Dormancy is an important strategy in perennial plants such as the tree fruit peach (Prunus persica), to protect them from damage during harsh environmental conditions such as winter weather. As day length and temperature decrease in the fall, floral and vegetative buds enter a state of endodormancy where they remain unresponsive to growth promoting environmental signals (Nilsson, 2022). Exposure to cold temperatures (typically ≤ 7° C) during the winter allows for chill accumulation and upon sufficient such chill accumulation, release from endodormancy occurs. This is followed by exposure to warmer temperatures in the spring leading to the end of eco- dormancy and bud break. In the field, low winter temperatures are often interspersed with periods of substantially warm weather thereby interrupting or negating the progression of chill accumulation and affecting bud break in the spring. Understanding responses of peach buds to intermittent warm temperature exposure is needed to mitigate crop loss due to temperature fluctuations. Experiments were conducted to determine the effects of such intermittent warm temperature exposure on chill accumulation in ‘Contender’ peach. Potted trees were maintained at ambient conditions in the field until around 50% of chill requirements (100 % = 1050 chill hours) were met. Following this, trees were subjected to one of three treatments: Control, Chill break I, and Chill break II, with 4 replicates per treatment. The Control group of peach trees were maintained under ambient conditions to reach their chill requirement. Chill break I and Chill break II were exposed to intermittent warm temperatures of continuous 14 °C in a growth chamber for 7 and 14 days, respectively. Following the treatment, trees were returned to ambient conditions. Peach buds were collected from each treatment at three stages and remaining buds were monitored to track floral bud break progression. Additionally, we determined the metabolite and phytohormone concentrations in ‘Contender’ peach buds that naturally accumulated their chilling requirements. Results indicate that as chilling progression increases, starch concentration increases. Concentration of the phytohormone ABA (abscisic) acid appeared to decrease upon completion of endodormancy. Together, these analyses are expected to help us gain a better understanding of dormancy progression in peach.
