DEVELOPMENT AND EVALUATION OF A LABORATORY-BASED TECHNIQUE FOR SCREENING SOMACLONAL REGENERANTS OF WATERCRESS (RORIPPA-NASTURTIUM-AQUATIUM)FOR RESISTANCE TO CROOK ROOT DISEASE (SPONGOSPORA-SUBTERRANEA F-SP NASTURTII)

A laboratory based method has been developed for infecting watercress with the crook root fungus (Spongospora subterranea f.sp. nasturtii). This utilised plastic trays of nutrient solution on which watercress s hoots, supported by floats, were grown for a pre-inoculation period of 14 days before an inoculum consisting of 1 g of crook roots was added . Seven watercress somaclones derived from plantlets regenerated from callus of a parental commercial control line (clone A) were tested on three separate occasions. No variation within the parental control pla nts was seen but significant variation both between and within the ind ividual somaclones over successive tests was observed. Two somaclones showed increased resistance to crook root disease compared with parent al control plants.