Modification of the source relationship and its influence on the primary and secondary metabolism in Tannat grapes

Abstract

In this study, the response of Tannat, an emblematic variety of the Uruguay, to the modification of the source relationship (S/S) was evaluated, through the leaf removal on fruit set and thinning of clusters at veraison, measuring the composition of the grape. The tests took place in a commercial vineyard (34º53’S, 56º19’W) and the results correspond to the years 2012 and 2013. Four treatments were defined: Control without intervention (T) Cluster thinning at veraison (R) and leaf removal on fruit set and cluster thinning at veraison (R+D). The experimental design consisted of complete random blocks, with 5 replicates and the experimental unit of 7 plants per treatment. Weekly sampling of 250 berries was carried out from veraison to harvest to determine: total soluble solids (TSS) and titratable acidity (AT), and at harvest the polyphenolic compounds. The concentration of SST was significantly higher in R and “R+D” for both years (p=0.0008 in 2012 and p=0.001 in 2013). The TA in 2012 did not show differences between treatments, and in 2013 R and “R+D” registered the lowest values (p≤0.001). For both years, potential and extractable anthocyanins (ApH1 and ApH3,2) were higher in “R+D”. The phenolic content presented differences in 2013, being higher in the “R+D” (p=0.003). The results indicate that the modification of the S/S balance increased the synthesis of primary and secondary compounds, when the two culture techniques were applied together.