INSTABILITY OF TRANSGENE EXPRESSION IN-FIELD GROWN TOBACCO CARRYING THE CSRL-L GENE FOR SULFONYLUREA HERBICIDE RESISTANCE

In previous greenhouse studies, a transgenic tobacco line carrying the mutant Arabidopsis thaliana acetohydroxyacid synthase gene csr1-1 demonstrated a high level of resistance to the sulfonylurea herbicide chlorsulfuron. In subsequent field trials, hemizygous plants of this line were also resistant, however, up to 59% of homozygous plants were damaged by chlorsulfuron. Damage was correlated with the co-suppression of the csr1-1 transgene and the endogenous tobacco AHAS genes, surA and surB, Co-suppression was triggered by the common agronomic practice of seedling transplantation and therefore could not be predicted from studies performed in growth rooms or greenhouses.