Improved Shoot Organogenesis from Leaf Explants of Highbush Blueberry

Abstract

As part of a program to develop transgenic highbush blueberry ( Vaccinium corymbosum L.) cultivars, studies were conducted to determine optimum conditions for high efficiency shoot regeneration from leaf explants of shoots propagated in vitro. The effects on shoot organogenesis of age of explant source, length of dark treatment, the addition of either thidiazuron (TDZ) at 1 or 5 μ m , or zeatin riboside at 20 μ m to the regeneration medium, and a photosynthetic photon flux ( PPF ) of either 18 ± 5 or 55 ± 5 μmol·m –2 ·s –1 were investigated. A maximum of 13.0, 13.0, 12.6, and 4.6 shoots regenerating per explant for cultivars Duke, Georgiagem, Sierra, and Jersey, respectively, occurred on regeneration medium with zeatin riboside and under a PPF of 55 ± 5 μmol·m –2 ·s –1 . `Duke' regenerated equally well on medium with either zeatin riboside or 1 μ m TDZ, whereas the number of shoots per explant for `Georgiagem' and `Sierra' was significantly higher on zeatin riboside. Regeneration of `Duke', `Jersey', and `Sierra' on zeatin riboside was significantly better under a PPF of 55 ± 5 μmol·m –2 ·s –1 than under 18 ± 5 μmol·m –2 ·s –1 , but the higher PPF inhibited regeneration of `Duke' on 5 μ m TDZ. There were no significant differences in percentage of regeneration or the number of shoots per explant from leaf explants derived from either 1-, 2-, or 3-week-old shoot cultures, or when either 1 week or 2 weeks of darkness preceded light treatments. Chemical names used: 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea (thidiazuron, TDZ); 9-(-β-ribofuranosyl)-6-(4-hydroxy-3-methyl-but-2-enylamino)purine (zeatin riboside).