Tribenuron-methyl resistance and mutation diversity of Pro197 in flixweed (Descurainia Sophia L.) accessions from China.

Flixweed (Descurainia Sophia L.) is a problematic weed in winter wheat fields in China, which causes great loss of wheat yield. A total of 46 flixweed accessions from winter wheat-planting areas were collected and used for the survey of resistance to tribenuron-methyl and Pro197 mutation diversity. According to the "R" resistance rating system, 16 flixweed accessions have evolved resistance to tribenuron-methyl, 13 accessions have high risk of developing resistance to this herbicide and 17 accessions are susceptible. The mutation of Pro197 codon (CCT) changed proline (Pro) into leucine (Leu) (homozygous, RR), serine (Ser, RR), histidine (His, RR), threonine (Thr, RR), Pro/Leu (heterozygous, RS), Pro/Ser (RS), Pro/His, Pro/Thr (RS) and Pro/Tyr (RS). Among these amino acid changes, a Pro197-Pro/Tyr (heterozygous, RS) substitution caused by the mutation of two successive nucleotides was identified for the first time in resistant weed species. In addition, the Pro197-His and Pro197-Pro/His mutations have not been reported previously in flixweed. Finally, a CPAS marker was developed to identify flixweed plants with or without Pro197 mutation.