionone, β-damascene, α-terpineol, nonanoic acid, and geraniol, exhibiting floral and fruity aromas. Among these, ethyl heptanoate, β-ionone, and β-damascene had significantly higher OAV values ​​than 10, indicating that these substances contributed more significantly to the aroma characteristics of grapes. The methyl jasmonic acid treatment group showed relatively high OAV values ​​for hexanol, α-terpineol, geraniol, β-damascene, nonanoic acid, and caprylic acid, with hexanol and α-terpineol showing particularly high OAV values, indicating that these two substances played a more significant role in imparting floral and grassy aromas to grapes. In the phenylalanine treatment group, α-terpineol and nonanoic acid showed relatively high OAV values, exhibiting floral and grassy aromas. In summary, the results show that treating grapes with exogenous hormones such as strigolactone can not only regulate and transform the aroma of grapes, but also impart richer and more complex aroma characteristics, with better results than phenylalanine and methyl jasmonic acid. The effect is most significant when strigolactone at a concentration of 4.0 μmol / L is used. Therefore, in practical production applications, strigolactone treatment can be used to treat grapes to meet the needs of different consumer groups for table grapes or wine grapes.

[0068] In addition, to verify the feasibility of strigolactone in regulating the aroma characteristics of grapes, this invention further used six 'Hanxiangmi' grapevines from the same source as experimental materials for verification. The grape treatment methods, aroma substance determination, and analysis were the same as in Example 1, and the OAV values ​​of the different aroma substances in the different treatment groups were analyzed. The results showed that, consistent with the above results, the OAV values ​​of decanal, ethyl heptanoate, β-ionone, β-damascene, α-terpineol, and nonanoic acid in the grapes treated with strigolactone were significantly prominent, giving the grapes floral, grassy, ​​and fruity aromas. In the methyl jasmonic acid treatment group, the OAV values ​​of n-hexanol and α-terpineol were more prominent, giving the grapes floral and grassy aromas. In the phenylalanine treatment group, the OAV value of α-terpineol was relatively prominent, but its effect was not obvious. This proves that the aroma characteristics of grapes treated with different exogenous plant growth regulators are significantly different, and the aroma layers of grapes treated with strigolactone are richer.

[0069] The above results further demonstrate that there are significant differences in aroma transformation after treating grapes with methyl jasmonate, strigolactone, and phenylalanine: the effect of phenylalanine treatment is not obvious, methyl jasmonate enhances the floral aroma intensity of 'Hanxiangmi' grapes; strigolactone imparts characteristic aroma substances such as β-ionone and nonanoic acid to grapes, giving the treated grapes floral, fruity, and grassy aromas, with a more complex and richer aroma profile, showing significant advantages compared to the other two regulators.

[0070] Example 4: Comparison of the effects of different treatment methods

[0071] To investigate whether there are significant differences in the aroma compounds measured from grapes and their contribution to the overall aroma of the fruit after spraying the same exogenous plant growth regulator with different treatment methods, this example also compared the effects of spraying 'Hanxiangmi' grapes with treatments shown in Table 6, namely spraying the bunches, inflorescences, or leaves. The methods for measuring and analyzing the aroma compounds and OAV values ​​of the grapes after different treatments were the same as in Examples 1-3, and the experimental materials were from the same source as in Example 1. The OAV value analysis results of 'Hanxiangmi' grapes after different treatments are shown in Tables 7-9.

[0072] Table 6. Experimental treatment concentrations and methods

[0073]

[0074] Table 7. Differential aroma components (OAV) in grape berries after spraying with exogenous plant growth regulators on grape bunches.

[0075]

[0076] Table 8. Differential aroma components (OAV) in grape berries after application of exogenous plant growth regulators to the inflorescence.

[0077]

[0078] Table 9. Differential aroma components (OAV) in grape berries after foliar application of exogenous plant growth regulators.

[0079]

[0080] The results in Tables 7-9 show that when the same exogenous plant growth regulator was sprayed on grape bunches, inflorescences, and leaves, the OAV values ​​of aroma compounds measured in grape berries differed significantly. The OAV values ​​of aroma compounds in grape berries sprayed on inflorescences or leaves were generally lower than those sprayed on grape bunches. For example, with strigolactone, the OAV value of acetic acid decreased to 0 when sprayed on inflorescences and leaves, and the OAV value of α-terpineol decreased to below 10. Aroma compounds with prominent OAV values, such as ethyl heptanoate and β-ionone, also showed significant decreases compared to grape berries sprayed on bunches. This indicates that spraying the bunches is the most effective way to improve the aroma characteristics of the berries.

[0081] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A reagent for regulating the aroma of grapes, characterized in that, Including any one or more exogenous plant growth regulators among methyl jasmonate, phenylalanine, and strigolactone.

2. The reagent as described in claim 1, characterized in that, The exogenous plant growth regulator is strigolactone.

3. The reagent as described in claim 2, characterized in that, The concentration of the strigolactone is 0.5-4 μmol / L.

4. A method for regulating the aroma of grapes, characterized in that, Grapes are treated with the reagent described in any one of claims 1-3.

5. The method as described in claim 4, characterized in that, The aroma of grapes can be enhanced by increasing the content of any one or more of hexyl acetate, β-ionone, caprylic acid, nonanoic acid, α-terpineol, and geraniol in the grape berries.

6. The use of strigolactones in the preparation of reagents that increase the content of volatile aroma compounds in fruits, thereby enhancing the aroma of the fruits.

7. The use as described in claim 6, characterized in that, The volatile aroma substances include any one or more of hexyl acetate, β-ionone, caprylic acid, nonanoic acid, α-terpineol, and geraniol.

8. The use as described in claim 7, characterized in that, The concentration of the strigolactone is 0.5-4 μmol / L.

9. The use as described in claim 8, characterized in that, The fruit in question is a grape.

10. The use of strigolactones in the preparation of reagents for altering the aroma of grapes, characterized in that, The concentration of the strigolactone is 0.5-4 μmol / L.

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