Unraveling the pathways influencing the berry color and firmness of grapevine cv. Flame Seedless treated with bioregulators using biochemical and RNA-Seq analysis under semi-arid subtropics

Plant bioregulators (PBRs) regulate developmental and physiological processes in plants. In this study, biochemical and transcriptomic analyses were conducted to evaluate the influence of PBRs [abscisic acid (ABA), benzothiadiazole (BTH), ethephon, and prohexadione-calcium (Pro-Ca)] on the grapevine cv. Flame Seedless under semi-arid subtropics. This study aims to see the effect of exogenous application of PBRs on overall berry quality, including uniformity of berry color. Uniform colored berries, the maximum total soluble solids (TSS) and total antioxidant activity (TAoA), and the highest total phenolics (TPC) and flavonoids (TFC) contents were obtained with the treatments, namely, 400 mg L^-1 ethephon and 400 mg L^-1 ABA. Further, RNA-Seq analysis has also identified some key DEGs like UFGT (VIT_16s0039g02230), GST (VIT_04s0079g00690), and chalcone synthase (CHS) (VIT_05s0136g00260) which were part of the anthocyanin biosynthesis pathway controlling grape berries color. Thus, ethephon (400 mg L^-1) and ABA (400 mg L^-1) were found promising for attaining greater uniformity in berry color development because of increased total anthocyanins content. In addition, they were also found associated with enhanced TAoA, TPC, and TFC. Hence, ethephon and ABA can be recommended for improving the berry quality.