Highbush blueberry (Vaccinium corymbosum L.) cultivars are considered, in general, to be adequately self-fertile/self-fruitful (Merrill, 1936); however, numerous studies have demonstrated the value of cross-pollination to fruit set, fruit size, development time, etc. (Coville, 1921; Ehlenfeldt, 2001; Meader and Darrow, 1947). In contrast, rabbiteye blueberry (V. ashei Reade) cultivars are considered overwhelmingly self-incompatible (Brightwell et al., 1955; El-Agamy et al., 1981) and critically dependent on cross-pollination (Meader and Darrow, 1944), although some indications of self-fertility in rabbiteye have been noted (Krewer and NeSmith, 2006).
In breeding for improved cold-hardiness in rabbiteye blueberry types, we have selected clones that we have termed NRE (Ehlenfeldt et al., 2007, 2012). These selections are a composite of several species: 6x V. ashei (rabbiteye), a vigorous hexaploid species native to the southeastern United States as well as Texas; 6x V. constablaei, a self-fertile, highbush-like, high-altitude species found in northern Georgia, western North Carolina, and eastern Tennessee; 2x V. darrowii, a low-chill species native to Florida and adjacent states that has been used in the development of southern highbush; and 4x V. corymbosum, the northern-adapted species considered to be typical highbush blueberry, native to a wide range of temperate areas in the eastern third of North America. Considerable vigor is imparted to NRE selections by the V. ashei component, and these selections are envisioned as possible late-season alternatives to highbush cultivars. Rabbiteye blueberry acreage has remained relatively stagnant in acreage in the southern United States, whereas the acreage of earlier ripening southern highbush cultivars has increased (Strik and Yarborough, 2005). At the same time, growers in some more northern areas such as New Jersey and Oregon are experimenting with some of the more robust traditional rabbiteye cultivars (i.e., not northern-adapted) as a way to extend the fruiting season (Ehlenfeldt, personal observation). One critical piece of information to know about NRE selections is how they compare with highbush and rabbiteye with respect to self-fertility and their relative need for cross-pollination.
Twelve selections of varied composition were chosen for this study: four NRE selections, four rabbiteye (RE) cultivar standards, two rabbiteye × V. constablaei (RE-CON) hybrids, and two highbush standards (HB). These selections were compared, when either self- or cross-pollinated, for fruit set, berry weight, and seed development.
Bates, D., Maechler, M. & Bolker, B. 2011 lme4: Linear mixed-effects models using S4 classes. R package version 0.999375-42. <http://CRAN.R-project.org/package=lme4>
Brightwell, W.T., Woodard, O.J., Darrow, G.M. & Scott, D.H. 1955 Observations on breeding blueberries for the Southeast Proc. Amer. Soc. Hort. Sci. 65 274 278
Coville, F.V. 1921 Directions for blueberry culture. U.S. Dept. of Agr. Bul. 974
Ehlenfeldt, M.K., Rowland, L.J., Ogden, E.L. & Vinyard, B. 2012 Cold-hardiness, acclimation, and deacclimation among diverse blueberry genotypes J. Amer. Soc. Hort. Sci. 137 31 37
Ehlenfeldt, M.K., Rowland, L.J., Ogden, E.L. & Vinyard, B.T. 2007 Floral bud cold hardiness of Vaccinium ashei, V. constablaei, and hybrid derivatives and their potential for producing northern-adapted rabbiteye cultivars HortScience 42 1131 1134
El-Agamy, S.Z.A., Sherman, W.B. & Lyrene, P.M. 1981 Fruit set and seed number from self- and cross-pollinated highbush (4x) and rabbiteye (6x) blueberries J. Amer. Soc. Hort. Sci. 106 443 445
Krewer, G. & NeSmith, D.S. 2006 Blueberry cultivars for Georgia. Oct. 2006, <http://www.smallfruits.org/Blueberries/production/06bbcvproc_Nov0206.pdf>
Lyrene, P.M. 1993 Rabbiteye blueberry cultivar ‘Snowflake’. U.S. Plant Patent 8,082, filed 10 Jan. 1991 and issued 5 Jan. 1993
Merrill, T.A. 1936 Pollination of the highbush blueberry. Mich. Agr. Expt. Sta. Tech. Bul. 181
R Development Core Team 2011 R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. <http://www.R-project.org/>
Strik, B.C. & Yarborough, D. 2005 Blueberry production trends in North America, 1992 to 2003, and predictions for growth HortTechnology 15 391 398
U.S. Dept. of Agriculture 1996 Notice of release of ‘Little Giant’ hybrid blueberry. USDA, Beltsville, MD