Study on the regulation of anthocyanin biosynthesis by exogenous abscisic acid in grapevine

Anthocyanins are important components not only for the red wine and table grapes, but also for the antioxidant capacity and disease prevention. The aim of this work was the investigation of the regulation mechanism of exogenous hormones on anthocyanins. The experiment took place in 2016, in a vineyard located in Ningxia (China). Chemical analysis, high-performance liquid chromatography (HPLC) and transcriptional studies were carried out to clarify the anthocyanin biosynthesis regulation. Vitis vinfera L.cv. 'merlot' in four treatments: 300, 600 and 900 mg L-1 exogenous abscisic acid (ABA) were sprayed to clusters respectively on 50 days after full bloom, equal volume of distilled water were sprayed as control group. Grape samples were collected at five berry development stages from veraison to harvest. Anthocyanin quantification and characterization were detected by spectroscopy and HPLC. Quantitative real-time (qRT-PCR) was carried out to clarify the expression levels of structural and regulatory genes. Compared with the control group, 600 mg L-1 ABA significantly increased the content of Malvidin-3-O-glucoside after veraison. The content was 6.02 mg g(-1) at fruit maturity, which was 1.45 times of the control. During ripening, the methoxylated pigments was enhanced by 300 and 600 mg L-1 ABA treatments. The expression of PAL, F3'H, F3'5'H, UFGT and MybAl genes were positively induced by 600 mg L-1 ABA. The ratio changes between Delphinidin-3-acelylglucoside and Cyanidin-3-acelylglucoside were associated with the proportion of F3'5'H/F3'H gene expression. A positive correlation among anthocyanin contents and different sugars has been identified as well. Thus, ABA, sugars and relevant genes play the important roles on grape coloring and 600 mg L-1 ABA treatment was optimal for accumulating anthocyanins in 'merlot' grape.