Modulating physico-chemical profile and post-harvest quality of mango cv. Kesar through foliar application of novel plant growth regulators under HDP

Introduction

Mango (Mangifera indica L.) is one of the most vital fruit crops in Asia deeply rooted in Indian culture and tradition since ancient times (Bose et al., 2001) [6] . It's presence in early sanskrit literature under the name Amra highlights its long-standing heritage. From the historical praises of Babur to its status as the national fruit of India mango stands as a timeless symbol of country's heritage. Mango has earned the undisputed title of the king of fruits due to its unparalleled flavor, fragrance and nutritional richness. Mangifera indica is characterized by an exceptionally dense nutrient matrix. Quantitatively a 100 g portion of mango pulp is primarily an aqueous carbohydrate system containing 81.7% water and 16%. carbohydrates complemented by specific concentrations of dietary fiber, lipids and proteins. The fruit's micronutrient density is particularly distinguished by its high Vitamin A content (approximately 4,800 IU) alongside a robust profile of Vitamin C, Vitamin B-complex and essential minerals including iron, phosphorus and magnesium. Furthermore, its biological efficacy is significantly bolstered by a diverse array of secondary metabolites and antioxidants (Joyce et al., 2014) [8] . The physiological benefits of the mango extend to cardiovascular optimization. High concentrations of potassium and magnesium facilitate blood pressure regulation and rhythmic stability, while the presence of the xanthone glycoside, mangiferin offers potential anti-inflammatory protection for cardiac tissues (Abdalla et al., 2007) [1] . Mango (Mangifera indica) is distinguished by its exceptional flavour profile and aromatic intensity offering significant utility at every phase of its physiological development. The immature fruit is primarily utilized for the production of chutneys and pickles, whereas the ripe fruit serves as both a premium dessert and a raw material for industrial products like nectar, jam and squashes. Beyond the pulp the mango seed kernel contains high-quality fats, making it a valuable resource for saponification and a functional substitute for cocoa butter in the confectionery industry.

Materials and Methods

The research entitled "Modulating physico-chemical profile and post-harvest quality of mango cv. kesar through foliar application of novel plant growth regulators under HDP" conducted at Fruit Research Station, Sakkarbaug, College of Horticulture, JAU, Junagadh during the year 2023-24 and 2024-25. The experimental design selected was Randomized Block Design consisting of ten treatments comprising T 1 (Control), T 2 (Tricontanol 500 ppm), T 3 (Tricontanol 750 ppm), T 4 (Tricontanol 1000 ppm), T 5 (Brassinosteroid 1ppm), T 6 (Brassinosteroid 2 ppm), T 7 (Brassinosteroid 3 ppm), T 8 (Salicylic acid 1500 ppm), T 9 (Salicylic acid 2000 ppm) and T 10 (Salicylic acid 2500 ppm) which were replicated three times. The primary goal of this investigation was to evaluate the influence of contemporary plant growth regulators on the qualitative traits of mango. Key quality indices, including Total Soluble Solids (TSS), Vitamin A, fruit firmness, ascorbic acid content, and titratable acidity, along with sugar fractions (reducing, non-reducing, and total sugars) and shelf life, were rigorously monitored. The experimental data were subjected to statistical validation following the methodology of Panse and Sukhatme (1985) [11] . Treatment effects were scrutinized using the 'F' test, while the Standard Error of Mean (S.Em.±) and Critical Difference (CD) at a 5% probability level were utilized to determine the significance of variations across different treatments. Following methodology and formulas used to determine the quality parameters.

TSS ( o Brix)

Total Soluble Solids (TSS) was determined using a digital hand refractometer (with an accuracy of±0.2% Brix). The instrument was initially calibrated with distilled water to ensure precision. A drop of extracted mango pulp was placed on the prism and the resulting values were recorded in degrees Brix (°Brix). For each treatment five independent readings were documented and subsequently averaged to obtain a representative value.

The estimation of Vitamin A (as beta carotene) was carried out following the spectrophotometric method as described by Srivastava and Kumar (2005). A 5 g portion of the fresh sample was extracted with 10-15 ml of acetone and anhydrous sodium sulphate was added to ensure the removal of moisture. After decanting and repeating the process for complete extraction the supernatant was transferred to a separatory funnel. Following the addition of 10-15 ml of petroleum ether and thorough mixing the upper organic layer was collected and diluted to a final volume of 100 ml. The absorbance was measured at 452 nm and the beta carotene content was calculated using the standard formula.

