Post-harvest curing treatment maintains the quality of sweetpotato storage roots by regulating reactive oxygen species homeostasis and nitric oxide metabolism

Abstract

Sweetpotato (Ipomoea batatas L. Lam) is an economically important crop whose storage roots are used as a nutrient source and in processed foods, livestock feed, and pigments. Post-harvest handling may cause wounding to storage roots, which makes them susceptible to infection by pathogenic microorganisms, which directly affects quality and marketability. Microbial spoilage in stored roots is commonly controlled by curing, a temperature treatment that promotes wound healing through molecular biochemical mechanisms that are not well understood. To investigate these mechanisms, changes in reactive oxygen species (ROS) and nitric oxide (NO) metabolism were investigated in sweetpotato storage roots. Storage roots were cured at 33 degrees C or 13 degrees C (uncured controls) for 3 days, and their physiological characteristics were examined after 56 days. Cured roots did not show significant changes after 56 days, while control roots showed characteristic damage due to wounds becoming infected with pathogens. Changes in H2O2 and NO2- levels were observed in cured roots after 3 days; by contrast, changes in control roots were seen at 28 and 56 days. RBOHC, CuAO1, and PAO2 expression, and SOD activity, which are all involved in H2O2 production, were high during the early curing stage, whereas levels of nitrate reductase, which is involved in NO2- production, were low. Transcriptomic analysis confirmed that expression of genes related to ROS and NO metabolism altered during the early stage of curing. This study provides valuable insight into the role played by ROS and NO metabolism in curing-mediated wound healing in stored sweetpotato roots.