MECHANISMS OF RESISTANCE TO ARYLOXYPHENOXYPROPIONATE HERBICIDES IN 2 RESISTANT BIOTYPES OF ALOPECURUS-MYOSUROIDES (BLACKGRASS) - HERBICIDE METABOLISM AS A CROSS-RESISTANCE MECHANISM

The mechanisms of AOPP herbicide resistance in two Alopecurus myosuroi des biotypes were investigated. Resistant biotype Peldon Al, which is highly resistant to the phenyl-urea chlorotoluron, is moderately resis tant to the AOPP herbicides diclofop-methyl, fenoxaprop-ethyl, fluazif op-P-butyl, and the CHD tralkoxydim. Resistant biotype Lines. El, whic h is only moderately resistant to chlorotoluron, is highly resistant t o the AOPP herbicide fenoxaprop-ethyl, and moderately resistant to die lofop-methyl, fluazifop-P-butyl, and the CHD tralkoxydim. There is no clear evidence of resistance to the CHD sethoxydim in either biotype. Both Peldon Al and Lines. El exhibited moderately enhanced metabolism of diclofop-methyl. The approximate half life of diclofop was 8 and 9 HAT,respectively, compared to 17 HAT for the susceptible Rothamsted bi otype. Peldon Al showed moderately enhanced metabolism of fenoxaprop-P -ethyl. However, in the highly resistant Lines. El, fenoxaprop-P-ethyl metabolism rates were intermediate between Perdon Al and the suscepti ble biotype. Fenoxaprop-P-ethyl metabolism in A. myosuroides was not s ignificantly reduced by inhibitors of cytochrome P450: PBO, tetcyclasi s, or ABT. While enhanced herbicide metabolism can account for the mod erate AOPP/CHD resistance observed in Peldon Al in vivo, it cannot acc ount in total for fenoxapropethyl resistance in Lines. El. Lines. El m ay possess one or more additional resistance mechanism. (C) 1997 Acade mic Press.