β-Carotene (µg/100 g) = O.D. × 13.9 × 10 4 × 100 Sample weight (g) × 560 × 100 Vitamin A (µg/100 g) = β-Carotene (µg/100 g) 0.6

The ascorbic acid content in the fruit pulp was determined using the 2, 6-dichlorophenol indophenol visual titration method as suggested by Ranganna (1986) [13] . A 10 g representative pulp sample was homogenized and diluted to 100 ml using 3% metaphosphoric acid as a stabilizing medium. The suspension was allowed to stand for 30 minutes before being filtered through Whatman No. 1 filter paper. Prior to the analysis, the dye solution was standardized against a known concentration of synthetic ascorbic acid to establish the dye factor. A 5 ml aliquot of the filtered extract was titrated against the standardized dye until a persistent light pink endpoint was achieved for at least 15 seconds. The final vitamin C concentration was calculated based on the titration volume and expressed as mg per 100 g of pulp. Ascorbic acid content was calculated by using following equation.

Ascorbic acid (mg/100 g) = Titrate × Dye factor × volume made up × 100 Aliquot taken for estimation × Weight or volume of sample taken for estimation

Titratable acidity was determined following the standard A.O.A.C. (1970) procedure. A 5 g aliquot of fruit pulp was macerated with distilled water and filtered through a muslin cloth to obtain a clear extract. This extract was titrated against 0.1 N NaOH solution utilizing phenolphthalein as a visual indicator. The persistence of a light pink color was recorded as the equivalence point. Finally, the acidity was calculated and expressed as a percentage of citric acid equivalent using the following formula:

Titrate × Normality of NaOH × Equivalent wt. of citric acid × 100 Weight of sample (5 g) × 1000

Reducing sugar content was estimated using the dinitrosalicylic acid (DNSA) method as prescribed by Sadasivam and Manickam (1999) [15] . A 0.1 g sample was thoroughly crushed and extracted with 10 ml of 80% methanol. Subsequently a 0.1 ml aliquot of the supernatant was diluted with 0.9 ml of distilled water to reach a final volume of 1.0 ml. Following this 3.0 ml of DNS reagent was added to each test tube and mixed thoroughly. The reaction mixture was incubated in a boiling water bath for 10-15 minutes until the color developed then cooled to ambient temperature. The absorbance was measured at 565 nm using a spectrophotometer and the concentration was determined using the following formula:

Reducing sugar (%) = O.D. × G.F. × 100 × Total volume × 100 Sample weight × Aliquot taken

Non-reducing sugar content was derived by calculating the difference between total sugars and reducing sugars for each pulp sample. The resulting values were expressed as a percentage on a fresh weight basis. Non-reducing Sugar (%) = Total sugar (%)-Reducing sugar (%) 2.7 Total sugars (%) Take 0.1 g sample of mango pulp and mixed and crushed with 10 ml of 2.5 N 80% methanol. Then 0.1 ml aliquot from crushed sample was taken and added 0.9 ml distilled water to make final volume of 1.0 ml. Then 1.0 ml phenol 5% and 5.0 ml of 96% H 2 SO 4 were added one by one in each test tube. Then all samples were put in ice bath for 10-15 minutes. Spectrophotometer reading was taken at 490 nm wavelength (Rangana, 1986) [13] . By use of the following formula total sugar content was calculated: Fruit firmness was measured by means of penetrometer. The circular thin size of skin about 1 cm diameter was removed from the fruit surface with the help of a sharp knife and the penetrometer adjusted to zero was pierced into the fruit up to the knob. The pressure required to penetrate flesh penetrometer was recorded in kg/cm 2 provided on the circular disk of the penetrometer. Firmness was measured on two opposite sides of a fruit and average values were worked out.

Shelf life was determined by monitoring five representative fruits per treatment under ambient storage conditions. The duration (in days) from the date of harvest to the stage where the fruits reached optimum edibility or showed the first signs of senescence (decay) was recorded. This period was defined as the total marketable lifespan of the fruit.

