Genetic transformation of the commercial barley (Hordeum vulgare L.) cultivar Conlon by particle bombardment of callus

Commercial barley cultivars are difficult to transform because of the lack of an efficient regeneration system. By modifying certain components in the standard culture medium, we have developed a reproducible and more efficient regeneration system. Herbicide-resistant transgenic plants from barley (Hordeum vulgare L. cv. Conlon) were obtained using this medium. Embryo-derived callus was bombarded with pAHC25, which contains the screenable marker gus (#-glucuronidase) and the selectable marker bar (bialaphos resistance gene), both driven by the maize ubiquitin promoter (Ubi1) and followed by the nos terminator. Following bombardment, callus was transferred to callus-induction medium supplemented with 5 mg/l bialaphos for selection. Resistant calli were subsequently transferred to maintenance medium containing 5 mg/l bialaphos for further selection and finally transferred to regeneration medium with 5 mg/l bialaphos. Green shoots that developed on the regeneration medium were transferred to rooting medium containing 3 mg/l bialaphos. Eighty-five transgenic plants were obtained from 13 independent transformation events. Progeny tests showed Mendelian inheritance for the transgenes. This is the first report of the production of large numbers of transgenic plants from a commercial cultivar adapted to Midwestern US barley production.