Development of marker-free transgenic sorghum [Sorghum bicolor (L.) Moench] using standard binary vectors with bar as a selectable marker
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We report an Agrobacterium-mediated transformation system that can generate marker-free transgenic sorghum [Sorghum bicolor (L.) Moench] from a public line [P898012] using standard binary vectors with bar as a selectable marker. Eight co-cultivation conditions were examined for their effect on transformation. The average transformation frequencies were 0.4 and 0.7% for pZY101-TC2 and pZY101-SKRS, respectively, derived from binary vector pZY102 and containing bar and target gene(s) in separate T-DNA regions. A low selection pressure (2.5 mg l−1 DL-phosphinothrithin, PPT) was deployed during callus induction in combination with rapid selection to generate plants from 80 independent events, all but three of which were fertile and set seed. PCR and Southern analyses showed that 36 out of 80 events contained both bar and the target gene(s) (an average co-transformation frequency of 45%). Seedlings of the T1 generation transmitted T-DNAs with target gene(s) and bar gene independently, generating a fraction of progeny with only the target gene(s).
KeywordsSorghum bicolor Agrobacterium bar Binary vector Marker-free Transformation
The authors thank: Scanlon S and other colleagues from Dr. Folk’s lab for their assistance; Z. Zhao, N. Wang, S. Zheng and H. Cline (Pioneer Hi-Bred Intl. Inc.) for helpful suggestions and for P898012 and Drs. G. Liang and Z. S. Gao (Kansas State University) for helpful comments; Aventis CropScience (Research Triangle Park, NC) for providing glufosinate-ammonium and Liberty® as generous gifts; Dr. Seth D. Findley (University of Missouri, Columbia, MO) for critical review of the manuscript. All sorghum transformation experiments were conducted in the Plant Transformation Core Facility at the University of Missouri. Financial support was provided by the University of Missouri Agricultural Experiment Station, the Provost’s office and the University of Missouri Food for the twenty-first Century Eminence Program.
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