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 and118 peach genotypes (Prunus persica (L.) Batsch) for seven years. We compared two methods for estima-tion of requirements and four models for calculation of chill accumulation: Chilling Hours (CH), ChillingUnits (CU), Positive Chilling Units (PCU) and Dynamic, while heat accumulations were estimated in grow-ing degree hours (GDH). Additionally, correlations between chilling requirements, heat requirements andflowering date were established. Our results suggest that the Luedeling model is better than the Alonsomodel to estimate chilling and heat requirements in our field conditions. Moreover, it is recommend-able 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 tobe important to regulate blooming in nectarine and peach genotypes. Fil: Maulión, Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Centro de Estudios Fotosintéticos y Bioquímicos (i); Argentina Fil: Valentini, Gabriel Hugo. Instituto Nacional de Tecnologia Agropecuaria. Centro Reg.buenos Aires Norte. Estacion Exptal.agrop.san Pedro; Argentina Fil: Kovalevski, Leandro. Universidad Nacional de Rosario. Facultad de Cs.economicas y Estadistica. Escuela de Estadistica; Argentina Fil: Prunello, Marcos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina Fil: Monti, Laura Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Centro de Estudios Fotosintéticos y Bioquímicos (i); Argentina Fil: Daorden, María Elena. Instituto Nacional de Tecnologia Agropecuaria. Centro Reg.buenos Aires Norte. Estacion Exptal.agrop.san Pedro; Argentina Fil: Quaglino, Marta. Universidad Nacional de Rosario. Facultad de Cs.economicas y Estadistica. Escuela de Estadistica; Argentina Fil: Cervigni, Gerardo Domingo Lucio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Centro de Estudios Fotosintéticos y Bioquímicos (i); Argentina