Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 2005
Publication Date: June 1, 2006
Citation: Ehlenfeldt, M.K., Ogden, E.L., Rowland, L.J., Vinyard, B.T. 2006. Evaluaton of mid-winter cold hardiness among 25 rabbiteye blueberry (vaccinium ashei reade) cultivars. HortScience. 41:579-581. Interpretive Summary: Rabbiteye blueberries are a type of cultivated blueberry adapted to the southern U.S. When breeding cultivars for adaptation to the broadest possible range of environmental conditions it is useful to know the cold hardiness of the parental materials. For this study, the mid-winter cold hardiness of 25 rabbiteye blueberry cultivars was evaluated across two years by freezing shoots at various temperatures and determining the temperature that destroys 50% of the flower buds. Cold hardiness values were found to range from -24.9C for ‘Pearl River’ (a 50% rabbiteye type) to -13.7C for ‘Chaucer’ (100% rabbiteye). Under New Jersey conditions, many rabbiteye cultivars were observed to exhibit differing flower bud sizes. Variable flower bud size was found to be more common in less hardy cultivars. This information will be of use to scientists breeding for hardier rabbiteye cultivars and for extension workers who advise farmers on variety selection.
Technical Abstract: The mid-winter cold hardiness of 25 rabbiteye (V. ashei) blueberry cultivars was assayed across two years using a shoot freezing assay. LT50 values (i.e. temperature at which 50% of buds are damaged) for the cultivars ranged from -24.9 ºC for ‘Pearl River’ (a 50% V. ashei derivative) to -13.7 ºC for ‘Chaucer’. Under New Jersey conditions, numerous cultivars were observed to exhibit dimorphism for dormant floral bud size. Comparisons of bud dimorphism with LT50 values, found dimorphism more common in cultivars with lower floral bud hardiness. LT50 values generally supported empirical observations of winter hardiness, but exceptions suggest that additional factors contribute to “observed winter hardiness” under field conditions.