Impact of 24-epibrassinoliode and methyl jasmonate on quality of Red Delicious apples.

BACKGROUND: Changes in apple fruit quality indices in response to foliar spray with 24-epibrassinolide (EBL) at 0 and 1 µmol L-1 and methyl jasmonate (MeJA) at 0 and 0.5 µmol L-1 , as well as the combination of these phytohormones, were investigated at harvest and during cold storage. RESULTS: Both phytohormones synergistically enhanced the fruit firmness, specific weight, size, fresh weight, water content, total antioxidant activity, total phenolics, ascorbic acid, total anthocyanins, total soluble solids/titratable acidity ratio and precocity. In addition, the fruit abscission pattern was changed in response to different treatments. Treated fruit exhibited lower weight loss and internal breakdown symptoms and higher total soluble solids index, firmness and phytochemicals during cold storage. A negative correlation was seen between fruit mass, firmness, specific weight, antioxidant activity, total phenolics and vitamin C content with internal breakdown occurrence and weight loss. CONCLUSION: Foliar spray with EBL and MeJA during the growth season is a good environmental friendly and safe method for enhancing the apple fruit different quality parameters, marketability and postharvest life. © 2023 Society of Chemical Industry.

Investigation of pectolytic and PR genes expression, quality and phytochemical contents in organic and non-organic table grapes at harvest and during storage.

The demand for organic table grapes is increasing worldwide. However, comprehensive information of quality parameters and phytochemical compounds in organically grown fruit remain unclear. Furthermore, table grapes are perishable and postharvest quality retention and waste prevention is very important. In this study we have compared the differences between organic and non-organic table grapes in terms of phytochemical compounds and quality parameters as well as the changes in the expression levels of pathogen related and lytic genes during storage. Organic fruit showed higher levels of phenolics, flavonoids, caffeic acid, hydrogen peroxide, protein content, antioxidant and anti-stress enzymes and total antioxidant activities at harvest and during storage. Although, the expression levels of polygalactronases, pectin methyl esterase, chitinase and glucanase genes was lower in organically grown table grapes at harvest, but the expression of all these genes was significantly increased during cold storage. After 60 days of cold storage the expression levels of pectin methyl esterase, chitinase and glucanase genes was significantly higher than the conventionally grown grape berries in organic ones. The highest expression of polygalacturonase was recorded in organic samples after 30 days of storage. There was no significant difference between the two types of table grapes for decay extension and tissue deterioration rate. The results of this study indicate that due to higher levels of phytochemicals and antioxidant compounds the organic table grapes have a higher nutritional quality. Furthermore, the increase in PR and pectolytic genes expression levels is enough for decreasing the fruit susceptibility to decay pathogens and enhancing the postharvest life of organic grapes.

Exogenous methyl jasmonate enhances phytochemicals and delays senescence in harvested strawberries by modulating GABA shunt pathway.

In order to illustrate the relationship between methyl jasmonate (MeJA) and gamma aminobutyric acid (GABA) in maintaining the quality and improving the postharvest life of strawberry fruit, the harvested fruit were treated with MeJA for 16 h at 20 °C and stored at 3 ± 0.5 °C for 12 days. MeJA enhanced the expression levels of GABA shunt pathway-related genes, including glutamate decarboxylase, GABA transaminase, and succinic semialdehyde dehydrogenase, leading to an increase in GABA accumulation. Treated fruit showed higher levels of total acids, anthocyanins, total phenolics, antioxidants, and phenylalanine ammonia-lyase activity, and lower levels of cell membrane deterioration, total soluble solids, polyphenol oxidase activity and decay incidence rate. The results suggest that the positive effects of MeJA in extending the fruit postharvest life, enhancing phytochemical compounds, and decreasing the decay incidence rate may be due to the effects on motivating GABA shunt pathway and PAL enzyme activity.

24-Epibrasinolide Modulates the Vase Life of Lisianthus Cut Flowers by Modulating ACC Oxidase Enzyme Activity and Physiological Responses.

