Cold hardiness of southern-adapted blueberry genotypes and the potential for their use in northern adapted blueberry breeding

Authors: Ehlenfeldt, Mark; Rowland, Lisa; Ogden, Elizabeth; Vinyard, Bryan

Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2008
Publication Date: 6/1/2009
Citation: Ehlenfeldt, M.K., Rowland, L.J., Ogden, E.L., Vinyard, B.T. 2009. Cold hardiness of southern-adapted blueberry genotypes and the potential for their use in northern adapted blueberry breeding. Plant Breeding. 128:393-396.

Interpretive Summary: As cultivated blueberry germplasm becomes more diverse, there is increased concern whether varieties are sufficiently cold hardy for certain regions of the country, especially if southern-adapted germplasm comprises a significant part of the ancestry, as it does for some newer types. To answer this, twelve southern-adapted blueberry genotypes were evaluated for mid-winter cold hardiness using a shoot freezing assay. Significant differences were seen among the varieties tested, but observations suggested that varieties selected in North Carolina might typically have enough cold hardiness to be used without concern in developing northern varieties. Other more southern-adapted varieties were generally less hardy and would need to be used with greater care and have stricter evaluation for cold hardiness in offspring if they were used as parents. This information will be of use to those developing new varieties who wish to use southern-adapted parents, and for those who might consider growing the tested varieties in marginal areas.

Technical Abstract: Twelve southern-adapted blueberry genotypes, both southern highbush and rabbiteye, were evaluated for mid-winter cold hardiness using a shoot freezing assay. Significant differences in LT50 values were observed among the genotypes, ranging from -11.9 °C for ‘Millennia’, a southern highbush cultivar, to -25.5 °C for ‘Reveille’, another southern highbush variety. Differences between years appeared to be related to differences in weather conditions that also led to differences in bud development. December and the first half of January, winter of 2006-2007, was particularly warm leading to higher bud development scores for several of the genotypes and apparently loss of freezing tolerance. Observations suggested that germplasm selected in North Carolina might typically have enough cold hardiness to be used without concern in northern breeding. Other more southern germplasm was generally less hardy and would need to be used with greater care and have stricter evaluation of cold hardiness in offspring.