Estimation of Chilling Accumulation for Blackberry (Rubus sp.) Using Mathematical Models

As the climate change takes place, the cultivation of temperate climate crops in subtropical areas has become a challenge. The success of fruit crops, such as blackberry, in certain areas depends basically on its chilling requirement and the chilling accumulation in those areas. Usually the models used to predict those accumulations presents widely variable results being necessary to test the models in the location where the species is cultivated. The objective of this work was to estimate the chilling requirement for bud break of blackberry cultivars Caingangue, BRS Cainguá, Guarani, Tupy, BRS Xavante, BRS Xingu, Brazos, Cherokee and Choctaw, using the models of Utah, Positive Utah, Low Chill, Taiwan, Chilling Hours ≤7.2°C, Chilling Hours ≤11°C, and Dynamic and both temperature and phenological data from 2010 to 2019. The results showed a high variability in cold accumulation for all studied cultivars in all tested models. None of the models performed perfectly to estimate chilling requirement however, the Taiwan and the Utah Positive models can be used to provide a rough estimate of this requirement. On the other hand, Utah and Low Chill models are clearly not suitable for estimating blackberry chilling requirement. The estimated chilling requirement showed that all the studied cultivars are well adapted to the climatic conditions of the southern Rio Grande do Sul, which is emphasized by their good productivity in most of the years.