Modeling the Budbreak in Peaches: A Basic Approach Using Chill and Heat Accumulation

Abstract

Phenological shifts in peaches have been observed over the last few years due to the fluctuation of the seasonal climate conditions experienced during dormancy, affecting orchard management practices and influencing production and harvest dates. This study aimed to model the vegetative and floral budbreak of selected peach cultivars. Three peach cultivars, including “Rubyprince”, “Harvester”, and “Red Globe”, were considered in this study based on the representation of the early, early-mid, and mid-seasons. The prediction of the budbreak in peaches was assessed using different models that integrate the combination of chill and heat requirements. Models used include the Weinberger model, the modified Weinberger model, Utah, the dynamic model, and the growing degree model. The accumulation of chill varies according to the season evaluated. A model that considers both chill and heat accumulation is presented for each cultivar. Budbreak as an indicator of dormancy completion was established for each cultivar. The outcome of this study is to determine the amount of chilling accumulation and thermal time required to mark the beginning of the budbreak in selected cultivars with a model that predicts the duration of the dormancy. These results are valuable information that can be used for crop management practices and support the mitigation of cold damage during this critical period of crop development.

Predicting Floral Bud Progression for Three Peach Cultivars

“…Thus, this study aims to predict the bud progression for three commercial peach cultivars using Growing Degree Days (GDD) from dormancy release (budbreak). The budbreak stage was previously calculated with the chilling and heat units needed to fulfil the requirements [21]. The peach floral bud progression is presented in detail and allows us to know that there is no synchronicity for the phenological stages because of the overlapping of several stages through time.…”

“…Ten-year-old peach trees of 'Rubyprince', 'Harvester', and 'Red Globe' cultivars were evaluated in this study. The cultivars were selected according to chilling hours (CH) requirements: 'Rubyprince', 850 CH; 'Red Globe', 850 CH; and 'Harvester', 750 CH [21].…”

“…According to progressive sampling collection (every week), buds accumulated different amounts of chilling hours from the field, simulating different winter scenarios in a previous study [21]. The budbreak stage was registered under laboratory conditions (2021-2022) and in growth chambers (2022-2023).…”

“…where TT is thermal time, accumulated from the first day (i) of the phenological stage occurrence until the day the next stage happens (n), and Tb represents the base temperature defined as the threshold at which the plant stops growing; in this case, 4.5 • C is widely referenced and used for peaches [21,[29][30][31]. GDD for the budbreak stage were calculated using a combination of the temperature from the field and controlled conditions due to the samples being collected gradually, using September 1 as a starting date.…”

“…Once the samples reached dormancy release during the first experiment [21], they remained in the laboratory under the same conditions. A database was created over time from daily observations to determine the time necessary to reach each subsequent phenological stage.…”