Green fluorescent protein as a visual selection marker for papaya (Carica papaya L.) transformation.

Chemical-based selection for plant transformation is associated with a number of real and perceived problems that might be avoided through visual selection. We have used green fluorescent protein (GFP), as a visual selectable marker to produce transformed papaya ( Carica papaya) plants following microprojectile bombardment of embryogenic callus. GFP selection reduced the selection time from 3 months on a geneticin (G418) antibiotic-containing medium to 3-4 weeks. Moreover, GFP selection increased the number of transformed papaya plants by five-to eightfold compared to selection in the presence of antibiotics. Overall, the use of GFP for selecting transgenic papaya lines improved our throughput for transformation by 15- to 24-fold while avoiding the drawbacks associated with the use of antibiotic resistance-based selection markers.