JIA-2019-11

2519 Maratab Ali et al. Journal of Integrative Agriculture 2019, 18(11): 2514–2520 together our work identified that pre-harvest OA treatment apparently improved fruit quality of kiwifruit during storage. Generally, final AsA level in kiwifruit during postharvest attributes to it’s biosynthesis, catabolism, and recycling (Jiang et al . 2018). Oxalic acid and tartaric acid are the main metabolites of AsA catabolism in fruit. Also, our work observed higher tartaric acid content rather than oxalic acid content in kiwifruit with pre-harvest OA treatment during the early period of storage. Further investigations need to be addressed the effects of pre-harvest OA treatment on AsA metabolism including the de novo biosynthesis, degradation and recycling to increase AsA level in kiwifruit during development stage and postharvest. In ethanol fermentation metabolism, higher activities of PDC and ADH result in over accumulation of acetaldehyde and ethanol in relation to off-flavor development in fruit during storage (Shi et al . 2007; Tietel et al . 2011; Botondi et al . 2012). Also, our previous work has reported that, compared to room temperature, low temperature limits the accumulation of ethanol and acetaldehyde in kiwifruit cv . Bruno during the period of storage, which is primarily attributed to decreases in the activities of PDC and ADH, as well as their encoded genes expression (Li et al . 2016). In our present study, pre-harvest OA treatment proved itself as quality enhancer strategy, since it reduced the activities of PDC and ADH enzymes and inhibited the exceeded accumulation level of ethanol fermentation metabolites, particularly for inhibiting the ethanol accumulation in kiwifruit during later period of storage. Meanwhile, our data showed that the differences on acetaldehyde and ethanol content between fruit from the control and OA treatment were higher than those in PDC and ADH activities. Similarly, the activities of PDC and ADH in bell pepper fruit increase at low O 2 , especially at 1% O 2 , but their activities do not correlate with acetaldehyde and ethanol accumulation in the fruit stored in 0% O 2 , which indicate that the low O 2 levels play a major role in increasing concentrations of ethanolic fermentation cofactors and substrates, thereby determine ethanolic flux (Imahori et al . 2002). Thus, besides PDC and ADH, further work about the pre-harvest OA treatment in controlling the ethanol accumulation in kiwifruit need to be addressed. Moreover, previously different investigations have reported the positive impact of pre-harvest OA treatment on significant increases in potential antioxidants, bioactive compounds and phytochemical contents in a number of horticultural crops, such as peach, sweet cherry, artichoke and coriander (Wurms et al . 2010; Martínez-Esplá et al . 2014, 2017; Razavi and Hajilou 2016; El-Zaeddi et al . 2017). Therefore, pre-harvest spraying of OA might be a worthwhile strategy for some selected horticultural crops in relation to improvement of quality during postharvest. 5. Conclusion Pre-harvest spraying of OA increased the contents of AsA and T-AsA accompanied with higher AsA/DHA ratio, and reduced activities of PDC and ADH to regulate less accumulation of acetaldehyde and ethanol in kiwifruit cv . Bruno during storage at room temperature, which collectively contributed in improving the fruit quality during postharvest. Acknowledgements The authors acknowledge the financial support provided by the National Natural Science Foundation of China (31671908), and the National Key Research and Development Program of China (2016YFD0400901). References Botondi R, Russo V, Mencarelli F. 2012. Anaerobic metabolism during short and long term storage of kiwifruit. Postharvest Biology and Technolog y, 64 , 83–90. Garcia C V, Quek S Y, Stevenson R J, Winz R A. 2012. Characterisation of bound volatile compounds of a low flavour kiwifruit species: Actinidia eriantha . Food Chemistry , 134 , 655–661. Imahori Y, Kota M, Ueda Y, Ishimaru M, Cachin K. 2002. Regulation of ethanolic fermentation in bell pepper fruit under low oxygen stress. Postharvest Biology and Technology , 25 , 159–167. Jiang Z Y, Zhong Y, Zheng J, Ali M, Liu G D, Zheng X L. 2018. L-ascorbic acid metabolism in an ascorbate-rich kiwifruit ( Actinidia . Eriantha Benth.) cv. ‘White’ during postharvest. Plant Physiology and Biochemistry , 124 , 20–28. 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