Controlling effect and mechanism of burdock fructooligosaccharide against Alternaria fruit rot in blueberry during postharvest

Burdock fructooligosaccharide (BFO), a naturally occurring elicitor derived from the roots of Arctium lappa, can promote postharvest disease resistance in grapes, apples, bananas, and so forth. However, its controlling effect and mechanism against postharvest diseases caused by Alternaria tenuissima in blueberries are unclear. This study showed that BFO treatment restrained the postharvest development of Alternaria fruit rot in blueberries. In the initial stage of fruit storage, BFO treatment induced a hydrogen peroxide burst promoting the blueberry resistance response against A. tenuissima invasion. In addition, BFO treatment increased the activities and gene expression of antioxidant enzymes and pathogenesis-related proteins, such as superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, chitinase, and β-1,3-glucanase, thereby enhancing the fruit resistance to pathogens. The increased activities and gene expression of phenylalanine ammonia-lyase, 4-coumarate CoA ligase, and cinnamate 4-hydroxylase in blueberries were accompanied by increased levels of total phenolics, flavonoids, anthocyanin, and lignin, indicating the activation of the phenylpropanoid pathway. In conclusion, BFO can be a promising elicitor to control the Alternaria fruit rot in blueberries.