Hybridization of Cultivated Highbush Blueberry with Vaccinium stamineum: Phenotype and Fertility of Backcross1 Populations

Abstract

<jats:p>Nine F<jats:sub>1</jats:sub> hybrids produced by crossing seven tetraploid highbush blueberry cultivars with three tetraploid <jats:italic>Vaccinium stamineum</jats:italic> genotypes were backcrossed to an array of highbush blueberry cultivars to produce 2500 Backcross<jats:sub>1</jats:sub> (BC<jats:sub>1</jats:sub>) seedlings. Thirty of the most vigorous BC<jats:sub>1</jats:sub> plants were intercrossed in a greenhouse. Fertility of the BC<jats:sub>1</jats:sub> plants was studied by examining their pollen at 250× and by determining the number of well-developed seeds per pollinated flower after the crosses. Percent well-formed microspores averaged 62.7% for BC<jats:sub>1</jats:sub> plants compared with 30.9% for their F<jats:sub>1</jats:sub> hybrid parents. Fruit set percentage was high from the BC<jats:sub>1</jats:sub> intercrosses, with an average of 9.29 plump seeds per pollinated flower. The 2500 BC<jats:sub>1</jats:sub> seedlings in the field were highly variable in vigor, but fewer than 10% were as vigorous as the median vigor of highbush × highbush seedlings. BC<jats:sub>1</jats:sub> plants in the field averaged ≈1 month later ripening than highbush × highbush seedlings and berries averaged slightly smaller. Berry clusters were very loose compared with those of highbush. Berry flavor was highly variable from plant to plant, but the berries averaged less sweet and lower in acid than highbush berries. New flavor components not found in highbush seedlings were found in only a few BC<jats:sub>1</jats:sub> seedlings. Fresh berries from BC<jats:sub>1</jats:sub> plants made bright red juice when crushed in water, whereas berries from most highbush cultivars produced brown to yellow juice/water mixes. Although berry quality in the BC<jats:sub>1</jats:sub> population averaged lower than in highbush seedlings, some plants had berry quality as high as typical cultivars. Because <jats:italic>V. stamineum</jats:italic> is highly drought-tolerant, cultivars bred using <jats:italic>V. stamineum</jats:italic> introgression could have improved upland adaptation.</jats:p>

Genomic and evolutionary relationships among wild and cultivated blueberry species

“…Southern blueberry species represent a rich genetic resource for selecting accessions with valuable horticultural traits [ 34 ]. Admixed populations resulting from the wide hybridization of V. darrowii and V. myrsinites are evergreen xerophytic, fire-adapted plants [ 4 , 7 , 8 ] and occupy wide ranges [ 5 ]. V. myrsinites is probably an autotetraploid of V. darrowii, and thus other than chromosome counts or hybridization experiments, grey glaucescence on new growth flushes, and fruit of V. darrowii can be used to separate the two species.…”

“…Commercial blueberry varieties have also been derivatives of wide hybridization for developing homoploid hybrids with desirable traits. Recently developed hybrids are the result of a cross between domestic cultivars and wild species to attribute a wider genetic variance to these plants with hopes for plants to inherit superior traits [ 8 ]. Heteroploid crosses are partially fertile, which offers the possibility of introgression into cultivated germplasm.…”

“…Vaccinium species from the Cyanococcus section are widespread throughout eastern North America, striving in diverse environments, thus widening the genetic divergence among the species [ 5 , 24 ]. Wild species in the neotropics and subtropics generally tolerate heat and drought [ 8 ]. These wild species could be a repository of favorable alleles for future use in introgression programs.…”

Breeding Cultivars from Blueberry × Deerberry Hybrids: Progress and Prospects

“…Tetraploid hybrids between highbush blueberry cultivars and colchicine-induced tetraploid V. stamineum have been reported previously (Lyrene, 2016(Lyrene, , 2018. This article describes further progress in our efforts to recombine the genes of highbush cultivars and V. stamineum.…”