Variation among highbush blueberry cultivars for frost tolerance of open flowers

Authors: Rowland, Lisa; Ogden, Elizabeth; Takeda, Fumiomi; Glenn, David; Ehlenfeldt, Mark; Vinyard, Bryan

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2013
Publication Date: 6/15/2013
Publication URL: http://handle.nal.usda.gov/10113/58557
Citation: Rowland, L.J., Ogden, E.L., Takeda, F., Glenn, D.M., Ehlenfeldt, M.K., Vinyard, B.T. 2013. Variation among highbush blueberry cultivars for frost tolerance of open flowers. HortScience. 48(6):692-695.

Interpretive Summary: Like many fruit crops in the U.S., blueberry yields can be significantly reduced by frost damage to open flowers. These damaging frosts are expected to be on the rise as a result of higher than average winter temperatures in recent years. If temperatures warm prematurely in the winter, flower buds can begin opening, leaving sensitive flowers vulnerable to late winter or early spring frosts. In this study, the frost tolerance of open flowers of five highbush varieties, ‘Bluecrop’, ‘Elliott’, ‘Hannah’s Choice’, ‘Murphy’, and ‘Weymouth’, was determined using two different methods, one utilizing whole plants placed in frost chambers and the other utilizing cut shoots placed in a freezing bath. Results indicated there were small, but significant, differences in frost tolerance of open flowers. Overall, ‘Bluecrop’ was the most sensitive to freezing while ‘Hannah’s Choice’ and ‘Murphy’ were the most freezing tolerant. Both methods gave similar results. In conclusion, differences in frost tolerance of open flowers were found that will be of value to breeders for developing new varieties that are more tolerant to late winter/early spring frosts.

Technical Abstract: Injury of open flowers often occurs in fruit crops by late winter or early spring frosts and can result in significant reduction in yield. In this study, freezing tolerance of open flowers of five highbush blueberry cultivars, ‘Bluecrop’, ‘Elliott’, ‘Hannah’s Choice’, ‘Murphy’, and ‘Weymouth’, was determined using two freezing methods. Methods involved either placing whole plants in a radiation frost chamber or detached shoots in a glycol-freezing bath. In both methods, plants (or excised shoots) with opening flowers were exposed to temperatures ranging from -2 ºC to -10 ºC. After freeze treatments, several flower parts were evaluated for damage and the Lethal Temperature50 (LT50) determined. In order, from the most sensitive flower part to the least sensitive on average, were the corolla, filament, anther, style, external ovary, stigma, ovules, internal ovary, and placenta. A two-way ANOVA found no significant effect of the freezing method on the calculated freeze damage to most of the various flower parts. However, a significant genotype effect was found on freeze damage to the style, filament, anthers, and external ovary. Overall, ‘Bluecrop’ was the most sensitive to freezing while ‘Hannah’s Choice’ and ‘Murphy’ were the most freezing tolerant. In conclusion, genotypic variability in frost tolerance of open highbush blueberry flowers was detected which can be exploited in breeding for more frost tolerant varieties.