Baseline sensitivity of Echinochloa cruss-galli collected in Korea

Abstract

ABSTRACT

Baseline sensitivity of Echinochloa crus-galli collected in Korea

Aceotolactate (ALS) and acetyl CoA carboxylase (ACCase) inhibitor resistant Echinochloa species now become problematic in Korean rice cultivation. Alternative herbicides with different modes of action can be used to control these herbicide resistant Echinochloa species. However, continuous uses of these alternative herbicides will eventually make the Echinochloa species become resistant to these herbicides as well. Therefore, this study was conducted to evaluate baseline sensitivity of Echinochloa crus-galli to the alternative herbicides selected for managing herbicide resistant Echinochloa species. 63 accessions of Echinochloa crus-galli collected across Korea were tested by whole plant assay. Four VLCFAs inhibitors, mefenacet, pretilachlor, fentrazamide, cafenstrole, one PPO inhibitor, oxadiargyl, and one herbicide with unknown mode of action, oxaziclomefone, were directly applied to the flooded paddy soil at a range of their doses when Echinochloa reached the 2 leaf stage. GR80 values of mefenacet, pretilachlor, fentrazamide, cafenstrole, oxadiargyl, and oxaziclomefone ranged 12.67 - 3544.84 g a.i. ha-1, 12.20 - 372.98 g a.i. ha-1, 2.68 - 58.16 g a.i. ha-1, 34.35 - 95.21 g a.i. ha-1, 4.68 - 461.50 g a.i. ha-1, and 0.34 – 25.81 g a.i. ha-1, respectively. Selectivity indices were 250.68, 30.57, 21.70, 2.77, 111.25, and 81.68 for mefenacet, pretilachlor, fentrazamide, cafenstrole, oxadiargyl, and oxaziclomefone, respectively, suggesting that mefenacet has the greatest potential risk of resistance evolution, followed by oxadiargyl, while cafenstrole has the lowest risk of resistance evolution. However, continuous use of these herbicides may eventually result in herbicide resistance to these herbicides.