A method for early detection of T-DNA transfer

A mannopine synthase—β-glucuronidase gene fusion,mas-uidA, was used to detect T-DNA transfer 48 hours afterA. tumefaciens infection of radish root disks. A detailed procedure for infection, tissue preparation and GUS histochemistry is given. A CaMV 35S promoter was shown to be unsuitable as it was highly expressed in the bacteria. A distinct pattern of GUS activity was found in radish roots infected with themas-uidA fusion indicating a specificity of expression in the metabolically active cambium and phloem parenchyma cells. This assay is useful for studying T-DNA transfer and host range differences amongA. tumefaciens strains.