CHLORSULFURON RESISTANCE IN DAUCUS-CAROTA CELL-LINES AND PLANTS - INVOLVEMENT OF GENE AMPLIFICATION

Daucus carota L. cell lines stably resistant to the herbicide chlorsul furon (CS) have been isolated according to a stepwise selection. Studi es carried out during different selection steps show that the specific activity of the target enzyme acetohydroxyacid synthase (AHAS) increa ses along with CS resistance. Southern hybridization analysis performe d with a Brassica napus AHAS probe in a CS highly-resistant cell line reveals the presence of a greatly amplified EcoRI fragment of genomic DNA. This indicates that AHAS overproduction induced by stepwise selec tion is due to gene amplification. Regenerants from some resistant cel l lines maintained the CS-resistant trait at the whole plant level.