Production of terpenes by differentiated shoot cultures of Mentha citrata transformed with Agrobacterium tumefaciens T37.

Crown gall initiation on Mentha × piperita var. citrata (Ehrh.) Briq. (mint) was investigated using a range of wild type and mutant strains of Agrobacterium tumefaciens. Axenic transformed shoot cultures of Mentha 'citrata' were established on plant stems inoculated with the nopaline strain T37 of Agrobacterium tumefaciens. The presence of T-DNA in the transformed tissues and the absence of bacterial contamination was established by Southern Blot hybridisation, using (32)P labelled fragments of the T-DNA and virulence region of the Ti plasmid as probes. The shoot cultures synthesised a mint oil fraction which contained the major terpenes characteristic of the parent plant in quantities similar to those found in intact tissue. Oil glands were observed to be present on the leaves of the transformed culture using scanning electron microscopy.