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Background Conventional crossing of soft wheat cultivars resistant to imazamox and glufosinate resulted in two (Rados and Helter) lines resistant to both herbicides. Stacked traits conferring this dual herbicide resistance in these lines, compared with a susceptible (S) cultivar, were characterized. Results Rados and Helter lines were ∼ 18-fold more resistant (R) to glufosinate, and between 15.1 and 19.8-fold more resistant to imazamox than the S cultivar. Resistance to glufosinate and imazamox decreased up to 12% and 50%, respectively, when the herbicides were applied sequentially. The basal activities of the acetolactate and glutamine synthases were similar between R and S plants. Rados and Helter lines were 11.7- and 17.7-fold more resistant to imazamox than the S cultivar, due to the Ser653-Asn mutation in their imi-ALS genes. R lines, susceptible to glufosinate at the target site level, showed lower ammonia accumulation evidencing the activity of the phosphinothricin acetyl transferase. Absorption and translocation patterns for 14 C-imazamox and 14 C-glufosinate were similar between R and S cultivars and so do not contribute to resistance. Conclusion Stacked traits conferring dual herbicide resistance to the lines Rados and Helter come from the resistant parents. These R lines are potential tools for weed management in wheat production, mainly via herbicide rotation. © 2018 Society of Chemical Industry.

BACKGROUND Susceptibility and the mechanism (s) governing tolerance/resistance to glyphosate were characterized in two putative-glyphosate-resistant Chloris barbata populations (R1 and R2), collected in Persian lime orchards from Colima State, Mexico, comparing them with one non-treated population (referred to as S). RESULTS Glyphosate doses required to reduce fresh weight or cause mortality by 50% were 4.2–6.4 times higher in resistant populations than in the S population. The S population accumulated 4.3 and 5.2 times more shikimate than the R2 and R1 populations, respectively. There were no differences in 14C-glyphosate uptake between R and S populations, but the R plants translocated at least 12% less herbicide to the rest of plant and roots 96 h after treatment. Insignificant amounts of glyphosate were metabolized to aminomethyl phosphonate and glyoxylate in both R and S plants. The 5-enolpyruvylshikimate-3-phosphate synthase gene of the R populations contained the Pro106-Ser mutation, giving them a resistance 12 (R2) and 14.7 (R1) times greater at target-site level compared with the S population. CONCLUSION The Pro106-Ser mutation governs the resistance to glyphosate of the R1 and R2 C barbata populations, but the impaired translocation could contribute to the resistance. These results confirm the first case of glyphosate resistance evolved in this species. © 2018 Society of Chemical Industry