Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2007
Publication Date: July 1, 2007
Citation: Ehlenfeldt, M.K., Rowland, L.J., Ogden, E.L., Vinyard, B.T. 2007. Cold Hardiness of Vaccinium ashei, V. constablaei and Hybrid Flower Buds and the Potential for Producing Northern-Adapted Rabbiteye Cultivars. HortScience. 42:1131-1134.
Interpretive Summary: Vaccinium ashei is a vigorous, but late-ripening type of blueberry grown commercially in the southern U.S. Although this species of blueberry has some desireable characteristics, it can not be grown in the northern U.S. because its flower buds are easily destroyed by freezing temperatures. However, the wild blueberry species V. constablaei is exceptionally cold hardy, and when it is crossed to V. ashei, the hybrids flower later but ripen earlier, and are considerably more winter hardy than V. ashei. These hybrids have the potential to be grown in more northern climates. In this study we determined the temperature at which flower buds were killed by freezing in a series of hybrids composed of varying percentages of these two species. A combination of 25% V. constablaei and 75% V. ashei appears suitable to develop northern-adapted V. ashei types. This information will guide blueberry breeding programs interested in developing northern adapted blueberry varieties. In order to increase the range of blueberry varieties available for production in northern regions and increase the supply of fruit to the consumer.
In 2004 to 2006, cold hardiness assays were performed to evaluate the relative winter hardiness in V. ashei Reade and V. constablaei Gray, as well as in selections/families composed of various combinations of V. ashei and V. constablaei germplasm. Significant differences were observed among entries, with LT50 values ranging from -17.2° C to -28.4° C. An analysis of LT50 vs. % V. constablaei yielded a regression of LT50(°C) = (-0.083 x V. constablaei percentage) – 21.574. Families or selections with 50% (or greater) V. constablaei, and some with 25% V. constablaei had LT50 values equivalent to, or better than ‘Bluecrop’. Based upon this information, a 25% V. constablaei constitution appears suitable to develop northern-adapted rabbiteye types, if proper parents are selected and if sufficient selection pressure/evaluation for winter hardiness is exercised.