Absorption, translocation, and metabolism of florpyrauxifen-benzyl and cyhalofop-butyl in cyhalofop-butyl-resistant barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.]

Metabolic cross-resistance to florpyrauxifen-benzyl in barnyardgrass (Echinochloa crus-galli) evolved before the commercialization of Rinskor™

“…In the winter following the commercial launch of florpyrauxifen-benzyl, a greenhouse screen performed across multiple E. crus-galli populations from the midsouthern United States identified populations with resistance to florpyrauxifen-benzyl (Hwang et al 2022b;Miller et al 2018). A follow-up study associated the resistance mechanism to reduced foliar absorption and decreased activation of florpyrauxifen-benzyl into its acid form in resistant plants (Hwang et al 2022a(Hwang et al , 2022b. The same study found no mutations in the auxin receptors TIR1 and AFB5, although most cases of target-site resistance to synthetic auxins are associated with the Aux/IAA co-receptor proteins (Figueiredo et al 2022;Todd et al 2020).…”

Metabolic Exploration for Cyhalofop-Butyl Antagonism in Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] Following Pretreatment of Malathion

“…Although the tested R barnyardgrass biotypes were verified with no mutation to ACCase -encoding genes through DNA sequence analysis in the previous study, there is still a potential that Sanger sequencing can miss mutations in specific loci during actual synthesis of the protein following herbicide treatment . Seven codons of ACCase genes in barnyardgrass, including Ile1781, Trp1999, Trp2027, Ile2041, Asp2078, Cys2088, and Gly2096, are known as target-sites of ACCase-inhibiting herbicides. − There have been some reports that the mutation observed in single locus or multiple loci of ACCase genes can contribute to conferring the CyB resistance to weed species. , However, in the present study, RNA sequence analysis results for each locus of ACCase gene showed high sequence identity of >92% among S and R biotypes within the target-sites.…”

“…Resistant (R) barnyardgrass biotypes used in the present study were two (R1 and R2) of three biotypes revealed with resistance to both CyB (R/S ratios = 7 and 21, respectively) and florpyrauxifen-benzyl (R/S ratios = 50 and 150, respectively) in a previous study . Seeds of R1 and R2 barnyardgrass biotypes were collected from midsouthern USA rice fields where herbicides failed to provide satisfactory controls of the weed, by consultants and producers in 2019.…”

“…Resistant (R) barnyardgrass biotypes used in the present study were two (R1 and R2) of three biotypes revealed with resistance to both CyB (R/S ratios = 7 and 21, respectively) and florpyrauxifen-benzyl (R/S ratios = 50 and 150, respectively) in a previous study. 34 Seeds of R1 and R2 barnyardgrass biotypes were collected from midsouthern USA rice fields where herbicides failed to provide satisfactory controls of the weed, by consultants and producers in 2019. From the resistance screening test with seven herbicides including CyB (313 g ai ha −1 ; Clincher SF, Corteva Agriscience), florpyrauxifen-benzyl (30 g ai ha −1 ; Loyant, Corteva Agriscience, IN, USA), quinclorac (560 g ai h −1 ; Facet L, BASF, NJ, USA), propanil (4480 g ai ha −1 ; Propanil 4SC, Generic Crop Science, NV, USA), clomazone (336 g ai ha −1 ; Command 3ME, FMC, PA, USA), imazethapyr-ammonium (70 g ai ha −1 ; Newpath, BASF), and glyphosate-potassium (434 g ai ha −1 ; Roundup PowerMax, Bayer Cropscience, MO, USA), the R biotypes were verified to be resistant to CyB and florpyraxifen-benzyl.…”

“…In our previous study, 34 barnyardgrass biotypes with multiple resistance to CyB and a synthetic auxin herbicide florpyrauxifen-benzyl were confirmed and explored to reveal the herbicide resistance mechanisms. However, in that study, the mechanism study of CyB resistance was left as a further study due to a difficulty in analyzing specific metabolites of CyB with radioisotopes.…”