Tissue culture and Agrobacterium-mediated transformation of watercress

Adventitious shoot regeneration could be obtained from more than 80% of the calluses initiated from stem explants of watercress (Rorippa nasturtium-aq uaticum) by using an induction medium and a shoot regeneration medium. The induction medium contained 1.15 mu M 2,4-dichlorophenoxyacetic acid and 5 m u M thidiazuron; the shoot regeneration medium was composed of 0.5 mu M thi diazuron and 2.25 mu M 6-benzylaminopurine. This regeneration procedure was incorporated into an Agrobacterium-mediated transformation procedure for g ene transfer into watercress. Factors affecting transformation included pre culture, selection agents, use of tobacco nurse cells, and the length of co culture. A transgenic line of watercress transformed with a wild-type Bacil lus thuringiensis insecticidal gene, cry1Ia3, was not toxic to larvae of th e diamondback moth (Plutella xylostella), presumably due to premature polya denylation of the transcript encoded by this gene in the plant.