Using brassinolide and girdling combined application as an alternative to ethephon for improving color and quality of 'Crimson Seedless' grapevines

Abstract

AbstractThe color of 'Crimson Seedless' berries is a major constraint in expanding marketing and export potential. The target of this investigation is to enhance the color and quality of 'Crimson Seedless' by using brassinolide (BL) and girdling treatments, individually and in combination, as an alternative to ethephon over two consecutive seasons. The obtained results revealed that the combined treatment BL at 2.0 mg/L and girdling recorded the highest significant yield values (17.78 ± 0.29 and 18.26 ± 0.23 kg/vine) in both seasons, respectively, in contrast to ethephon and girdling treatments which had no significant influence. Besides, BL 2.0 mg/L + girdling presented high levels of physicochemical characteristics of clusters and berries compared to the control. Concerning berry color assessment, ethepon followed by BL at 2.0 mg/L + girdling recorded the highest significant improvement in the red color, as indicated by Color Index of Red Grapes and visual assessment, and had similar and elevated levels of anthocyanin content. On the other hand, flavonoids (3.46 ± 0.03 and 3.66 ± 0.02 mg/100 g FW), and antioxidant capacity (2.37 ± 0.02 and 2.43 ± 0.06 IC50) were obviously increased with BL 2.0 mg/L + girdling, with a slight decrease than ethephon application. As for phenylalanine ammonia-lyase activity, the data show that it increased by ethephon (7.91 ± 0.02 and 8.01 ± 0.02 U mg−1protein) and BL 2.0 mg/L + girdling (7.77 ± 0.04 and 7.79 ± 0.07 U mg−1protein), compared to the control (3.69 ± 0.02 and 3.80 ± 0.01 U mg−1protein) in both seasons, respectively. In terms of polyphenol oxidase activity, the increase in PPO was closely associated with PAL. Moreover, BL 2.0 mg/L + girdling was the most effective treatment for increasing dormant season parameters in both seasons, while ethephon spraying had no influence. All these confirmed that the combined treatment BL 2.0 mg/L + girdling exhibited a synergistic effect in improving the color and quality of 'Crimson Seedless'.