TRANSFORMATION AND REGENERATION OF ENGLISH ELM USING WILD-TYPE AGROBACTERIUM-TUMEFACIENS

In vitro proliferating shoots of a clone of the English elm, Ulmus pro cera SR4, were infected with the wild-type Agrobacterium tumefaciens s train 82.139 under a variety of conditions. A co-cultivation medium of pH 5.2 was found to be optimal for infection by uninduced A. tumefaci ens 82.139, with 70-75% of inoculated shoots forming tumours. In the p resence of 0.1 mM acetosyringone (a virulence inducing agent), the hig hest percentage tumour formation was obtained following co-cultivation at pH 5.8. The tumours were brown to white in colour, and were able t o regenerate shoots capable of independent growth. Some of these shoot s proved to be transformed with the T-DNA of A. tumefaciens 82.139 on the basis of nopaline production and Southern hybridisation. These res ults are discussed in relation to the development of a transformation protocol using disarmed agrobacteria harbouring manipulated Ti plasmid s.