Recent Advances in Blueberry Transformation

Abstract

Although Vaccinium cultivars have been generated exclusively through the traditional methods of controlled hybridization and deliberate selection, genetic transformation could provide a powerful approach to supplement conventional breeding methods for Vaccinium by introducing genes of interest. A reliable transformation system depends on efficient plant regeneration, reliable gene delivery, and effective selection. To date, in blueberry, adventitious shoot regeneration using leaf explants has been the most desirable regeneration system; Agrobacterium-mediated transformation is the major gene delivery method; and effective selection has been reported using either the nptII or the bar gene as selectable markers. In 2004, stable transformation was reported for four highbush blueberry cultivars, with a transformation frequency ranging from 5.0–15.3%. In 2006, the first field trial of transgenic blueberry with herbicide resistance was performed. In 2009, a blueberry C-repeat binding factor (CBF) gene (GenBank AF234316) was transformed into a southern highbush blueberry cultivar Legacy in order to improve cold tolerance by elucidating the CBF-regulated network in blueberry. This progress has demonstrated that blueberries can be improved through genetic engineering. In the future, as more genomic resources for Vaccinium become available, more genes of interest will be identified and isolated. Genetic transformation will allow us to evaluate these genes as to their functions. Currently, there is industry-wide concern about the application of transformation technology in blueberries, even though numerous transgenic crops have been deployed. Hopefully, new engineering strategies, such as intragenic transformation, RNAi, and marker-free technologies, will reduce public concerns about transgenic Vaccinium plants.