Blueberry is a high value fruit crop and there is an increased demand for its cultivation and consumption all over the world. The blueberries are grown in diverse regions with varied weather, soil, biotic and abiotic stress limiting their yield. Interspecific hybridization plays a significant role in broadening the genetic base of blueberries that subsequently helps in developing improved cultivars adapted to specific regions. The genetic diversity for cultivated rabbiteye (RE) (2n=6x=72) blueberries is very narrow. Introgression from wild and other cultivated species would provide beneficial diversity for RE blueberries. Vaccinium elliottii (2n=2x=24) is an early flowering, tall and highly deciduous wild blueberry with small black fruits. Like RE, it is adapted to a wide range of soil types in the southeastern United States. On the other hand, southern highbush is a cultivated tetraploid (2n=4x=48) with high fruit quality but requires intensive soil amendment. To broaden the genetic base of blueberry breeding, interspecific crosses were made between three southern highbush breeding lines and V. elliottii. The success of these crosses was challenging due to strong triploid block from heteroploid crosses. Out of 422 pollination events only 8 triploid seedlings were produced, and their ploidy level was confirmed by flowcytometric analysis. Three seedlings were confirmed to be triploids (3x) however, it is expected that triploids are sterile. Seedlings of the triploids were established in tissue culture and chromosome doubling of these triploid hybrids was carried out to improve their crossing efficiency with cultivated blueberries. The shoots produced through tissue culture were treated with 0.02% colchicine for 48 hours and transferred to woody plant medium (WPM). Synthetic hexaploid hybrids produced from this study will be cross compatible with RE blueberries. These synthetic hexaploid hybrids will bridge the ploidy gap among diploid, tetraploid and hexaploid blueberry species.
