Ferulic acid enhanced resistance against blue mold of Malus domestica by regulating reactive oxygen species and phenylpropanoid metabolism

Abstract

Postharvest decay of fruit caused by phytopathogen often causes tremendous losses during logistics. Ferulic acid is a kind of phenolic acid which has potential antimicrobial ability and initiates defense responses. This study performed to evaluate the induced resistance of ferulic acid against blue mold of apples (cv. Qiujin) as well as the mechanism involved in its action. Results suggested that 1.0 g L−1 ferulic acid remarkably reduced lesion diameter of Penicillium expansum-inoculated apples and colony diameter in vitro. The activities and gene expressions of catalase, superoxide dismutase, peroxidase, dehydroascorbate reductase, glutathione reductase, monodehydroascorbate reductase, ascorbate peroxidase, and nicotinamide adenine dinucleotide phosphate oxidase were distinctly improved by ferulic acid immersion. Ferulic acid also promoted ascorbic acid and reduced glutathione contents, whereas decreased hydrogen peroxide and malondialdehyde contents in apples. Moreover, ferulic acid enhanced the gene expressions and activities of cinnamyl alcohol dehydrogenase, 4-coumarate coenzyme A ligase, cinnamate-4-hydroxylase, and phenylalanine ammonia-lyase, resulting in caffeic acid, flavonoids, lignin, total phenolics, and p-coumaric acid accumulation in apples. Taken together, ferulic acid could activate the activities and gene expressions of the key enzymes in phenylpropanoid pathway as well as reactive oxygen species metabolism to promote the synthesis of antioxidants and secondary metabolites, thereby increasing disease resistance of apples.