|DE Prado, R - UNIV. OF CORDOBA, SPAIN|
|Plaisance, K - UNIVERSITY OF MINNESOTA|
|Menendez, J - 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: A biotype of Alopecurus myosuroides resistant to high rates of chlorotoluron was found in northeastern Spain. This biotype exhibited cross-resistance to several graminicides. Herbicide concentrations required to inhibit shoot growth by 50% (ED 50 values) were determined for both resistant and susceptible biotypes for five aryloxyphenoxypropionates (clofinafop-propargyl, diclofop-methyl, fluazifop-p-butyl, haloxyfop- methyl, propaquizafop) and three cyclohexanediones (cycloxydim, sethoxydim, tralkoxydim). Compared to the susceptible biotype, the resistant biotype was 6.9, 11.0, 2.1, 2.1, 11.6, 2.1, 2.2, and 7.5-fold more resistant to the eight herbicides, respectively. Concentrations of diclofop, fluazifop, and haloxyfop that inhibited acetyl-CoA carboxylase (ACCase) by 50% (I 50 values) were 2.6, 3.8, and 5.1-fold greater, respectively, for the ACCase isolated from the resistant biotype compared to the susceptible biotype. For the cyclohexanediones clethodim, cycloxydim and tralkoxydim, the I 50 values were 1.5, 1.6, and 2.1-fold greater, respectively, for ACCase isolated from the resistant biotype. These results suggest that tolerance to the aryloxyphenoxypropionate and cyclohexanedione herbicides in the chlorotoluron-resistant biotype of Alopecurus myosuroides is not due to the presence of a tolerant form of ACCase.