Comparison of methods for estimation of chilling and heat requirements of nectarine and peach genotypes for flowering

Chilling and heat requirements for breaking dormancy and flowering were studied in 63 nectarine and 118 peach genotypes (Prunus persica (L.) Batsch) for seven years. We compared two methods for estimation of requirements and four models for calculation of chill accumulation: Chilling Hours (CH), Chilling Units (CU), Positive Chilling Units (PCU) and Dynamic, while heat accumulations were estimated in growing degree hours (GDH). Additionally, correlations between chilling requirements, heat requirements and flowering date were established. Our results suggest that the Luedeling model is better than the Alonso model to estimate chilling and heat requirements in our field conditions. Moreover, it is recommendable to calculate the chill accumulation in accordance with the Chilling Hours or Positive Utah models. Additionally, since chilling requirements were positively correlated with flowering dates, they seem to be important to regulate blooming in nectarine and peach genotypes. (C) 2014 Elsevier B.V. All rights reserved.