Abstract: Chlorogenic acid is the most predominant phenolic compound in apple fruit. This study demonstrated chlorogenic acid to be able to inhibit the growth of Botrytis cinerea in vitro when used at a concentration of 300 μg/mL. ‘Fuji’ apples were dipped in chlorogenic acid solution at this concentration for 30 min, wounded and inoculated with Botrytis cinerea after 24 h. Distilled water treatment was used as a control. Relevant metabolic enzyme activities and the contents of total phenols, flavonoids and lignin in the fruit samples were measured. The results showed that 300 μg/mL chlorogenic acid treatment significantly reduced the incidence of gray mold disease on apple fruit and suppressed the expansion of lesion diameter (P < 0.05). This treatment increased the activity of chitinase and β-1,3-glucanase, induced the response of the enzymes involved in the phenolic metabolism pathway as manifested by significantly increased activities of phenylalanine ammonia lyase, cinnamic acid 4-hydroxylase and 4-coumalyl CoA ligase (P < 0.05), and promoted the accumulation of total phenols, flavonoids and lignin, thereby delaying the development of gray mold disease. This study provides theoretical references for the application of chlorogenic acid in the prevention of gray mold disease on apple fruit.

Key words: apple; chlorogenic acid; induced resistance; gray mold; defensive enzyme activity