Preservative for pitaya and preservation method thereof

Abstract

The application discloses a pitaya fresh-keeping agent and a fresh-keeping method thereof, and belongs to the field of postharvest fresh-keeping technology of fruits and vegetables. The fresh-keeping agent comprises an active ingredient of fluroxypyr-methyl, and optionally further comprises a bactericide of prochloraz. The fresh-keeping method comprises soaking postharvest pitaya in a solution containing 10-200 mg / L of fluroxypyr-methyl for 1-5 minutes, and then storing after air-drying. Experiments prove that the fresh-keeping agent can significantly delay the yellowing and aging of pitaya scales (calyx), and can also cooperatively reduce the fruit rot rate and prolong the shelf life by 7-10 days when the fresh-keeping agent is compounded with prochloraz. Compared with the prior art, the fluroxypyr-methyl is applied to the fresh-keeping of pitaya for the first time, and has the advantages of remarkable fresh-keeping effect, safety and low toxicity, environmental friendliness and the like.

Description

Technical Field

[0001] This invention relates to the field of postharvest preservation technology for fruits and vegetables, specifically to a dragon fruit preservative and its preservation method. Background Technology

[0002] Dragon fruit (Hylocereus spp.) is an important economic fruit in tropical and subtropical regions, beloved by consumers for its unique appearance, rich nutritional value, and excellent taste. However, dragon fruit undergoes vigorous physiological metabolism after harvest, and its peel lacks a dense protective structure, making it extremely susceptible to water loss and wilting. In particular, the scales (calyx) of the dragon fruit rapidly yellow and dry out during post-harvest storage, severely impacting the fruit's appearance and marketability. Furthermore, dragon fruit is highly susceptible to pathogens such as anthracnose and soft rot after harvest, leading to fruit decay and significant economic losses.

[0003] Currently, post-harvest preservation of dragon fruit mainly employs a combination of low-temperature refrigeration and chemical preservatives. Commonly used chemical preservatives are primarily fungicides such as imazalil, focusing on controlling rot, but their effect on delaying scale yellowing is limited. Although some studies have attempted to use plant growth regulators such as 2,4-dichlorophenoxyacetic acid (2,4-D) to delay senescence, 2,4-D poses potential safety and environmental risks, and its use is increasingly restricted (the EU has explicitly restricted the use of 2,4-D in fruit preservation). Therefore, developing a safe and environmentally friendly preservative specifically for dragon fruit that can effectively prevent decay, delay scale senescence, and is also environmentally friendly is of significant practical importance. Summary of the Invention

[0004] This invention aims to provide a dragon fruit preservative and its preservation method, which aims to solve the problem of yellowing and aging of dragon fruit scales (calyx) after harvest, and optionally solve the problem of fruit rot at the same time, thereby extending the shelf life of dragon fruit.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides the application of isooctyl clopyralid in delaying the yellowing of dragon fruit scales.

[0007] To further clarify, the mass concentration of the isooctyl chlorpyrifos is 25-100 mg / L.

[0008] The present invention also provides a dragon fruit preservative, wherein the preservative comprises isooctyl clopyralid and a bactericide.

[0009] To further clarify, the fungicide is selected from one or more of imazalil, pyraclostrobin, and thiamethoxam.

[0010] To further clarify, the bactericide is imazalil, the mass concentration of isooctyl clopyralid is 25-100 mg / L, and the mass concentration of imazalil is 100-500 mg / L.

[0011] To further clarify, the mass concentration of isooctyl chlorpyrifos is 50 mg / L, and the mass concentration of imazalil is 125 mg / L.

[0012] The present invention also provides a method for preserving dragon fruit using the above-mentioned preservative, comprising the following steps: soaking the harvested dragon fruit in a diluted preservative solution for 1-5 minutes, removing it and air-drying it naturally, and then packaging and storing it.

[0013] To further clarify, the soaking time is 2-3 minutes; the storage is room temperature storage or low temperature refrigeration.

[0014] The present invention also provides the application of the dragon fruit preservative in simultaneously delaying the yellowing of dragon fruit scales and reducing the fruit rot rate.

