Agrobacterium-mediated genetic transformation and regeneration of transgenic plants from cotyledon explants of groundnut (Arachis hypogaea L.) via somatic embryogenesis

An efficient transformation protocol was developed for groundnut (Arachis h ypognea L.) plants. Precultured cotyledons were co-cultured with Agrobacter ium tumefaciens strain LBA 4404 harbouring the binary vector pBI121 contain ing the uidA (GUS) and nptII genes for 2 days and cultured on an embryo ind uction medium containing 0.5 mg/l NAA, 5.0 mg/l BAP, 75 mu g/ml kanamycin a nd 300 mu g/ml cefotaxime. The putatively transformed embryos were transfer red to the medium with reduced kanamycin (50 mu g/ml) for further developme nt. Prolific shoots developed from these embryos on a MS medium containing 0.5 mg/l BAP and 50 mu g/ml kanamycin with a transformation efficiency of 4 7%. The elongated kanamycin-resistant shoots were subsequently rooted on th e MS medium supplemented with 1.0 mg/l IBA. The transgenic plants were late r established in plastic cups, A strong GUS activity was detected in the pu tatively transformed plants by histochemical assay. Transformation was conf irmed by PCR analyses. Integration of T-DNA into nuclear genome of transgen ic plants was further confirmed by Southern hybridization with nptII gene p robe. A large number of transgenic plants were obtained in this study. This protocol allows effective transformation and quick regeneration via embryo genesis.