Abstract
In order to improve elm resistance to dutch elm disease by genetic engineering, woody internodes of field grown elms Commelin were tested for regeneration capacity and susceptibility to
Agrobacterium tumefaciens. After a drastic surface disinfection (especially burning), the explants were introduced in vitro on a medium containing cef otaxime (500 mg - L
∔1). Budding took place within 2 weeks on the cambial part of the explants. After 1-2 months, the number of rootable shoots per explant was 3 -6, increasing up to 13 by shoot excision. Shoot rooting (70 %) and acclimatization (survival 80 %) were easy.
Agrobacterium tumefaciens wild strains (Ach5, T37, C58, 82-139) were either inoculated on shoots or cocultivated on internodes. Octopine/agropine type Ach5 induced tumors (> 50 %) where agropine was often detected. Efficiency of 82-139 was lower. However, it was very effective in improving budding ability of internodes up to 11. A strategy to obtain transgenic elm based on these results is now in progress.