|Gasquez, J - INRA, FRANCE|
|Gimenez-Espinosa, R - UNIV. OF CORDOBA, SPAIN|
|DE Prado, R - UNIV. OF CORDOBA, SPAIN|
Submitted to: International Symposium on Weed & Crop Resistance to Herbicides Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 5, 1996
Publication Date: N/A
Technical Abstract: Poor control of a Lolium multiflorum biotype by graminicides has been observed for the past 4 to 5 years in a field in Normandy. Experiments conducted in the greenhouse with plants in the 3-4 leaf stage indicated that the resistant biotype exhibited 100% and 34% survival when treated with 5760 g/ha and 23040 g/ha diclofop, respectively. This biotype is also oresistant to fluazifop, clodinafop, and low levels of cycloxydim, but is not resistant to quizalofop, alloxydim or sethoxydim. The resistant biotype exhibited no cross-resistance to recommended field rates of atrazine, diuron, chlorotoluron, propyzamide, alachlor, metolachlor or benfluralin. The susceptibility of acetyl-CoA carboxylase (ACCase) activity to aryloxyphenoxypropionate and cyclohexanedione herbicides was measured in leaf extracts from resistant and susceptible biotypes. The I50 values (herbicide concentrations that inhibit enzyme activity by 50%) for diclofop, fluazifop, and haloxyfop were approximately 39, 89, and 19-fold greater, respectively, for the resistant biotype compared to the susceptible biotype. For the cyclohexanediones, clethodim, cycloxydim, and sethoxydim, the I50 values were approximately 3, 5, and 5-fold greater for the resistant biotype. The results suggest that resistance to the aryloxyphenoxypropionates in the Lolium biotype is due to the presence of a mutant, herbicide-resistant form of ACCase.