Hybridization and introgression between deerberries and blueberries: Problems and progress

Several hundred F1 Vaccinium intersectional hybrids were produced between sections Cyanococcus and Polycodium. Tetraploid highbush blueberry cultivars (section Cyanococcus hybrids based on V. corymbosum) were the seed parents and colchicine-induced tetraploids of tall-growing (2-5m) deerberry plants (Vaccinium stamineum) from north-central Florida served as the pollen parents. Nine selected F1 hybrids were backcrossed to highbush cultivars, and more than 2,000 of the resulting BC1 seedlings were evaluated in field nurseries. Fifty-seven of the most vigorous BC1 seedlings were selected. Some were transplanted to 20-liter pots, others to a field with drip irrigation at 1 m x 3 m spacing. All were evaluated a year later for plant and berry characteristics after open pollination. BC1 plant architecture was similar to that of highbush, but most plants were less vigorous. Flowers on many plants had short corollas and exserted stigmas, making pollen, stigmas, and nectar more accessible to honeybees than they are in highbush cultivars. Plants flowered heavily, and fruit set was as high as is typical in commercial fields of highbush cultivars; almost every flower made a berry. Berries were fully seeded. Berries ripened 2 to 4 weeks later than highbush, were as large as highbush berries, and had green-white pulp and medium to high firmness. Berries on most BC1 plants had black, somewhat tough skins, but berries on some selections were glaucous. Stemminess varied from near zero to 30%, with low to medium berry shattering. Picking scars ranged from small to large. Berry flavor averaged lower than in highbush. The main drawback with flavor was low sugar. Some clones had aromatic flavor components, not always pleasant. Berries on a few plants were near cultivar quality. Possible benefits from V. stamineum introgression include flowers with short, open, corollas (which could facilitate pollination and increase fruit set), red to purple berry pulp, (seen in some F1 but no BC1 plants), open flower clusters, and increased drought tolerance