Low-temperature conditioning induces chilling tolerance in 'Hayward' kiwifruit by enhancing antioxidant enzyme activity and regulating en-dogenous hormones levels

BACKGROUNDTo understand the mechanisms leading to the enhanced chilling tolerance of kiwifruit by low-temperature conditioning (LTC, 12 degrees C for 3 days), this study investigated the effect of LTC on chilling tolerance and changes in antioxidant enzyme activities and endogenous hormones. RESULTSLTC significantly alleviated chilling injury in kiwifruit. Fruits treated with LTC maintained lower respiration and ethylene production and higher firmness. Furthermore, this treatment inhibited the accumulation of malondialdehyde, superoxide radicals and hydrogen peroxide and the increase in membrane permeability and increased the activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase under chilling stress. The treatment also maintained higher levels of endogenous abscisic acid (ABA), indole-3-acetic acid (IAA) and zeatin riboside (ZR), lower gibberellic acid (GA(3)) levels and higher ABA/GA(3) and ABA/IAA ratios. CONCLUSIONThe results suggested that LTC alleviated chilling injury in kiwifruit by improving antioxidant enzyme activities and maintaining higher levels of endogenous ABA, IAA and ZR, lower GA(3) levels and higher ABA/GA(3) and ABA/IAA ratios. (c) 2013 Society of Chemical Industry