Ethylene is the most important factor playing roles in senescence and deterioration of harvested crops including cut flowers. Brassinosteroids (BRs), as natural phytohormones, have been reported to differently modulate ethylene production and related senescence processes in different crops. This study was carried out to determine the effects of different levels of 24-epibrassinolide (EBL) on ACC oxidase enzyme activity, the final enzyme in ethylene biosynthesis pathway, vase life, and senescence rate in lisianthus cut flowers. Harvested flowers were treated with EBL (at 0, 3, 6, and 9 µmol/L) and kept at 25 °C for 15 days. The ACC oxidase activity, water absorption, malondialdehyde (MDA) production and vase solution absorption rates, chlorophyll and anthocyanin contents, and the vase life of the flowers were evaluated during and at the end of storage. EBL at 3 µmol/L significantly (p ≤ 0.01) enhanced the flower vase life by decreasing the ACC oxidase activity, MDA production and senescence rates, and enhancing chlorophyll and anthocyanin biosynthesis and accumulation, relative water content, and vase solution absorption rates. By increasing the concentration, EBL negatively affected the flower vase life and postharvest quality probably via enhancing the ACC oxidase enzyme activity and subsequent ethylene production. EBL at 6 and 9 µmol/L and in a concentration dependent manner, enhanced the ACC oxidase activity and MDA production rate and decreased chlorophyll and anthocyanin accumulation and water absorption rate. The results indicate that the effects of brassinosteroids on ethylene production and physiology of lisianthus cut flowers is highly dose dependent.

Foliar application of ascorbic and citric acids enhanced 'Red Spur' apple fruit quality, bioactive compounds and antioxidant activity.

This study aimed to assess the effect of the foliar application of ascorbic acid (AA) and citric acid (CA) on total antioxidant activity (TAA), total phenolics, total flavonoids, total anthocyanin content, antioxidant enzymes, phenylalanine ammonialyase (PAL), and polyphenol oxidase (PPO) activities in apple 'Red Spur'. The experiment was conducted on 12-years-old trees 'Red Spur' grafted on MM106 rootstock. The trees were sprayed with AA (0, 200 and 400 mg L-1) and/or CA (0, 200 and 400 mg L-1) at three different times during summer. Foliar application with AA and CA significantly (p < 0.01) enhanced all measured quality attributes and decreased the activity of PPO. Fruit from trees treated with AA at 400 mg L-1 and CA at 200 mg L-1 showed the highest TAA and catalase (CAT) enzyme activity. Total phenolics increased in fruits when trees were sprayed with AA and CA. Contrasting, AA treatment, CA had no significant effect on guaiacol peroxidase (G-POD). A significant decrease in PPO activity was detected in fruits when treated with both AA and CA. Both treatments significantly decreased the activity of PAL at 400 mg L-1. Considering the results, foliar application of AA and CA, either alone or in combination improved the quality and nutraceutical properties of 'Red Spur' apple.

Methyl jasmonate effectively enhanced some defense enzymes activity and Total Antioxidant content in harvested "Sabrosa" strawberry fruit.

The use of chemicals in postharvest technology of horticultural crops is highly restricted and it is necessary to introduce safe food preserving methods. Strawberry is very susceptible to postharvest losses and more than 50% of harvested fruit is lost in Iran. Effect of postharvest treatment with methyl jasmonate (at 0, 8, and 16 µmol L(-1)) on some quality attributes of Sabrosa strawberry fruit during storage at 1 ± 0.5°C with 90-95% RH for 14 days followed by 24 h at 20°C was studied. Methyl jasmonate, at both concentrations, decreased weight loss and retained marketability of fruits. Catalase activity of treated fruits was decreased during the first days, but showed a substantial increase during the second week. Methyl jasmonate, in a concentration-dependent manner, enhanced peroxidase activity. Fruit total antioxidant capacity was enhanced by methyl jasmonate treatment. The results indicated that methyl jasmonate plays a key role in establishing resistance against stresses, enhancing fruit defense systems, antioxidant capacity, and storage life leading to decreased postharvest losses. This phytochemical has a good potential to be used in postharvest technology of Sabrosa strawberry fruit and enhance the fruit postharvest life.

Alleviation of postharvest chilling injury of tomato fruit by salicylic acid treatment.

Tomato fruit at the mature green stage were treated with salicylic acid at different concentration (0, 1 and 2 mM) and analyzed for chilling injury (CI), electrolyte leakage (EL), malondialdehyde (MDA) and proline contents and phospholipase D (PLD) and lipoxygenase (LOX) activities during cold storage. PLD and LOX activities were significantly reduced by salicylic acid treatment. Compared with the control fruit, salicylic acid treatment alleviated chilling injury, reduced electrolyte leakage, malondialdehyde content and increased proline content. Our result suggest that the reduce activity of PLD and LOX, by salicylic acid may be a chilling tolerance strategy in tomato fruit. Inhibition of PLD and LOX activity during low temperature storage could ameliorate chilling injury and oxidation damage and enhance membrane integrity in tomato fruit.