Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 12, 2010
Publication Date: February 1, 2011
Citation: Okie, W.R., Blackburn, B. 2011. Increasing chilling reduces heat requirement for floral budbreak in peach. HortScience. 46:245-252. Interpretive Summary: Successful peach production requires selection of varietes that bloom at the appropriate time for a particular area. Time of bloom depends on the genetically determined chilling requirement of the variety, as well as the patterns of cold and warm temperatures through the winter. This research shows that higher amounts of winter chilling allow the tree to bloom with lesser amounts of warm temperatures, at least up to a certain point. Early in the process, extra chill greatly reduces heat required. Later, the exchange is about one to one. After this point, additional chilling delays bloom. In moderate climates and relatively low-chill years, bloom will be extended. In high chill areas and years, bloom will occur more rapidly and the time from start to finish will be less.
Technical Abstract: Response to chilling temperatures is a critical factor in the suitability of peach [Prunus persica (L.) Batsch] cultivars to moderate climates such as in the southeastern United States. Time of bloom depends on the innate chilling requirement of the cultivar as well as the timing and quantity of cold and warm temperatures experienced by the buds. Most current chilling models have considered dormancy break a sequential process: after appropriate chilling is received, a fixed amount of heat will produce bloom. This research shows that as chilling exposure increases, the time and heat required for floral budbreak decreases in an exponential relationship. In high-chill years and locales, the two-part model is adequate. In lower-chill situations, the curvilinear relationship, in conjunction with the range of chill requirement found among the buds on a single twig, affects the pattern of bloom. Budbreak requires more heat and is more extended.