[0015] The present invention also provides the application of isooctyl clopyralid in enhancing the activity of prochloraz-induced defense enzymes in dragon fruit, said defense enzymes including chitinase and β-1,3-glucanase.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects:

[0017] This application is the first to apply isooctyl clopyralid to dragon fruit preservation: In the prior art, isooctyl clopyralid is only used for citrus preservation; this invention applies it to dragon fruit, solving the specific problem of yellowing scales, thus constituting a use-transfer invention. Experiments show that isooctyl clopyralid treatment significantly delays yellowing of dragon fruit scales; after 12 days of storage, the yellowing index is reduced by more than 58% compared to the control group, with effects comparable to or even better than 2,4-D. The combination of isooctyl clopyralid and imazalil not only maintains excellent green preservation but also significantly reduces fruit rot, achieving the dual functions of "green preservation" and "anti-rot." Colby's method calculations show that the optimal combination (50 mg / L + 125 mg / L) has a synergistic coefficient of 1.20-1.56 for scale yellowing and a synergistic coefficient as high as 1.22-2.22 for rot, demonstrating a significant synergistic effect. Isooctyl clopyralid is far less toxic than 2,4-D and readily degrades in soil (half-life 3.80-8.20 days), meeting the requirements for green food production. The research protocol in this application only requires soaking treatment, is simple to operate, low in cost, and easy to promote. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] The applicant has conducted the following research on the technical results of this application, specifically in the form of studies in Examples 1, 2, and 3.

[0020] Example 1: The effect of isooctyl clopyralid on delaying yellowing of dragon fruit scales

[0021] 1. Materials and Methods

[0022] Test materials: The dragon fruit variety used was 'Jindu No. 1', harvested from an orchard in Nanning, Guangxi, at commercial maturity (80% peel reddening). Fruits of uniform size, without mechanical damage, and free from pests and diseases were selected for the experiment. Wogan tangerines (control) were also used, with commercially mature fruits free from mechanical damage and pests and diseases.

[0023] Reagents: Clopyralid isooctyl ester technical grade (purity 95%), 2,4-D technical grade (purity 98%), anhydrous ethanol (co-solvent).

[0024] Preservative preparation:

[0025] Control group (CK): treated with clean water.

[0026] Treatment group 1 (XYZ-25): Prepare a solution containing 25 mg / L of isooctyl clopyralid.

[0027] Treatment group 2 (XYZ-50): Prepare a solution containing 50 mg / L of isooctyl clopyralid.

[0028] Treatment group 3 (XYZ-100): Prepare a solution containing 100 mg / L of isooctyl clopyralid.

[0029] Treatment group 4 (2,4-D): A solution containing 50 mg / L of 2,4-D was prepared (positive control).

[0030] Treatment methods: (1) Dragon fruit: 30 fruits per group, repeated 3 times. The fruits were completely immersed in the corresponding solution for 3 minutes, then removed and air-dried at room temperature. They were then placed in plastic baskets, covered with 0.02mm thick PE bags to keep them moist, and stored at 25℃ and 70-80% relative humidity. (2) Wogan oranges: 30 fruits per group, repeated 3 times. The fruits were completely immersed in the corresponding solutions of the control group, treatment groups 1, 2, 3, and 4 for 3 minutes, then removed and air-dried at room temperature. They were then placed in plastic baskets, covered with 0.02mm thick PE bags to keep them moist, and stored at 25℃ and 70-80% relative humidity.

[0031] Indicator Measurement and Methods:

[0032]

[0033] The scale yellowing index is as follows: Level 0: All scales are green; Level 1: Yellowing area at the scale tip <25%; Level 2: Yellowing area 25%-50%; Level 3: Yellowing area 51%-75%; Level 4: Yellowing area >75% or completely dried out. Yellowing index = Σ(Number of scales in each level × Level) / (Total number of scales × 4) × 100.

[0034] 2. Results and Analysis

[0035] Table 1. Effects of different concentrations of isooctyl clopyralid on yellowing of dragon fruit scales (after 12 days of storage).

[0036]

[0037] As shown in Table 1, after 12 days of storage, the scales of the water control (CK) group were severely yellowed, with a yellowing index as high as 78.5%.

[0038] Treatment with isooctyl clopyralid at various concentrations significantly delayed scale yellowing in a concentration-dependent manner. The yellowing index was 45.3% at 25 mg / L, while it was 32.5% and 30.8% at 50 mg / L and 100 mg / L, respectively, with no significant difference between the two treatments.

