effect of pre-harvest application of polyamines on quality and shelf life of kiwifruit cv. hayward

softening and microbial activity are the most common problems of kiwifruit during storage. in order to improve these problems, pre- harvest treatments of putrescine and spermidine were studied on shelf life of kiwifruit cv. hayward. foliar spraying of different concentrations of purescine (0, 1 and 2 mm) and spermidine (0, 1 and 2 mm) has been done at 40 and 20 days before harvest. different characteristics were analyzed at 0 (before storage), 11 and 14 weeks after storage. fruits were harvested at commercial maturity (tss= 6.2 brix) and stored at 1.5±1 0c and 90±5% relative humidity for 14 weeks. results showed that the highest fruit firmness (3.09 kg) corresponded to concentration of 2 mm of putrescine and spermidine and the lowest value was observed (2.16 kg) in control. the lowest amount of microbial activity, malondialdehyde and weight loss was related to treated fruits. antioxidant activity, phenolic compound and total chlorophyll were affected by the treatments and highest value belonged to different levels of putrescine and spermidine. polyamine treatments delayed changes of various color indices, vitamin c, total soluble solids, total acid and ph. in general, the exogenous putrescine and spermidine delayed softening and reduced microbial activity during storage.