Plant regeneration from transformed embryogenic callus of an elite indica rice via Agrobacterium

Abstract

The present study describes a simple and efficient protocol for plant regeneration from scutellar-derived embryogenic calli of an elite basmati indica rice (Oryza sativa L., cv Pusa Basmati 1) transformed with Agrobacterium. A supervirulent plasmid pTOK233 as well as a non-supervirulent plasmid pJB90GI containing β-glucuronidase (gus) and hygromycin phosphotransferase (hpt) chimeric genes were used to assess transformation and regeneration efficiency. The effects of some factors like the bacterial density and inclusion of sorbitol in the medium on the co-culture and transformation have been evaluated; the procedure for selection and regeneration from transformed calli was found to be critical. Furthermore, co-culture and selection on regeneration medium was found to be better than callus medium and led to minimal media manipulations. Regeneration medium supplemented with 3% maltose was found to be better for regeneration as compared to 3% sucrose. The transformed calli were subjected to three cycles of regeneration, thus converting a higher number of transformation events into regenerants. The selected calli as well as leaf sections and roots of the transformants were GUS positive. The stable integration of the transgene was confirmed by polymerase chain reaction and Southern blot analysis of the transformants. Interestingly, the presence of three additional vir genes in supervirulent plasmid pTOK233 was not required for transformation as transformation was successful with non-supervirulent plasmid pJB90GI, although the transformation and regeneration frequency was higher with the former. This effective protocol for regeneration from transformed calli resulted in a relatively high transformation frequency.