Mechanism of herbicidal activity of a new cyclohexane‐1,3‐dione, tepraloxydim to Poa annua L.

Abstract

Tepraloxydim [(EZ)‐(RS)‐2‐{1‐[(2E)‐3‐chloroallyloxyimino]propyl}‐3‐hydroxy‐5‐perhydropyran‐4‐ylcyclohex‐2‐en‐1‐one] showed high activity against annual bluegrass (Poa annua L.), which is relatively tolerant to sethoxydim [(±)‐2‐(1‐ethoxyiminobutyl)‐5‐[2‐(ethylthio)propyl]‐3‐hydroxycyclohex‐2‐en‐1‐one]. Absorption and translocation rates of tepraloxydim and sethoxydim were higher in P. annua than in Setaria faberi, but the absorption and translocation patterns of tepraloxydim in the two plants were similar to those of sethoxydim. Metabolic rates of tepraloxydim and sethoxydim in P. annua and S. faberi were found to be similar. The concentration for 50% inhibition (I50) of acetyl‐coenzyme A carboxylase (ACCase) with tepraloxydim was approximately 3 × 10−6 mol L−1 for P. annua and 7 × 10−7 mol L−1 for S. faberi. For sethoxydim, the I50 was found to be 2 × 10−6 mol L−1 with the enzyme of S. faberi, while sethoxydim showed a slight effect on ACCase from P. annua activity, even at 10−4 mol L−1. The strong inhibition of ACCase with tepraloxydim is considered to be the major factor contributing to the high herbicidal activity against P. annua. Measuring the whole plant growth response, the ratio of the tepraloxydim I50 dose of P. annua to that of S. faberi (P/S) was found to be 2.4, while the P/S ratio of sethoxydim and a tepraloxydim analog with a propyl chain at R2 were 56.3 and 73.3, respectively. The herbicidal activity against P. annua was remarkably influenced by the length of the R2 alkyl chain, while the effect on S. faberi was not affected. Acetyl‐coenzyme A carboxylase from P. annua also exhibited a higher resistance to the tepraloxydim analog with a propyl chain than to tepraloxydim. These results suggest that a binding site structure of cyclohexane‐1,3‐diones in the ACCase differs between P. annua and S. faberi.

Incidence of multiple herbicide resistance in annual bluegrass (Poa annua) across southeastern Australia

“…Poa annua is normally considered to be tolerant to Group 1 herbicides (Herbert et al 1997); however, some herbicides in this group can provide control (Takahashi et al 2002). The S population was controlled with 60 g ha −1 pinoxaden in our experiments showing it was susceptible to pinoxaden ( Figure 2C).…”

A different mechanism for the inhibition of the carboxyltransferase domain of acetyl-coenzyme A carboxylase by tepraloxydim

“…1A), are potent inhibitors of ACCs from sensitive plants and are in wide use as herbicides (7)(8)(9)(10)(11)(12). These compounds inhibit the CT activity, as does a potent inhibitor of mammalian ACCs, CP-640186 (13), suggesting that the CT domain may be a suitable target for discovering small-molecule inhibitors against ACCs.…”

Cyclohexane-1,3-dione Oxime Ether Grass-Specific Herbicides and the Discovery of Butroxydim

“…8). [18] To illustrate the typical use rates for butroxydim 12 and other cyclohexanedione herbicides, Table 2 shows a comparison of the application rates recommended in 2009 by the Queensland Department of Primary Industry for the control of grass weeds in chickpeas. [19] Similar use rates are also suitable for weed control in many other broad-leaf crops and they demonstrate that butroxydim 12 is the most active of all the cyclohexanediones and similar in activity to the best aryloxyphenoxy herbicide quizalofop.…”