[0039] The greening effect of clopyralid isooctyl ester treatment at 50 mg / L was better than that of 2,4-D treatment at 50 mg / L, indicating that clopyralid isooctyl ester is as effective as or even better than 2,4-D in delaying the yellowing of dragon fruit scales.

[0040] Table 2. Effects of different concentrations of isooctyl clopyralid on yellowing of the stem of Wogan mandarin orange (after 12 days of storage).

[0041]

[0042] Between the two varieties, the yellowing index of scales in the dragon fruit CK group reached 78.5%, while the yellowing index of the fruit stem in the citrus CK group was about 58.1%. This indicates that the natural degree of yellowing of dragon fruit scales is much higher than that of citrus fruit stem aging, and dragon fruit is significantly more difficult to preserve than citrus.

[0043] XYZ-50 reduced the yellowing index from 78.5% to 32.5% in dragon fruit, an absolute decrease of 46.0 percentage points; and the absolute decrease in citrus was 25.6 percentage points. The absolute decrease in dragon fruit (46.0%) was significantly greater than that in citrus (25.6%), approximately 1.8 times that of citrus, indicating that isooctyl clopyralid has stronger preservative activity in dragon fruit, exceeding expectations based on citrus data.

[0044] XYZ-50 achieved a saturation effect on dragon fruit, while citrus fruits may require a higher concentration to achieve the same relative effect, indicating that dragon fruit is more sensitive to this substance.

[0045] Moisture content is a direct physiological indicator of the freshness of dragon fruit scales (the early stage of scale yellowing is manifested by moisture loss).

[0046] Table 3 Moisture content (after 12 days of storage)

[0047]

[0048] Based on the above research findings, our research team discovered that XYZ-50 increased the scale moisture content of dragon fruit from 52.3% to 68.5% (an increase of 16.2 percentage points), significantly outperforming 2,4-D. The absolute moisture content of citrus fruits was already high, limiting the potential for improvement to only about 3-5 percentage points. In contrast, the moisture retention effect on dragon fruit was approximately 3-5 times that of citrus fruits, representing a qualitative difference.

[0049] Table 4 Chlorophyll Content

[0050]

[0051] The above research data shows that the chlorophyll degradation rate of dragon fruit scales in the control group (CK) was much higher than that in citrus. After XYZ-50 treatment, the chlorophyll content of dragon fruit scales recovered to 0.38 mg / g, approximately 3.2 times that of the control group (CK); while in citrus, it was approximately 1.7 times that of the control group (CK). The significant difference in chlorophyll retention indicates that isooctyl clopyralid has a much higher activity in dragon fruit than in citrus.

[0052] Dragon fruit's high respiration rate is its main physiological characteristic, which places higher demands on the effectiveness of preservatives.

[0053] Table 5 Respiratory Intensity

[0054]

[0055] Table 6 Weight Loss Rate

[0056]

[0057] The research data above shows that the weight loss rate of dragon fruit (CK) was as high as 18.5%, approximately 2.2 times that of citrus (CK), indicating that water loss in dragon fruit is far more severe than in citrus. XYZ-50 reduced the weight loss rate of dragon fruit from 18.5% to 9.5%, an absolute reduction of 9.0 percentage points; while in citrus, it only reduced it by about 2.0 percentage points. The interspecies difference in the reduction of weight loss rate was as high as 4.5 times, indicating that the effect of clopyralid isooctyl ester on dragon fruit significantly exceeded expectations based on citrus data.

[0058] Table 7 ADH / PDC enzyme activity

[0059]

[0060] The above research data shows that the ADH / PDC activity in the dragon fruit CK group was significantly higher than that in citrus, indicating that dragon fruit has more vigorous postharvest ethanol metabolism and a more severe off-flavor problem. XYZ-50 reduced ADH activity by 60% in dragon fruit, but only about 42% in citrus, showing a significant difference in inhibition efficiency. The difference in enzyme activity inhibition effect indicates that isooctyl clopyralid has a stronger mechanism of action in dragon fruit.

[0061] Table 8 Ethanol Content

[0062]

[0063] The research data above shows that the ethanol content in dragon fruit (CK) (0.95 mg / g) is approximately 2.1 times that of citrus (0.45 mg / g). XYZ-50 reduced the ethanol content in dragon fruit by 63.2%, while it only reduced it by about 38% in citrus, with absolute reductions of 0.60 vs. 0.17 mg / g, representing a 3.5-fold difference in efficacy. This difference far exceeds reasonable expectations that a person skilled in the art could make based on citrus ethanol metabolism data.

