Chilling and heat requirement of peach cultivars and changes in chilling accumulation spectrums based on 100-year records in Republic of Korea

Abstract

Chilling and heat requirements of peach cultivars and spectrums of chilling accumulation over the last 100 years (1919–2018) were evaluated to determine phenological characteristics for dormancy break in Republic of Korea. Chilling requirement was calculated by using Chill Hours, Utah, Dynamic, North Carolina, and Low Chilling models and heat requirement was estimated in growing degree hours (GDH). Chilling requirement of 15 cultivars ranged between 263 and 2123 chill hour (CH), 377 and 1134 chill unit (CU), and 21.3 and 74.8 chilling portion (CP). The Dynamic model showed the highest precision with the smallest variation among years, followed by the Utah model. Heat requirement ranged from 4824 to 5506 GDH and was positively correlated with flowering date. During last 100 years, the initiation date of chilling accumulation had been delayed for 10–12 days in Chill Hours and Utah models. In contrast, the Dynamic model showed no significant changes in chilling accumulation spectrum. Although the chill accumulation was enough to fulfill the chilling requirement so far in Republic of Korea, reduced chills were monitored from 100-year data. Therefore, continuous monitoring or estimation of chilling accumulation in the future is needed.