Non‐target‐site resistance mechanism of barnyardgrass [<scp><i>Echinochloa crus‐galli</i></scp> (L.) P. Beauv.] to florpyrauxifen‐benzyl
Jeong‐In Hwang, Jason K. Norsworthy, Fidel González‐Torralva, Grant L. Priess, L. Tom Barber, Thomas R. Butts
Abstract
Abstract BACKGROUND Florpyrauxifen‐benzyl (FPB) is an arylpicolinate herbicide (Group IV) for barnyardgrass control in rice. One susceptible (Sus) and three putative FPB‐resistant (R1, R2, and R3) barnyardgrass biotypes were selected based on resistant/susceptible (R/S) ratios obtained from dose–response tests and used to investigate the potential resistance mechanisms. RESULTS Based on visual control results, the R/S ratios of barnyardgrass biotypes R1, R2, and R3 were 60‐, 33‐, and 16‐fold greater than the Sus standard, respectively. Sequencing results of TIR1 and AFB genes in the tested barnyardgrass revealed no difference between Sus and R barnyardgrass biotypes. Absorption of [ 14 C]‐FPB in Sus barnyardgrass increased over time and reached 90%, which was >10 percentage points greater than that in R biotypes. The [ 14 C]‐FPB absorption in all R barnyardgrass equilibrated after 48 h. For both Sus and R barnyardgrass, most [ 14 C]‐FPB absorbed was present in the treated leaf (79.8–88.8%), followed by untreated aboveground (9.5–18.6%) and belowground tissues (1.3–2.2%). No differences in translocation were observed. Differences between Sus and R barnyardgrass biotypes were found for FPB metabolism. Production of the active metabolite, florpyrauxifen‐acid, was greater in Sus barnyardgrass (21.5–52.1%) than in R barnyardgrass (5.5–34.9%). CONCLUSION In conclusion, reductions in FPB absorption and florpyrauxifen‐acid production may contribute to the inability to control barnyardgrass with FPB. © 2021 Society of Chemical Industry.