The use of preharvest and postharvest treatments with salicylic acid to control brown rot and the response to its infection with the synthesis of phenolic compounds in peach fruit

The effects of preharvest or/and postharvest treatments with salicylic acid (SA) on the physicochemical quality of peach fruit, infection with the fungus Monilinia laxa and the phenolic response to infection in SA treatments in different peach peel tissues were evaluated. Preharvest SA treatments had an effect on the physical quality parameters only at harvest on three times SA-sprayed peaches, with which a lower hue angle and a higher percentage of red blush occurred, indicating better coloration of the fruit. It was found that the intensity of M. laxa infection was not affected by preharvest SA treatments, only by soaking peach fruit in SA solution after harvest. On SA soaked peach fruit, M. laxa spread between 1.8 and 3.9 mm/day slower than on non-soaked fruit, resulting in a 34% lower intensity of infection five days after infection. Peach fruit treated with SA after harvest also had a significantly lower percentage of sporulating fruit (7.8%) compared to non-soaked fruit (68.9%). The phenolic response differed between tissues, since the proportion of hydroxycinnamic acids and anthocyanins was higher in the healthy tissue of infected fruit, while the proportion of flavanols was higher in the boundary tissue of infected fruit. The strongest phenolic response to infection and treatments with SA was in higher levels of neochlorogenic acid, cyanidin-3-glucosides and cyanidin-3-rutinosides.