As a first step in determining the phylogeny of the rabbiteye blueberry (Vaccinium ashei Reade), the potential fertility levels among its purported diploid ancestral species. Vaccinium atrococcum (Gray) Heller, Vaccinium caesariense MacKenzie, Vaccinium darrowi Camp, and Vaccinium tenellum Ait., were determined. Differences existed among species in female fertility as determined by total number of seeds and number of potentially viable seeds. The number of seeds per berry was lower than that reported for highbush and rabbiteye blueberry cultivars. No differences were found among species in potential male fertility as indicated by percent stainable pollen. Pollen diameter was not a good criterion for distinguishing species or ploidy levels. Comparison of fertility of diploid species with that of purported polyploid derivatives is suggested as a possible aid in determining phylogeny in Vaccinium. Unreduced pollen grains were detected in only 2 of the 4 species in this study. The average return from heterploid (4n × 2n) crosses was 3 seedlings per 1000 pollinations.
Received for publication December 4, 1975. Paper No. 4848 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, N.C. Part of a thesis submitted in partial fulfillment of the Doctor of Philosophy degree, Department of Horticultural Science.
Assistant Professor and Professor, respectively.
Phenotypically almost all highbush blueberry cultivars fall within Camp's (3) circumscription of V. australe, although, for convenience, since most of the cultivars have several species in their ancestry, they are often referred to as V. corymbosum L.