Maturation and quality of BRS Magna grapes influenced by rootstocks in rainy season.

Seasonal variations and production factors can influence the quality of grapes. Considering the Sub-middle region of the São Francisco Valley, Brazil, differentiated by production in rainy and warmer periods of the year, the climatic conditions in each season affect the duration of the phenological phases and quality of the grapes. The objective of this study was to characterize the changes in the quality components during maturation of BRS Magna grapes on different rootstocks, in rainy seasons under tropical conditions, as a support to define the harvest time. The experiment was conducted in Petrolina, Pernambuco, Brazil, from Jan to Apr 2017 (cycle 1) and Dec 2017 to Apr 2018 (cycle 2) evaluating rootstocks and age of the fruits. Bunches were picked from the start of maturation to the harvest: 49, 56, 61, 64 and 68 days after fruit set (DAF) for cycle 1, and 35, 41, 48, 55, 61, and 66 DAF for cycle 2. In cycle 1 IAC 572? and ?Paulsen 1103? rootstocks provided higher sugar contents in grapes, which was only repeated in cycle 2 for Paulsen 1103. The accumulation of anthocyanins and yellow flavonoids was favored by ?IAC 313? and IAC 572 rootstocks in cycle 1, and by ?IAC 313? and ?IAC 766? in cycle 2. A higher content of polyphenols was conferred on IAC 572 in cycle 1 and on IAC 766 in cycle 2, which also had a greater antioxidant capacity. Although there were differences between rootstocks, harvesting at approximately 64 DAF maximized grape quality for all treatments