Co-transformation of indica rice protoplasts with gusA and neo genes.

Protoplasts of the indica rice (Oryza sativa L.) variety, IR54, were transiently transformed with the gusA gene and stably transformed with both the neo and gusA genes. We show that PEG-mediated co-transformation of protoplasts with two genes on separate plasmids coupled with selection on kanamycin is an effective way of transferring foreign gene(s) into the indica rice genome. The efficiency of co-transformation was generally 20-30%, i.e. the frequency of kanamycin-resistant calli having both the neo and gusA active genes. Southern blot analysis using a probe for gusA indicated integration of several copies of the gene, often as head to tail tandem repeats.