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BACKGROUND Obtaining two or more successive annual vintages from the same vineyard is characteristic of regions with a tropical climate, such as the Submedio of the Sao Francisco Valley, Brazil. The present study aimed to characterize the chemical composition of grapes in four production cycles (i.e. two calendar years) when considering the interaction between cv. Syrah and two rootstocks. For a broad characterization, two methodologies for the extraction of phenolic compounds were used, as well as different methods of analysis. RESULTS The results obtained showed that there was an influence of rootstock and harvest season. Grapes from vines grafted onto IAC 313 contained higher concentrations of total condensed tannins (skins) and flavanols than grapes from vines grafted onto 1103P. However, the grape samples from the vines grafted onto 1103P contained higher levels of monomeric anthocyanins than the grape samples from the vines grafted onto IAC 313. The first harvest season was characterized by higher concentrations of most phenolic compounds than the second harvest season. CONCLUSION In the present study, it was possible to confirm that, in the semiarid region of Brazil, the interaction between the cultivar Syrah and the different rootstocks, as well as the climatic conditions in each harvest season, influenced the composition of the grapes, mainly in relation to phenolic compounds. (c) 2019 Society of Chemical Industry