Pollen Fertility of Hybrids Between Rabbiteye Blueberry and Vaccinium Constablaei

Abstract

Vaccinium asheiReade, the cultivated rabbiteye blueberry of the southeastern United States, was hybridized with V. constablaeiA. Gray, a lower-growing, highly rhizomatous blueberry native on the high mountain balds of western North Carolina and eastern Tennessee. Both species are hexaploid. The F ₁hybrids appeared to be fully male fertile based on copious pollen shed and on the high percentage of the pollen that could be stained with acetocarmine dye. Twelve F ₁plants representing three crosses averaged 97% pollen staining, compared to 96% for V. asheiand 95% for V. constablaei. Crosses of tetraploid southern highbush selections (largely V. corymbosumL.) with V. constablaeiproduced F ₁hybrids that shed little pollen and averaged only 48% pollen staining. The low pollen fertility was probably due to differences in chromosome numbers between the parental species. Unreduced gametes were detected in V. constablaeiand were probably involved in the evolution of V. constablaeifrom diploid and tetraploid species. Vaccinium constablaeihas several desirable traits needed in rabbiteye blueberry cultivars, including short stature, low bloom-to-ripe heat unit requirement, small seeds, and inconspicuous sclereids. Because the interspecific hybrids are highly fertile, it is likely that hexaploid blueberry cultivars of the future will increasingly contain a mixture of genes from the two species.