Somaclonal variation in watercress for resistance to crook root disease.

Watercress (Rorippa nasturtium-aquaticum) shoots were regenerated from callus initiated from petioles on a range of media. The best coefficient of regeneration was obtained when callus was induced on a medium containing 0.25 mgl(-1) thidiazuron and 0.05 mgl{si-1} 2,4-D, followed by regeneration on 0.25 mgl(-1) thidiazuron. Plants were then screened for resistance to crook root disease of watercress in a laboratory screening test which revealed significant somaclonal variation between the controls and some of the somaclones.