Transgenic indica rice (Oryza sativa L.) plants from microprojectile bombardment of embryogenic cell clusters

A reproducible transformation system for an improved indica rice was developed based on particle inflow gun-mediated plasmid DNA delivery into embryogenic cell clusters. A chimeric beta-glucoronidase (gus A) gene construct was used to optimize the transient expression. For stable transformation, two constructs both containing a chimeric hygromycin phosphotransferase (hph) gene were separately introduced into the cells of embryogenic cells clusters. Placing embryogenic cell clusters on high maltose containing medium before, during and after bombardment significantly increased the transient and stable transformation events. Resistant calli were readily recovered from hygromycin containing medium. Transgenic (To) plants were routinely regenerated from calli resistant to hygromycin B. The presence of the hph gene in the To plants was demonstrated by Southern blot analysis. Mendelian inheritance of the hygromycin trait was demonstrated in T-2 generation.