Submitted to: New Jersey Annual Vegetable Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 27, 2004
Publication Date: January 17, 2005
Citation: Ehlenfeldt, M.K. 2005. Winter-hardiness and deacclimation behavior of diverse blueberry (vaccinium spp.) genotyped under field conditions. New Jersey Annual Vegetable Meeting Proceedings. Interpretive Summary: Late-winter bud-hardiness is important to the success of blueberry varieties because late-winter thaws followed by hard freezes can cause severy injury to flower buds. A study was undertaken to investigate bud-cold-hardiness under field conditions for 12 diverse commercial blueberry varieties and a cold-adapted species. There were clear differences in cold-hardiness among varieties. The results suggest that several southern cultivars may be suitable to grow under more northern conditions. Additionally, the cold-adapted species may be useful in breeding for improved cold-hardiness and greater spring-frost tolerance. These results will be of use to northern growers wishing to experiment with growing southern varieties, and to researchers working to develop more cold-hardy blueberry varieties.
Technical Abstract: Deacclimation response is an important part of adaptative success in blueberries because late-winter thaws followed by hard freezes can cause severe injury to flower buds. A study was undertaken to investigate cold-hardiness and deacclimation behavior under field conditions for 12 diverse blueberry genotypes including 'Weymouth', 'Duke', 'Bluecrop', 'Legacy', 'Ozarkblue', 'Northcountry', 'Northsky', 'Little Giant', 'Magnolia', 'Pearl River', 'Tifblue', and a population of V. constablaei. These selections have different germplasm compositions and different expected mid-winter bud-hardiness levels. Bud cold-hardiness versus weeks of deacclimation was examined over a seven-week period in two consecutive years (2002 - 2003). There were clear genotypic differences in cold-hardiness and timing of deacclimation. Among the highlights: 1)'Legacy' was the least cold-hardy at initial evaluation, less so even than 'Tifblue', 2) 'Duke' was an 'early deacclimator'; however, it started at such a low initial level that this early deacclimation did not represent a significant detriment, 3) 'Ozarkblue' (southern highbush) was not significantly different from cultivars like 'Bluecrop' and 'Weymouth' in its deacclimation behavior, 4) 'Magnolia' (southern highbush) also appeared to have cold-hardiness and deacclimation behavior comparable to northern highbush cultivars, 5)V. constablaei was particularly cold-hardy and late to deacclimate. 'Little Giant', a 50:50 hybrid of V. constablaei and V. ashei, was also extremely cold-hardy, and second only to the 100% V. constablaei selections in its lateness of deacclimation, and 6) a strong positive correlation was found between bud cold-hardiness and stage of bud opening (r = 0.84). These results suggest that several southern cultivars may be suitable to grow under more northern conditions. Additionally, V. constablaei may be useful in breeding for cold-hardiness, late-deacclimation, and greater spring-frost tolerance.