Phosphomannose-isomerase (pmi) gene as a selectable marker for rice transformation via Agrobacterium

A new selectable marker system was adapted for use in Agrobacterium-mediated transformation of rice (Oryza sativa L.). This selection system utilizes the pmi gene encoding for phosphomannose-isomerase that converts mannose-6-phosphate to fructose-6-phosphate. Only transformed cells were capable of utilizing mannose as a carbon source. Transgenic rice plants regenerated from selected transformed immature embryo-derived calli on media containing various concentrations of mannose. The highest transformation frequency of 6.0% was obtained when a combination of 25 g/l mannose and 5 g/l sucrose was used. Molecular and genetic analyses showed that the plants contained the pmi gene and the gene was transmitted to the progeny in Mendelian fashion. The results indicated that the mannose selection system, which was devoid of the disadvantages of antibiotic or herbicide selection, could be used for rice Agrobacterium-mediated immature embryo transformation. (C) 2003 Elsevier Ireland Ltd. All rights reserved.