The use of phosphomannose-isomerase as a selectable marker to recover transgenic maize plants (Zea mays L.) via Agrobacterium transformation.

A new selectable marker system has been adapted for use in Agrobacterium-mediated transformation of maize. This selection system utilizes the pmi gene encoding for phosphomannose-isomerase that converts mannose-6-phosphate to fructose-6-phosphate. Only transformed cells are capable of utilizing mannose as a carbon source. Agrobacterium-mediated transformation of immature embryos followed by a pre-selection of 10-14 days prior to selection at a level of 1% mannose and 0.5% sucrose led to the recovery of trangenic lines of a frequency of as high as 30% in about 12 weeks. Molecular and genetic analysis showed that selected plants contained the pmi gene and that the gene was transmitted to the progeny in a Mendelian fashion.