Fruit production is becoming increasingly difficult due to climate change and the cuts in recruitment of effective chemical products for protecting plants against pests and environmental factors. In this doctoral dissertation, we focused on the study of the effects of salicylic acid (SA) and its derivatives (acetylsalicylic acid (ASA) and 3-methylsalicylic acid (MeSA)) on the physico-chemical quality parameters of fruit and the response to infection by the fungus Monilinia laxa, one of the main causes of rotting of pome and stone fruit during storage. The results showed that salicylates affected the physico-chemical properties of fruit, with the effects varying according to the fruit species. Salicylate treatments improved colour and anthocyanin content in strawberries and peaches, while in apple they resulted in poorer red colour and lower yield of first quality at the expense of poorer colour. MeSA had a greater effect on the activity of phenylpropanoid pathway enzymes, resulting in higher levels of phenolic compounds such as flavonols and hydroxycinnamic acids and lower levels of anthocyanins. Salicylates also had a significant effect on inhibiting M. laxa infection, with curative use being more successful than preventive use. Soaking the fruit in MeSA solution after harvest reduced the spread of infection and the rapid growth of lesions. The results of this thesis open up the possibility of using salicylates, particularly MeSA, as environmentally friendly compounds for protection against fungal diseases and for use as compounds to improve crop quality, with direct potential benefits for fruit growers.
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