[0064] Table 9 MDA Content

[0065]

[0066] The above research data shows that the degree of membrane lipid peroxidation in dragon fruit (CK) is about twice that of citrus, reflecting more severe post-harvest senescence stress in dragon fruit. XYZ-50 reduced MDA content by 50.4% in dragon fruit, but only about 23% in citrus. The interspecies differences in membrane protection effects further demonstrate species specificity.

[0067] Table 10 SOD Activity

[0068]

[0069] The above research data further demonstrates the specificity of the interspecies differences in antioxidant enzyme activation effects. The antioxidant enzyme activity in dragon fruit (CK) was lower than that in citrus, indicating a weaker natural antioxidant system and a greater dependence on preservatives. XYZ-50 increased SOD activity in dragon fruit by 46.8%, an absolute increase of 40 U / g; in citrus, it only increased by about 18%, an absolute increase of 21.5 U / g.

[0070] Example 2: Synergistic preservation effect of clopyralid isooctyl ester and imazalil

[0071] 1. Materials and Methods

[0072] 1.1 Test materials: The dragon fruit variety used in the test was 'Jindu No. 1'. The fruits were harvested from an orchard in Nanning, Guangxi, when they were commercially mature (80% of the peel turned red). Fruits of uniform size, without mechanical damage, and free from pests and diseases were selected for the experiment.

[0073] Isooctyl clopyralid (purity ≥97%) was purchased commercially; imazalil (purity ≥98%) was purchased commercially; all other reagents were of analytical grade.

[0074] 1.2 Preparation of preservatives:

[0075] Table 11 Design of different concentration ratios

[0076]

[0077] 1.3 Treatment method: The dragon fruit was completely immersed in the preservative solution for 3 minutes, then removed and air-dried naturally. It was then placed in a polyethylene preservation bag (0.03 mm thick), the bag was sealed tightly, and stored in a constant temperature incubator at (25±1)℃ and 75%~80% relative humidity. Each treatment group had 3 replicates, with 15 fruits in each replicate.

[0078] 1.4 Experimental Design

[0079] 1.4.1 Screening of synergistic effects of different concentration ratios

[0080] Nine compound combinations and corresponding single-agent controls were set up, as detailed in Table 11. After 14 days of storage, the scale yellowing index and decay rate were measured, and the inhibition rate and Colby's expected inhibition rate of each treatment were calculated to screen the optimal synergistic ratio.

[0081] 1.4.2 Dynamic synergistic effect of optimal ratio

[0082] Based on the optimal ratio (XYZ 50 mg / L + imazalil 125 mg / L) screened in Experiment 1.4.1, four treatments were set up: CK (water), XYZ single agent (50 mg / L), imazalil single agent (125 mg / L), and compound group (50 + 125 mg / L). Samples were taken on the 7th, 14th, 21st, and 28th days of storage to determine various quality indicators.

[0083] 1.4.3 Physiological Mechanism Analysis of Synergistic Effect

[0084] Using the four treatments described in Experiment 1.4.2, fruit peel samples were collected on the 14th day of storage (flash-frozen in liquid nitrogen and stored at -80℃) to determine the following enzyme activities and physiological indicators:

[0085] ADH (alcohol dehydrogenase) and PDC (pyruvate decarboxylase) activities: determined by spectrophotometry, unit U / g protein.

[0086] Chitinase and β-1,3-glucanase activities: determined by colorimetric method, unit U / g protein.

[0087] Malondialdehyde (MDA) content: determined by the thiobarbituric acid method, unit nmol / g.

[0088] Superoxide dismutase (SOD) and peroxidase (POD) activities were determined using the nitroblue tetrazolium method and the guaiacol method, in units of U / g protein.

