Differential thermal analysis sheds light on the effect of environment and cultivar in peach floral bud cold hardiness

Reduction of fruit production due to cold damage in floral tissues is the greatest threat to profitability of tree fruit industries in Colorado, and across much of the US. This study identified the critical temperatures of peach buds during the different phases of dormancy. Cold hardiness, expressed as lethal temperature for 10% (LT₁₀), 50% (LT₅₀), or 90% (LT₉₀) loss of peach buds was quantified with differential thermal analysis (DTA). Two peach cultivars including ‘Sierra Rich’ and ‘Cresthaven’ were tested during late fall to early spring. Cold hardiness followed a predictable seasonal pattern in both cultivars tested: an acclimation phase in late fall, a period of maximum hardiness in winter (mid-December to late January), and de-acclimation going into spring. Temperature fluctuations led to considerable ‘noise’ in this general trend. Sudden freezing events induced hardiness and unseasonal warm temperatures induced temporal deacclimation. ‘Sierra Rich’ was the least hardy and showed minimum response to freezing events and deacclimated faster as a response to unseasonal warm temperatures, compared to ‘Cresthaven’. DTA analysis successfully predicted field bud damage on ‘Sierra Rich’ during the winter and spring of 2016-17. During bud swell, DTA was not an effective method for detecting low-temperature exotherms in peach buds. The information that was generated in this study will provide a better understanding of peach cold hardiness and will support growers in decision-making for frost control practices and estimate potential losses.