Functional synergy and genomic linkage of glyphosate resistance traits in Canada fleabane.

Background: Glyphosate resistance in Conyza canadensis (Canada fleabane) has been primarily attributed to non-target-site resistance (NTSR) mechanisms such as vacuolar sequestration, though these have not been formally elucidated. While a target-site mutation at EPSPS2 (P106S) was recently identified, it failed to account for many resistant cases. These findings underscore the need to re-evaluate the genetic basis of glyphosate resistance in this species.

Target-site EPSPS Pro-106-Ser mutation in Conyza canadensis biotypes with extreme resistance to glyphosate in Ohio and Iowa, USA.

Documenting the diversity of mechanisms for herbicide resistance in agricultural weeds is helpful for understanding evolutionary processes that contribute to weed management problems. More than 40 species have evolved resistance to glyphosate, and at least 13 species have a target-site mutation at position 106 of EPSPS. In horseweed (Conyza canadensis), this p106 mutation has only been reported in Canada.