Detection of Resistance in Echinochloa spp. to Three Post-Emergence Herbicides (Penoxsulam, Metamifop, and Quinclorac) Used in China

Abstract

In this study, rapid resistance in-season quick (RISQ) tests were developed for detecting the resistance in Echinochloa spp. to penoxsulam, metamifop, and quinclorac, which are widely used in rice fields to control E. spp. biotypes. Seedlings in 1–2 leaf stages from nine biotypes of E. crusgalli, E. crusgalli var. zelayensis, and E. glabrescens, with different susceptibility to the three herbicides tested, were transplanted to plates containing nutrient agar and different rates of herbicides. The survival rates were recorded at 8 days after treatment when no more new roots emerged for all the treatments. By comparing the results from RISQ tests and whole-plant pot bioassays statistically, discrimination rates could be determined to distinguish resistant plants from susceptible plants. For penoxsulam, metamifop, and quinclorac, the discrimination rates were 0.3, 0.6, and 2.4 µmol/L, respectively. Two additional biotypes of E. crusgalli collected in rice fields were used to confirm the validation of the RISQ test and the obtained results by the RISQ test were consistent with that of the whole-plant pot bioassay. Therefore, the developed RISQ test would be a possible alternative method to determine the susceptibility of E. spp. to certain herbicides.