Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2011
Publication Date: 1/1/2012
Citation: Ehlenfeldt, M.K., Rowland, L.J., Ogden, E.L., Vinyard, B.T. 2012. Cold-hardiness, acclimation, and deacclimation among diverse blueberry (Vaccinium spp.) genotypes. HortScience. 137:31-37.
Interpretive Summary: Only limited evaluations have been done on the acquisition and loss of cold hardiness in blueberry, even though it is an important part of flower bud survival and fruiting success. In this study we have measured the timing and rate of cold hardiness development in fall and its loss in late winter-early spring in seven blueberry selections with varied ancestry. The primary differences observed among the seven selections were differences in hardiness levels, the date at which they were reached, and the date at which cold hardiness levels were no longer sustained and loss of cold hardiness occurred. Most northern types reached maximum cold hardiness in late December and maintained cold hardiness for numerous weeks thereafter. Most southern types reached maximum cold hardiness at the same date, but then began to lose cold hardiness despite the fact that daily mean temperatures were still decreasing. One hybrid that contained genes from northern and southern plant types maintained its cold hardiness similar to northern types, suggesting it is possible to develop southern types adapted to northern conditions. This information is useful to researchers trying to develop more cold hardy varieties, and to growers and researchers interested in understanding the areas of adaptation of currently available varieties.
Technical Abstract: Until recently, only limited evaluations have been done on the acclimation and deacclimation process in blueberry, even though it is an integral part of flower bud survival and, thus, reproductive success. In this study we have measured the timing and rate of acclimation and deacclimation in seven blueberry genotypes with different amounts of diverse species germplasm in their backgrounds. Primary differences observed among the seven genotypes were differences in maximum acclimation/hardiness levels and the date at which they were reached, and differences in the date at which maximum acclimation levels were no longer sustained and deacclimation commenced. ‘Bluecrop’, ‘Legacy’, ‘Tifblue’, and two rabbiteye-hybrid derivatives, US 1043 and US 1056, all reached maximum or near maximum cold acclimation by late December with LT50 temperatures in a range from -22 to -27 °C. ‘Northsky’ and ‘Little Giant’ both achieved cold acclimation of -28° C or below (the lowest value we could measure) by the end of November. After reaching their maximum acclimation in late December, ‘Legacy’, ‘Tifblue’, and US 1043 began a sustained and relatively linear deacclimation, whereas US 1056, ‘Bluecrop’, ‘Northsky’ and ‘Little Giant’ sustained their acclimation for longer intervals. ‘Bluecrop’ and US 1056 did not begin to deacclimate until early March, and ‘Little Giant’ and ‘Northsky’ had no LT50 values higher (warmer) than -25° C until late March. As concerns of climate change increase, knowledge of the ability of breeding germplasm to tolerate greater extremes and greater fluctuations will prove increasingly valuable.