Effect of hot water treatments on chilling injury and expression of a new C-repeat binding factor (CBF) in ‘Hongyang’ kiwifruit during low temperature storage

Abstract

Kiwifruit is cold-sensitive and very susceptible to chilling injury (CI) during low temperature storage. In this study, kiwifruit (Actinidia chinensis cv. Hongyang) were pre-treated by water dip for 10min at 20 (control) or 35, 45, or 55°C (heat pretreatments) and then stored at 0°C for 90 days to investigate the effect of hot water treatments (HWT) on chilling injury tolerance. Results showed that 35°C and 45°C HWT alleviated but did not completely prevent chilling injury development. By contrast, 55°C HWT increased symptoms of chilling injury. The 45°C HWT was the most effective at reducing chilling injury index and incidence. Compared with the other HWT, fruit treated at 45°C exhibited higher firmness and soluble solids content (SSC), and lower malondialdehyde (MDA) content, lipoxygenase (LOX) activity and ethylene production rate. C-repeat/dehydration-responsive element binding factors (CBFs) are key regulators in cold response. To investigate the molecular regulation of HWT on chilling tolerance of kiwifruit, a 637bp CBF gene was identified and the relative expression of AcCBF was measured by RT-qPCR. In accordance with the effects of HWT on physiological parameters of chilling injury, AcCBF expression level was highest in the 45°C HWT. These results indicate that HWT at 45°C for 10min prior to low temperature storage is effective for alleviating symptoms of chilling injury in ‘Hongyang’ kiwifruit.