Molecular basis of blackgrass (Alopecurus myosuroides HUDS.) resistance to sulfonylurea herbicides

Abstract

Blackgrass biotype resistant to the mesosulfuron + iodosulfuron mixture has been found in Poland and was investigated in this study. Seedlings that survived double-dosed herbicide treatment were submitted to molecular analysis in order to explain the mechanism of resistance. Domains A and B of the acetolactate synthase gene were amplified by PCR and then sequenced. Biotypes which were both resistant and susceptible to mesosulfuron+iodosulfuron were analyzed. The comparison of the obtained sequences was made on a nucleotide and aminoacid level. The comparison revealed a substitution of proline codon to histidine codon in position 197 in each resistant plant. Mutation Pro197His is the basis of the target site resistance of A. myosuroides to sulfonylureas. There were no other mutations in als gene of the biotype that might modify the level of resistance to these herbicides.