[0089] 1.5 Methods for determining the index

[0090] Scale yellowing index: A grading system was used. Grade 0: Bright green scales, no yellowing; Grade 1: Slight yellowing at the scale tips (yellowing area <25%); Grade 2: Half of the scale is yellowed (25%~50%); Grade 3: Most of the scale is yellowed (50%~75%); Grade 4: Scales are completely yellowed or withered (>75%). Calculated using the following formula:

[0091] Yellowing index = ∑(Grade number × Number of fruits at that grade) / (4 × Total number of fruits) × 100%

[0092] Rot rate: Calculated based on the following formula for fruits showing obvious lesions, soft rot, or mold:

[0093] Rot rate (%) = (Number of rotten fruits / Total number of fruits) × 100%

[0094] Weight loss rate: The weight loss rate is calculated using a weighing method, with the initial weight of the fruit before storage as the initial weight. The formula is as follows:

[0095] Weight loss rate (%) = (Initial weight - Weight at measurement) / Initial weight × 100%

[0096] Marketable fruit rate: Fruits without rot, with a scale yellowing index ≤2, and without severe water loss and wilting are considered marketable fruits. The calculation formula is as follows:

[0097] Marketable fruit rate (%) = (Number of marketable fruits / Total number of fruits) × 100%

[0098] 1.6 Data Analysis Methods

[0099] The Colby method was used to evaluate the synergistic effect of the combination. Let A be a single agent of XYZ, and B be a single agent of imazalil. The expected inhibition rate E was calculated using the following formula:

[0100] E=X A +X B -(X) A ×X B ) / 100

[0101] Where X A and X BThe measured inhibition rates (%) of single agents A and B are shown below. The synergy coefficient SR = measured inhibition rate / expected inhibition rate. SR > 1.2 indicates significant synergy, and SR > 1.5 indicates highly significant synergy.

[0102] One-way ANOVA was performed using SPSS 26.0 software. Tukey HSD multiple comparison test was used to determine differences between groups, and the significance level was set at p < 0.05.

[0103] 2 Results and Analysis

[0104] 2.1 Screening of synergistic effects of different concentration ratios

[0105] The results of the scale yellowing index and decay rate determination for each treatment after 14 days of storage are shown in Table 12.

[0106] Table 12 Screening of synergistic effects of different concentration ratios (stored for 14 days)

[0107]

[0108] Note: Data in the table are mean ± standard deviation (n=3); different lowercase letters in the same column indicate significant differences (p<0.05).

[0109] The expected inhibition rate and synergistic coefficient of Colby were calculated for each compound combination in Table 12, and the results are shown in Table 13.

[0110] Table 13 Synergistic coefficients of different compound combinations (stored for 14 days)

[0111]

[0112] Table 13 shows the synergistic effect on scale yellowing: the SR values ​​of the combinations C1 (25+125), C2 (25+250), and C4 (50+125) were 1.55, 1.39, and 1.20, respectively, all greater than 1.2, indicating significant synergy. C1 showed the strongest synergy, but C4 had a lower measured yellowing index, resulting in a better overall effect. Regarding the synergistic effect on decay rate: the SR values ​​of C4 (50+125) and C7 (100+125) were as high as 1.74 and 1.65, respectively, showing extremely significant synergy; while the SR value of the combination with high-concentration prochloraz (≥250 mg / L) was close to 1, indicating no significant synergy. This suggests that when low-concentration prochloraz (125 mg / L) is combined with XYZ, XYZ can significantly enhance the disease prevention effect of prochloraz. Based on comprehensive comparison, C4 (XYZ 50 mg / L + prochloraz 125 mg / L) was selected as the optimal combination for subsequent experiments.

[0113] 2.2 Dynamic synergistic effect of optimal ratio

[0114] The optimal ratio (XYZ 50 mg / L + imazalil 125 mg / L) and each single agent were compared. The quality indicators were measured periodically during the storage period of 0-28 days. The results are shown in Table 14.

[0115] Table 14. Preservation effect of optimal ratio at different storage times

[0116]

[0117] Note: Different lowercase letters in the same column indicate significant differences between treatments at the same time point (p<0.05).

[0118] Colby synergy coefficients were calculated for the data in Table 14, and the results are shown in Table 15.

[0119] Table 15 Synergy coefficient (SR) of optimal ratio at different storage times

[0120]

[0121] Note: Expected values ​​are calculated using the Colby method, with CK as the baseline. For example, the 21-day yellowing inhibition rate: XYZ single-dose inhibition rate = (96.5-58.2) / 96.5 = 39.7%, prochloraz single-dose inhibition rate = (96.5-78.5) / 96.5 = 18.7%, expected = 39.7% + 18.7% - (39.7 × 18.7) / 100 = 52.9%.

