Development of 'Itália Melhorada' grapes on different rootstocks and under the semiarid conditions of the Rio Grande do Norte State, Brazil

Our study was carried out in the region of Mossoro city, state of Rio Grande do Norte (Brazil), in February 2013. This experiment aimed to describe the phenology, estimate biometeorological indexes, and perform a chemical characterization of 'Italia Melhorada' grapes (Vitis vinifera L) grafted on three different rootstocks (cultivars: IAC 313, IAC572, and IAC766), during two production cycles and under semiarid conditions. The first cycle lasted 115 days, with a pruning performed on 04/19/2013; yet the second lasted 111 days, with a pruning on 09/25/2013. In the first cycle, the thermal sum required was 1258.27 DD (degree days), while in the second, it was 1290.50 DD. The Heliothermic Geslin Index (HGI) observed in the first cycle was 352.84 and, in the second, it was 371.17. The rootstocks had no influence on the evaluated factors (phenology, TTA, TSS, and STT/ TTA) in either of the two cycles, therefore, all the tested rootstocks can be used indistinctly, but still, the analysis revealed differences from one cycle to another in terms of TSS and TSS / TTA of berries.