Effect Of Preharvest GA₃ Sparys Combined With Postharvest MAP, IW On Chilling Injury And Fruit Quality Of Plums

The plum fruit is sensesive to chilling injury during low temperature storage. The surface of the fruit appears spots, pulp browning and quality breakdown. In this study, plums (cv. Ruby) were preharvest sprayed with GA3 at 100ppm at three periods (a week before fruit expanding stage, fruit expanding stage, a week after fruit expanding stage) single or combination. After harvest the treated fruit were packed with PE film (0.04mm) and intermittent warming (IW) every 14days during 0℃storage, to research effect of preharvest GA3 treatment on chilling injury and partial mechanism. The results indicated as below:1. The treatments significantly decreased CI index and BI of plums, Compared with the control, the optimum treatment for GA3 was sprayed for 3 times at a week before fruit expanding stage, fruit expanding stage and a week after fruit expanding stage.2. The treatments decreased the content of H2O2 and O2- and maintain membrane permeability, reduced the malondialdehyde (MDA) content, increased the activity of superoxide dismutase (SOD) and catalase (CAT),decreased the activity of peroxidase (POD) and polyphenoloxidase(PPO).3. The treatments decreased the activity of phenylalanine ammonia-lyase (PAL) and 4-coumarate:CoA ligase(4CL), reduced total phenols (TP), flavonoid and ligin content. Phenolic compounds were determined lower in treated fruit by HPLC.4. The treatments had effect on the quality of plum, maintained the firmness and soluble solids content (SSC), delayed decrease of titratable acidity (TA) and ascorbic acid (ASA) content.It is suggested that preharvest GA3 spray combined with postharvest MAP and IW significantly reduced CI of plum during low temperature storage by inhibite phenylpropanoid pathway, enhance the activity of antioxidation enzymes.