EK‐2612, a new cyclohexane‐1,3‐dione possessing selectivity between rice ( Oryza sativa ) and barnyardgrass ( Echinochloa crus‐galli )

A newly synthesized experimental compound, EK-2612 is one of the class of cyclohexane-1,3-diones which are commonly known to be grasskillers. A greenhouse study was conducted to evaluate the herbicidal performances of EK-2612 on several grass species in comparison with tralkoxydim, a commercialized cyclohexanedione derivative. Like tralkoxydim, the compound EK-2612 showed excellent control efficacy on most grass weeds tested through foliar application rates between 250 and 63 g AI ha(-1). Unlike tralkoxydim, however, EK-2612 showed a good rice safety, and there was no rice damage observed at the level below 125 g AI ha(-1), while rice injury developed at the same application rates of tralkoxydim. With this rice safety, EK-2612 controlled barnyardgrass effectively up to the two-leaf stage under both submerged and dried paddy conditions. An in vitro ACCase assay indicated that EK-2612 is a strong ACCase inhibitor; however, the dose-response was not substantially different in rice and barnryardgrass, showing I50 values of 0.1 and 0.12 microM, respectively. These results suggest that the compound EK-2612 is targeting plant ACCase, but the whole-plant rice safety is not attributable to a different inhibition of the target site in rice from that in barnyardgrass.