[0122] As shown in Tables 14 and 15, after 7 days of storage, the yellowing index of the compound group was only 12.5%, which was significantly lower than that of XYZ single agent (25.3%) and imazalil single agent (40.1%), with a synergistic coefficient of 1.56; the rot rate was 1.7%, with a synergistic coefficient as high as 2.22, indicating that the compound group showed a strong synergistic effect in the early stage of preservation.

[0123] During storage for 14–28 days, the yellowing index of the compound group remained consistently between 26.7% and 48.0%, while that of XYZ single agent rose to 41.5%–75.0%, and that of prochloraz single agent rose to 65.3%–88.0%. The rot rate of the compound group was 6.7%–18.0%, significantly lower than that of prochloraz single agent (10.0%–40.0%). The synergy coefficient remained consistently above 1.20.

[0124] The commercial fruit rate of the compound group was still as high as 82.0% after 21 days, while that of XYZ single agent and prochloraz single agent was only 35.0% and 50.0%, respectively. With a commercial fruit rate of ≥80% as the criterion for acceptable shelf life, the shelf life of the CK group was about 7 days, the XYZ single agent group was about 10 days, the prochloraz single agent group was about 14 days, while the compound group could reach 21 days, indicating that the compound can significantly extend the commercial shelf life of dragon fruit by about 7 to 14 days.

[0125] 2.3 Physiological Mechanism Analysis of Synergistic Effect

[0126] The results of enzyme activity and physiological index measurements of the peels of each treatment on the 14th day of storage are shown in Table 16.

[0127] Table 16 Effects of different treatments on physiological indicators of dragon fruit peel (after 14 days of storage)

[0128]

[0129] Note: ADH and PDC activities are expressed as relative values ​​with CK = 100; the rest are measured values. Different lowercase letters in the same column indicate significant differences (p < 0.05).

[0130] Table 16 shows that studies on enzymes related to anaerobic metabolism revealed that the activities of ADH and PDC in both the XYZ single-dose and combined-dose groups were significantly lower than those in the CK group, while there was no significant difference between the imazalil single-dose and CK. The combined-dose group and the XYZ single-dose group showed comparable effects in inhibiting ADH / PDC, indicating that XYZ primarily played a role in delaying anaerobic metabolism, while imazalil had no interference.

[0131] Regarding the analysis of defensive enzyme activities, prochloraz alone significantly induced chitinase and β-1,3-glucanase activities (approximately 3.5 times that of CK), while in the combined group, the activities of these two enzymes further increased to 5.7 times and 5.7 times that of CK, respectively, significantly higher than those induced by prochloraz alone. This result indicates that XYZ can enhance prochloraz-induced systemic acquired resistance.

[0132] Regarding the analysis of membrane lipid peroxidation and antioxidant enzymes, the compound group had the lowest MDA content at 5.5 nmol / g, significantly lower than that of the individual agents, indicating that the compound can more effectively reduce membrane lipid peroxidation damage. The SOD and POD activities of the compound group were significantly higher than those of the individual agents, indicating that the compound group achieved synergistic enhancement of antioxidant defense capabilities.

[0133] In summary, through concentration gradient screening, the optimal combination of XYZ (50 mg / L) and prochloraz (125 mg / L) was determined. After 14 days of storage, this combination resulted in a scale yellowing index of 26.7%, a rot rate of 6.7%, and a marketable fruit rate of 88.0%, all significantly superior to the single-agent treatments. Colby's method calculations showed that the synergistic coefficient (SR) for scale yellowing of this combination ranged from 1.20 to 1.56, and the SR for rot rate ranged from 1.22 to 2.22. Particularly in the early storage period (7 days), the rot inhibition synergistic coefficient reached as high as 2.22, indicating an unexpected synergistic effect of XYZ and prochloraz. Physiological studies revealed that XYZ could further enhance the activity of prochloraz-induced defensive enzymes, while synergistically increasing the activity of antioxidant enzymes such as SOD and POD, and reducing MDA accumulation. The combined treatment group achieved the dual functions of maintaining green color and preventing decay, thus comprehensively improving the fruit preservation effect.

[0134] Example 3: Comparison of the effects of clopyralid isooctyl ester combined with different fungicides

[0135] 1. Materials and Methods

[0136] Test materials: Same as in Example 2.

[0137] Pyraclostrobin and imazalil are commercially available.

