Artificial induction of chromosome-doubled highbush blueberries from pluripotent calli by trifluralin and colchicine

Artificial chromosome doubling of somatic cells enables the production of polyploid plants, which can then be employed in the breeding of novel varieties exhibiting superior traits. To induce polyploids in highbush blueberries (Vaccinium corymbosum), pluripotent calli were regenerated from leaves of a tetraploid southern highbush blueberry cultivar 'Diana', and subsequently treated with trifluralin or colchicine. The chromosome ploidy level of the regenerated shoots was determined using a flow cytometer. The results demonstrated that following the inoculation of leaves onto regeneration medium and subsequent culturing in the dark for 15 d, the application of 2−10 mg/L trifluralin or 200 mg/L colchicine for 2 d could result in the generation of chromosome-doubled plants. Trifluralin was proven to be a more efficacious agent than colchicine. The test showed that 15 octoploids were obtained using trifluralin, while three octoploids were obtained using colchicine, and no chimera occurred. The leaf stomata are enlarged and the density distribution of stomata is reduced in chromosome-doubled plants. In comparison to the tetraploid blueberry, the octoploid plants exhibited thicker stems and larger leaves, more canes, earlier flowering, and an enhanced number of sepals and locules structures. Nevertheless, the chromosome doubling in tetraploid blueberries may result in the formation of dwarf plants, the inhibition of seed maturation, and a reduction in fruit set. In conclusion, a methodology for inducing chromosome-doubled blueberries has been established and characterized by safety, stability, and a minimal likelihood of chimera formation.