Seed-bioassay to detect grass weeds resistant to acetyl coenzyme A carboxylase inhibiting herbicides

A seed-bioassay was developed to identify grass weed populations resistant to acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides. Lolium rigidum, Phalaris minor and Alopecurus myosuroides resistant to diclofop, fenoxaprop-P and clodinafop, respectively, were tested using seed-bioassay and the results were compared with those obtained from the whole-plant trial and enzyme assay. A close association was found between the results from seed-bioassay and the other methods suggesting that it is a reliable, rapid, simple and cheap method for identifying populations of grass species resistant to ACCase-inhibiting herbicides. Furthermore, the method could detect effectively cross-resistance of grass weeds to other ACCase-inhibiting herbicides. According to the seed-bioassay the discriminating concentrations for R and S biotypes of L. rigidum, P. minor and A. myosuroides were at 6.0, 8.0 and 0.06 mg/l, for diclofop, fenoxaprop-P and clodinafop, respectively. (C) 2000 Elsevier Science Ltd.