Resistance to BAY MKH 6562 in Wild Oat (Avena fatua)1

摘要

Abstract:BAY MKH 6562 [flucarbazone-sodium (proposed)], an acetolactate synthase (ALS)-inhibiting herbicide of the sulfonylaminocarbonyltriazolinone family, provides postemergence wild oat control in wheat. Whole-plant dose responses and in vitro ALS sensitivity assays were used to evaluate the magnitude and nature of cross-resistance to BAY MKH 6562 in a wild oat accession (AR1) with metabolism-based resistance to imazamethabenz, an ALS inhibitor of the imidazolinone family. An imazamethabenz-susceptible wild oat accession (AHS2), five BAY MKH 6562-resistant wild oat accessions, AN104, AN205, AN307, AN406, and ASB11, and wheat were also evaluated. AHS2 and AR1 dose responses to BAY MKH 6562 indicated a resistant/susceptible (R/S) herbicide dose required to cause 50% growth reduction (GR₅₀) ratio of 200. Inhibition of ALS from the AHS2 and AR1 wild oat by BAY MKH 6562 was similar, with a concentration of herbicide required to cause 50% inhibition of enzymatic activity (I₅₀) of 0.007 µmoles, indicating that cross-resistance was not due to an altered ALS enzyme. The GR₅₀ for BAY MKH 6562 for the AN104, AN205, AN307, AN406, and ASB11 wild oat accessions was 0.23, 0.07, 0.23, 0.22, and 0.12 kg ai/ha, respectively, and the R/S ratio to the GR₅₀ value for the AHS2 accession was 230, 70, 230, 220, and 120, respectively. Studies on ALS sensitivity to BAY MKH 6562 indicated that the I₅₀ for the AN104, AN205, AN307, AN406, and ASB11 wild oat accessions was 5.2, 0.003, 0.008, 9.8, and 0.007 µmoles, respectively, and the R/S ratio to the I₅₀ value for the AHS2 accession was 759, 0.5, 1, 1,444, and 1, respectively. Of the five wild oat accessions resistant to BAY MKH 6562, accessions AN104 and AN406 had high R/S I₅₀ ratios indicative of an altered target site and accessions AN205, AN307, and AR1 had low R/S I₅₀ ratios indicative of resistance based on metabolic degradation. Hard red spring wheat (2371) was 800-fold tolerant to BAY MKH 6562 and inhibition of ALS from wheat by BAY MKH 6562 was similar to that of ALS from the susceptible accession AHS2.