Calcium Chloride Enhances Defense Response Against Diaporthe nobilis by Eliciting Reactive Oxygen Species in Kiwifruit

Abstract

Kiwifruit (Actinidia spp.) rot, caused by pathogenic fungi, represents the most severe disease during postharvest storage. The utilization of induced resistance against fungal pathogens in harvested fruit has been demonstrated as a promising strategy for controlling postharvest losses. In this study, the effect of calcium chloride (CaCl₂) on induction of resistance to Diaporthe nobilis, one of the most epidemic pathogens of soft rot in kiwifruit, and the underlying mechanisms were investigated. Our data showed that the application of 3% CaCl₂ resulted in smaller rotten lesion diameters after inoculation with the pathogen, induced expression of the respiratory burst oxidase homolog (RBOH) gene family, and increased accumulation of reactive oxygen species (ROS). Moreover, we found that the activity of three pathogenesis-related antioxidant enzymes—peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD)—as well as the expression of important defense-related genes, was enhanced by CaCl₂ treatment. The results of our study suggest that the application of CaCl₂ treatment holds promise as a green and viable method for effectively preventing and safeguarding kiwifruit against postharvest decay.