Karrikins Regulate the Redox Balance and Sugar Metabolism of Postharvest Kiwifruit (Actinidia deliciosa)

Karrikins, a class of butenolide compounds derived from plant-derived smoke, positively regulate plant development and stress tolerance. However, their effects on postharvest fruit have scarcely been reported. In this study, karrikin solution was prepared by absorbing maize straw smoke into water, and kiwifruits (<i>Actinidia deliciosa</i>) were immersed in different concentrations of this solution to determine the optimal concentration based on respiratory rate, relative conductivity, firmness, soluble solids content, and appearance of the kiwifruits. Subsequently, the regulation of reactive oxygen species (ROS) and soluble sugars metabolism by karrikins were studied. The results showed that the optimal dose of karrikins for kiwifruit was 1.20 μmol L^-1. Karrikins enhanced the activities of superoxide dismutase, catalase, enzymes in the ascorbate-glutathione pathway, and soluble sugars metabolism, increased the concentrations of reducing ascorbate, glutathione, sucrose, and fructose-6-phosphate, suppressed ROS concentrations, and maintained the quality of kiwifruit during storage. These results suggest that karrikins could be a potential tool to modulate fruit ripening, with their effects depending on the dosage used.