Chilling Requirement of Ten Peach Cultivars Estimated by Different Models

The adaptation of a temperate climate fruit cultivar to a certain area depends mainly on its chilling requirement and the chilling accumulation in such places. Several attempts have been made to estimate these two conditions, using different models. The great variation among the models to calculate chilling requirement makes it necessary to determine their efficiency in a given location. Aiming to estimate the chilling requirement of ten peach cultivars, including Bonão, Pepita, Maravilha, Precocinho, Turmalina, Diamante, BR-3, Marfim, Coral, and Cambará do Sul, seven models were tested: Utah, Positive Utah, Low Chill, Taiwan, Chilling Hours (≤7.2°C), Chilling Hours (≤11°C), and Dynamic. The results showed that the estimation of chilling accumulation for all the studied cultivars in all the tested models showed a large variability. None of the tested models was perfect for estimating the chilling requirement, especially considering the variable climatic conditions of southern Brazil. Except for the Utah model, any of the others can be used to provide a rough estimate of the chilling requirement of the cultivars; however, the Taiwan and Low Chill models seem to be more suitable. The chilling requirement, which was estimated based on the average over the 11 years of the study, overestimated the real need, when compared to the yields over those years. There are differences among the studied cultivars; however, with the exception of Cambará do Sul, all the others can yield good crops and show good adaptation to the climatic conditions of the southern Rio Grande do Sul.