Agrobacterium pRi [T.sub.L]-DNA rolB and [T.sub.R]-DNA opine genes transferred to the spiny amaranth , a nutraceutical crop

In vitro rhizogenesis occurred with a characteristic pattern typical of transformed roots following explant (internode/leaf) inoculation of Amaranthus spinosus L. with four different wild type Agrobacterium rhizogenes strains. The extent of rhizogenesis varied considerably with the explant type and source, and with the Agrobacterium strains employed; internodal segments performed better than leaves. Of the strains employed for cocultivation, A. rhizogenes LBA 9402 carrying pRi 1855 was the most virulent and infectious, causing hairy root induction in the maximum number of explants regardless of their type. Individual root clones (rhizoclones) were maintained on Murashige and Skoog's basal medium without growth regulators. The physical presence of the rolB gene in the [T.sub.L]-DNA segment of the Ri plasmid of the infecting Agrobacterium in leaf tissues of plants regenerated from selected rhizoclones was confirmed by a positive PCR amplification. The ability of the genetically transformed plants to harbour and express [T.sub.R]-DNA specific opine synthase genes (man2 and ags) was substantiated by PCR and opine assay respectively, demonstrating the production of characteristic opines. Such findings are implicated in the context of pharmaceutical exploitation of transformed root cultures of A. spinosus and also towards protecting this nutraceutically important crop, amaranth, against biotic stress challenges via transgenic manipulations. Key words: Amaranthus spinosus L., Agrobacterium rhizogenes, rhizoclones, PCR amplification, opine assay