Physiological and biochemical mechanisms regulating chilling tolerance in fruits and vegetables under postharvest salicylates and jasmonates treatments

Low temperature storage has been the main strategy to increase the shelf life of fruits and vegetables by reducing the rate of respiration and minimizing fungal disease growth. However, tropical and subtropical fruits and vegetables stored below 10-12 degrees C develop chilling injury (CI) following storage beyond the CI threshold. CI as a physiological disorder greatly reduces fruits and vegetables quality and frequently renders the product not saleable. The increasing demand for consumption of fresh fruits and vegetables, along with restriction on the use of synthetic chemicals to reduce CI, has encouraged scientific research to develop new technologies based on natural product such as salicylates and jasmonates. Membrane damage and reactive oxygen species (ROS) production are multifarious adverse effects of chilling as oxidative stress in sensitive fruits and vegetables. Chilling alleviating in fruits and vegetables treated with salicylates and jasmonates could be attributed to (I) Enhancing membrane integrity by reducing phospholipase D and C (PLD and PLC) and lipoxygenase (LOX) enzymes activities, enhancing unsaturated fatty acids/saturated fatty acids (unSFA/SFA) ratio probably through increase of fatty acid desaturases (FAD) gene expression and maintaining energy status, ATP and adenylate energy charge (AEC). (2) Enhancing heat shock proteins (HSPs) gene expression and accumulation. (3) Enhancing antioxidant system activity. (4) Enhancing arginine pathways which led to accumulation of signaling molecules with pivotal roles in improving chilling tolerance such as polyamines, nitric oxide, proline and gamma-aminobutyric acid (GABA). (5) Activation of C-repeat binding factor (CBF) pathway and (6) alteration in phenylalanine ammonialyase (PAL) and polyphenol oxidase (PPO) enzymes activities. In the present review, we have focused on impacts of exogenous salicylates and jasmonates treatments on postharvest chilling tolerance and mechanisms employed by these safe signaling molecules in fruits, vegetables and cut flowers have also been discussed. (C) 2013 Elsevier B.V. All rights reserved.