[0138] Experimental plan for the preparation of preservatives:

[0139] Table 17 Experimental Design

[0140]

[0141] The processing method is the same as in Example 2.

[0142] The detection indicators and methods are the same as in Example 2 (scale yellowing index, rot rate, weight loss rate and marketable fruit rate (the proportion of fruits with scale yellowing index ≤ 2 and no rot)).

[0143] One-way ANOVA was performed using SPSS 26.0. Post-hoc multiple comparisons were performed using the Tukey HSD test, with a significance level of α = 0.05. Data are expressed as mean ± standard deviation. The coefficient of synergy (SR) was calculated using the Colby method: SR = Measured inhibition rate / Expected inhibition rate, where expected inhibition rate = X% + Y% − (X% × Y%) / 100. SR > 1.2 was considered significant synergy, and SR > 1.5 was considered highly significant synergy.

[0144] 2. Results and Analysis

[0145] 2.1 Yellowing index and decay rate of scales in each treatment group after 14 days of storage

[0146] Table 18. Yellowing index and decay rate of scales in each treatment group after 14 days of storage.

[0147]

[0148] Table 19 Inhibition rates of each single agent relative to CK

[0149]

[0150] The expected inhibition rate and synergy coefficient (SR) of each combination were calculated using the Colby method, and the results are shown in Table 20-22.

[0151] Table 20. Calculation of Synergistic Coefficient of Imazalil Compound Group

[0152]

[0153] Table 21 Calculation of Synergistic Coefficient of Pyraclostrobin Compound Combinations

[0154]

[0155] Table 22 Calculation of Synergistic Coefficient of Imazalil Compound Groups

[0156]

[0157] From Tables 18-22, we can see that: (1) Synergistic effect on scale yellowing: X25Q250 and X25P125 performed well, but X50P125 had the lowest measured yellowing index (22.1%), and SR was close to 1.2, which is the critical value for significant synergy. (2) Synergistic effect on decay rate: X50P125 and X50Q125 both achieved extremely significant synergy, among which X50P125 had the lowest measured decay rate (4.2%), and the synergistic effect was the most stable. In summary, X50P125 performed best in both green preservation (yellowing inhibition) and decay prevention (decay inhibition), and prochloraz alone has good antibacterial activity. Therefore, prochloraz was selected as the optimal combination partner for XYZ.

[0158] 2.2 Weight loss rate and marketable fruit rate of each treatment group after 14 days of storage

[0159] Table 23 Weight loss rate and marketable fruit rate of each treatment group after 14 days of storage

[0160]

[0161] Table 23 shows that, regarding weight loss rate, the CK group had a weight loss rate as high as 12.3%, indicating severe post-harvest water loss in dragon fruit. All single-agent treatments reduced the weight loss rate, with XYZ showing a concentration-dependent effect. The combined treatment further reduced the weight loss rate, with the X50P125 group exhibiting the lowest rate at only 5.0%, significantly lower than any single agent (p < 0.05). This indicates that the combination of XYZ and prochloraz has a synergistic effect in maintaining fruit moisture, possibly related to their combined inhibition of respiration intensity and maintenance of scale structure integrity. Regarding marketable fruit rate, the CK group had a marketable fruit rate of only 32.5%, with the vast majority of fruits losing their commercial value due to scale yellowing or rotting. The marketable fruit rate of XYZ (X50) was 55.0%, and that of prochloraz (P125) was 48.3%, both significantly higher than the CK group. The X50P125 compound treatment group achieved a marketable fruit rate of 88.3%, the highest among all treatments and significantly superior to any single agent (p < 0.01). This indicates that the combination of XYZ and imazalil synergistically improves the overall marketability of dragon fruit, increasing the proportion of marketable fruit by nearly 2.7 times compared to the control (CK).

[0162] Optimal compound verification: X50P125 showed the best performance in both the weight loss rate (5.0%) and the marketable fruit rate (88.3%), further confirming that the "XYZ 50 mg / L + imazalil 125 mg / L" selected in Example 2 is the optimal compound solution.

[0163] 2.3 The effect of combining clopyralid isooctyl ester with high concentration of prochloraz (500 mg / L)

[0164] To further investigate the effect of prochloraz concentration on the synergistic effect, especially to verify whether the combination of low-concentration prochloraz (125 mg / L) and XYZ is superior to high-concentration single agent or high-concentration combination, this experiment added a combination treatment group of prochloraz 500 mg / L and XYZ (25, 50 mg / L) to the original design.

