Improving Cold Stress Tolerance of Strawberry (Fragaria × Ananassa Cv. Paros) by Exogenous Melatonin

Strawberry (Fragaria× ananassa Duch.) is one of the most important berry crops worldwide. Frost damage during winter and chilling injuries in spring significantly reduce the yield and quality of sensitive and semi-sensitive strawberry cultivars. This study explored the potential of melatonin (N-acetyl-5-methoxytryptamine), a phytohormone known for its stress-alleviating properties, to mitigate cold stress in the semi-sensitive strawberry cultivar ‘Paros’. Strawberry plants were treated with 100μM melatonin for two weeks before exposure to cold stress (4 °C for 3 h). After the cold stress, several selected physiological and biochemical markers related to cold tolerance were analyzed in the leaves of melatonin-treated and control plants. Total chlorophyll content, carotenoids, proline, antioxidant capacity, melatonin, ABA, and IAA were 61.96%, 59.75%, 239.2%, 23.23%, 794.12%, 143.75%, and 78.26% higher in melatonin-treated plants, respectively, compared to control plants. Melatonin treatment had no significant effect on carbohydrate content, while glucose and fructose levels were markedly lower by 36.21 and 52.65% respectively in melatonin-treated plants, likely due to their conversion into compatible solutes or more complex compounds. These findings suggest that melatonin, as an effective phytohormone, has the potential to mitigate the negative effects of cold stress on strawberries and can be utilized as a promising strategy in managing cold stress to enhance the production and quality of this crop.