Results and Discussion

The quality parameters were found to be significantly influenced by different chemicals during both experimental years as well as in pooled result. The maximum value of non-reducing sugar of fruit (11.05 and 10.58%) was achieved when the plants were treated with brassinosteroid 1 ppm (T 5 ) during both individual experimental years, respectively. Furthermore, the pooled analysis also confirmed a significantly higher non-reducing sugar content (10.82%) in the same treatment. The maximum total sugar (16.45 and 15.85%) was registered with treatment brassinosteroid 1 ppm (T 5 ) during individual years, respectively. The pooled analysis further confirmed a significantly higher total sugar (16.15%) in the same treatment. The lowest acidity (0.209, 0.212 and 0.211%) was registered under the foliar application of brassinosteroid 1 ppm (T 5 ) during both experimental years as well as in pooled data, respectively. However, the control treatment (T 1 ) recorded lower values for all the above fruit quality attributing characters during the years 2023-24, 2024-25 and in the pooled data analysis.

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NS

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NS

The significant increase in TSS (total soluble solids) content following brassinosteroid application is primarily due to the enhanced source to sink mobilization of photo assimilates. brassinosteroid act as powerful signaling molecules that stimulate the activity of sucrose metabolizing enzymes such as invertases and sucrose synthase, which facilitate the unloading of sugars from the phloem into the fruit mesocarp. This result is in close conformity with the findings of Ramani et al. (2016) [12] , Almutairi et al. (2023) [2] , Balachandran et al. (2024) [4] and Hassan et al. (2025) [7] in mango. The increase in vitamin A is due to the brassinosteroid mediated upregulation of the carotenoid biosynthetic pathway, specifically activating the enzyme phytoene synthase (PSY). Brassinosteroid also promote the development of chromoplasts, which serve as storage units for beta carotene in the pulp. This leads to higher nutritional density and deeper pulp color. These findings align with previous studies of Balachandran et al. (2024) [4] and Sattar et al. (2024) [16] in mango.

The enhancement in ascorbic acid content is attributed to the brassinosteroid mediated upregulation of the L-galactose pathway, which increases the net biosynthesis of Vitamin C. Brassinosteroid reduce titratable acidity is primarily attributed to the accelerated metabolic utilization of organic acids as respiratory substrates. Brassinosteroid function as signaling molecules that fast track the fruit ripening process, leading to the rapid conversion of organic acids (mainly citric and malic acids) into sugars or their oxidation during respiration. These findings are in close conformity with the physiological observations of Roghabadi and Pakkish (2014) [14] in sweet cherry, Zhu et al. (2015) [18] in mandarin and Aly et al. (2021) [3] in sugar apple. The significant increase in sugar content following brassinosteroid application is primarily attributed to the accelerated hydrolysis of starch into simpler sugars. Brassinosteroid enhance the activity of key enzymes involved in carbohydrate metabolism such as alpha-amylase and beta-amylase which break down stored starch into glucose and fructose during fruit ripening. Furthermore, brassinosteroid promote the translocation of hexoses from the leaves to the fruit by increasing the sink strength of the mesocarp. The higher photosynthetic efficiency also ensures a continuous supply of precursors for sugar biosynthesis, ultimately resulting in an improved flavor profile. These results are in close conformity with the findings of Mostafa and Kotb (2018) [10] and Aly et al. (2021) [3] in sugar apple and Balachandran et al. (2024) [4] in mango. Brassinosteroid extend shelf life might be due to the delayed senescence and regulation of the respiration rate. Brassinosteroid help in maintaining the structural integrity of the fruit by inhibiting the enzymes responsible for cell wall degradation, such as pectinmethylesterase (PME) and polygalacturonase (PG). Consequently, the treated fruits retain their firmness and freshness for a longer duration, is in close conformity with the result of Ban et al. (2024) [5] in jujuba, Roghabadi and Pakkish (2014) [14] in sweet cherry and Meena et al. (2023) [9] in mango.

Conclusion

Based on the results obtained from the present experiment it can be concluded that the foliar spray of brassinosteroid 1 ppm at flowering, pea and marble stage improve quality parameters in mango cv. Kesar under HDP.

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