Proposal of double-cropping system for 'BRS Isis' seedless grape grown in subtropical area

Abstract

‘BRS Isis’ is a new colored seedless table grape tolerant to downy mildew, the main vine disease in subtropical humid areas. This new seedless cultivar is an interspecific hybrid from the crossing of CNPUV 681-29 [Arkansas 1976 × CNPUV 147-3 (‘White Niagara’ × ‘Venus’)] × ‘BRS Linda’. However, its performance under subtropical conditions hasn´t been assessed yet, especially under double annual cropping system. For this purpose, a research was designed with the objective to characterize the phenology and the main physicochemical properties of this new cultivar. The trial was carried out in a commercial vineyard of ‘BRS Isis’ seedless grape from 2-year-old vines grafted on ‘IAC 766 Campinas’ rootstock, located in Marialva, state of Paraná (PR), Brazil, in two consecutive crops, summer season 2016 and off-season 2017. The vines were trained on overhead trellises and spaced 2.0 × 5.0 m apart. The duration of the main phenological stages of ‘BRS Isis’ were evaluated from pruning until harvest, as well its thermal demand and main physicochemical characteristics. The summer and off-season crop cycles of ‘BRS Isis’ seedless grape grown under subtropical conditions last 144 and 125 days, with thermal demands of 1,931 and 1,815 degree days, respectively. This new seedless grape cultivar can be successfully grown under a double annual cropping system in subtropical conditions, however, as it is a very fruitful cultivar, it is necessary to perform a load crop adjustment after fruit set, equivalent to a density of 5 bunches.m−2, to obtain a sustainable yield in each season. Under this growing system, the berries present in both seasons, appropriate physicochemical characteristics for table grape market, but with darker skin color in off-season. Based on these results, a detailed double annual cropping system, with some specific cultural practices, is proposed for this new hybrid seedless cultivar.