Transformation of Indica Rice (<italic>Oryza sativa</italic> L.) Mediated by <italic>Agrobacterium tumefaciens</italic>

Abstract

A system has been developed for the transfer of genes by Agrobacterium tumefaciens to indica rice (Oryza sativa L. cv. Taichung Native 1), and optimal conditions for such Agrobacterium-mediated transformation have been determined. Excised stems, leaves, and roots from 3- to 4-day-old seedlings were infected with strains of Agrobacterium that carried plasmids with chimeric derivatives of genes for β-glucuronidase (GUS) and neomycin phosphotransferase (NPTII). After selection with the antibiotic G418, only roots survived and formed calli. The integration of chimeric genes in the rice genome was demonstrated by Southern analysis and assays of enzymatic activity. We obtained a transformation frequency of 37.5% for transgenic callus. In addition, the absence of hybridization with vir probes indicated that transformants were not contaminated with Agrobacterium. The complete failure of transformation in the absence of medium from potato suspension cultures (PSC) indicates that PSC is essential for Ti-mediated transformation in indica rice. A high efficiency of transformation was observed upon infection with the cointegrate vector pGV2260::NG1.