24-Epibrassinolie Enhances the Effect of Calcium and Boron on Amelioration of Aril Browning Disorder in Pomegranate (Punica granatum cv. ‘Rabab’)

Abstract

Aril browning is a serious physiological disorder especially under environmental stress in pomegranate (Punica granatum cv. ‘Rabab’). Evidence shows that calcium (Ca), boron (B), and brassinosteroids (BRs) could improve cellular protection, stimulates anthocyanin biosynthesis, and reduce pulp browning. In this experiment, the simple and interactive effect of 24-epibrassinolide (EBR) on increasing the efficiency of Ca and B on improving the aril browning disorder in ‘Rabab’ pomegranate was investigated. A factorial experiment was conducted in a randomized complete block design with the exogenous foliar spray of EBR at two levels − 0 (Ctrl.), and − 0.4 mg L−1 and foliar nutrition contained − untreated (Ctrl.), − calcium chelate (2 g L−1), − boric acid (0.5 g L−1) and − calcium chelates (2 g L−1) + boric acid (0.5 g L−1). The foliar spray was applied a week before full bloom, 4 weeks after full bloom, and before the arils fully mature stage. The interactive effect of EBR1 + Ca + B had the highest influence on the reduction of the browning index (BI). This treatment significantly increases fruit total soluble solids (TSS), total anthocyanin, phenolic, and flavonoid content that had a negative correlation with the BI in cv. ‘Rabab’ pomegranate. Exogenous foliar spray of EBR significantly enhanced the effect of Ca and B on reducing the aril browning disorder, and this effect could be due to the improving the pollen function and fruit quality indices, which plays a very important role in controlling synthesis and preventing dissociation of anthocyanin.