Brassinosteroids enhance the tolerance, production, and fruit quality of covered table grape vines

Plastic covering (PC) is used to speed up the ripening and harvesting of grapes while also shielding grapevines from unfavourable climatic conditions. This study aimed to determine how PC induced abiotic stress on covered vines and assess the role of brassinosteroids (Brs) in alleviating these impacts. The results showed that PC caused a substantial rise in soluble sugar, MDA, proline, total phenol, and antioxidant enzymes (catalase and ascorbate peroxidase) and decreased insoluble sugars and carbohydrates in ‘Superior' seedless grape leaves. Applying Brs at concentrations of 0, 1, 2, and 3 mg/l twice during the berry development stages (pea and veraison) enhanced the plants’ ability to withstand PC-induced stress. The concentration of 3 mg/l Brs elevated some metabolic activities, including insoluble sugar, total carbohydrates, proline, and total phenol. Additionally, it increased the antioxidant enzyme activity. Meanwhile, 2 mg/l appeared to be the most effective concentration in achieving the highest cluster and berry weight, enhanced total soluble solids (TSS) and firmness, and reduced weight loss over shelf life. In conclusion, applying Brs could be a promising strategy to alleviate the adverse effect of abiotic stress on table grapes.