[0165] Add the following processing groups (other steps are the same as in 2.1):

[0166] X25P500: XYZ 25 ​​mg / L + imazalil 500 mg / L

[0167] X50P500: XYZ 50 mg / L + imazalil 500 mg / L

[0168] After 14 days of storage, the scale yellowing index, rot rate, weight loss rate, and marketable fruit rate were measured.

[0169] Table 24. Preservation effect of high-concentration imazalil compound group after 14 days of storage.

[0170]

[0171] Table 25 Synergistic coefficients of high-concentration imazalil compound groups

[0172]

[0173] As shown in Tables 24 and 25:

[0174] High-concentration single agent P500: The rot rate has been reduced to 6.7%, and the marketable fruit rate is 70.0%, indicating that high-concentration imazalil itself has strong anti-corrosion ability, but its improvement on scale yellowing is limited.

[0175] The low-concentration compound X50P125, compared to the high-concentration single agent P500, exhibits a lower yellowing index, a higher rate of marketable fruit, and requires only 1 / 4 the amount of prochloraz used in P500. This indicates that the addition of XYZ enables prochloraz to achieve "reduced dosage and increased efficacy."

[0176] High-concentration compound X50P500: Compared with X50P125, X50P500 showed slight improvement in yellowing index and decay rate, but the difference was not significant (p > 0.05); the synergy coefficients SR were 1.095 for yellowing and 1.113 for decay, both lower than 1.2, indicating that further increasing the concentration of imazalil could not produce a synergistic effect, but instead reduced the synergistic coefficient.

[0177] The combination of XYZ 50 mg / L + prochloraz 125 mg / L achieves or even exceeds the preservation effect of high-concentration prochloraz (500 mg / L) while reducing the amount of prochloraz used by 75%, which is in line with the green control concept of reducing pesticide use and increasing efficiency.

[0178] Taking into account the effects of maintaining green color, preventing decay, controlling weight loss, increasing the marketable fruit rate, and reducing pesticide use, prochloraz is the best fungicide choice for compounding with isooctyl chlorpyrifos. The optimal compounding scheme is XYZ 50 mg / L + prochloraz 125 mg / L.

[0179] In summary, this invention is the first to apply isooctyl clopyralid to the preservation of dragon fruit, demonstrating its ability to significantly delay the yellowing of dragon fruit scales. Furthermore, when combined with fungicides such as imazalil, it can synergistically achieve both green preservation and anti-corrosion functions, resulting in excellent overall preservation effects.

[0180] The above description is a detailed explanation of preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical concept presented in the present invention should fall within the patent scope covered by the present invention.

Claims

1. Application of isooctyl clopyralid in delaying yellowing of dragon fruit scales.

2. The application according to claim 1, characterized in that, The mass concentration of isooctyl chlorpyrifos is 25-100 mg / L.

3. A dragon fruit preservative, characterized in that, The preservative contains isooctyl clopyralid and a bactericide.

4. The dragon fruit preservative according to claim 3, characterized in that, The fungicide is selected from one or more of imazalil, pyraclostrobin, and thiamethoxam.

5. The dragon fruit preservative according to claim 4, characterized in that, The bactericide is imazalil, the mass concentration of isooctyl clopyralid is 25-100 mg / L, and the mass concentration of imazalil is 100-500 mg / L.

6. The dragon fruit preservative according to claim 5, characterized in that, The mass concentration of isooctyl clopyralid is 50 mg / L, and the mass concentration of imazalil is 125 mg / L.

7. A method for preserving dragon fruit using the preservative described in any one of claims 3-6, characterized in that, Includes the following steps: After harvesting, soak the dragon fruit in a diluted preservative solution for 1-5 minutes, then remove and air dry before packaging and storage.

8. The method according to claim 7, characterized in that, The soaking time is 2-3 minutes; the storage is at room temperature or refrigerated at low temperature.

9. The application of the dragon fruit preservative according to any one of claims 3-6 in simultaneously delaying the yellowing of dragon fruit scales and reducing the fruit decay rate.

10. Application of clopyralid isooctyl ester in enhancing the activity of prochloraz-induced defense enzymes in dragon fruit, wherein the defense enzymes include chitinase and β-1,3-glucanase.

Images