Abstract
Selectable marker (SM) genes have been considered necessary to achieve acceptable rates in the generation of transgenic plants. Genes encoding antibiotic or herbicide resistance are widely used for this purpose. In most cases, once transgenic plants have been regenerated, permanence of SM genes in the plant genome is no longer necessary, and it becomes a matter of public concern. Moreover, the removal of SM genes from transgenic plants could facilitate gene stacking through successive transformations, particularly when the availability of these markers is rather limited for most crop plants. In the genus Citrus, with highly heterozygotic species of long generation cycles, methods implying the segregation and removal of marker transgenes in the progeny are not feasible. Here, we have evaluated the direct production of SM-free citrus plants under non-selective conditions, using a “clean” binary vector carrying only the transgene of interest, and through the recovery of transformants by polymerase chain reaction (PCR) analysis of all regenerated shoots. The response of two different citrus genotypes, Carrizo citrange (intergeneric hybrid of C. sinensis L. Osb. X Poncirus trifoliata L. Raf.) and Pineapple sweet orange (C. sinensis L. Osb.), was evaluated. Our results indicate that, in this system, the competence between transgenic and non-transgenic cells is the main factor determining final transgenic regeneration frequencies. For Carrizo citrange, no transgenic plant could be recovered. For Pineapple sweet orange, marker-free transformation efficiency was 1.7%, paving the way for the viable production of orange transformants carrying only the transgene(s) of interest.
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Acknowledgments
A. Ballester was the recipient of a PhD fellowship provided by the Instituto Nacional de Investigaciones Agrarias (INIA). M. Cervera is the recipient of a “Ramón y Cajal” research contract supported by the Ministerio de Ciencia e Innovación and the European Social Fund. This research was supported by grant AGL2009-08052 from the Ministry of Science and Innovation, Spain.
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Ballester, A., Cervera, M. & Peña, L. Selectable marker-free transgenic orange plants recovered under non-selective conditions and through PCR analysis of all regenerants. Plant Cell Tiss Organ Cult 102, 329–336 (2010). https://doi.org/10.1007/s11240-010-9737-1
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DOI: https://doi.org/10.1007/s11240-010-9737-1