Identification of Herbicide-Resistant Barnyardgrass (Echinochloa crus-galli var. crus-galli) Biotypes in Korea

Abstract

The continuous use of acetolactate synthase (ALS) and acetyl-CoA carboxylase (ACCase) inhibitors has led tothe selection of herbicide resistant barnyardgrass populations in direct-seeded rice fields of Korea. This study was conducted toidentify herbicide resistant barnyardgrass biotypes and to determine the cross- and multiple-resistance of them. 25% of thepopulation collected from Taeahn was partially resistant to ACCase inhibitors and 22% collected from Kimjae were partiallyresistant to ALS inhibitors. However, 8.2% of the population from both sites was resistant to ALS and ACCase inhibitors. Resistance to sulfonylurea herbicide, flazasulfuron was identified from two barnyardgrass accessions collected from both Taeahnand Kimjae. One barnyardgrass accession from both sites was resistant to ACCase inhibitor, sethoxydim. The cross-resistance toALS inhibitors was identified at one barnyardgrass accession from Taeahn and at two accessions from Kimjae. Further, crossresistanceto ACCase inhibitors was also identified at barnyardgrass accessions from Taeahn and Kimjae. Multiple-resistance toflazasulfuron and sethoxydim was determined at four barnyardgrass accessions from Taeahn and at six accessions from Kimjae. Therefore, the herbicide mixture and sequences within a growing season or the herbicide rotation with different modes of actionsacross growing seasons are recommended to control herbicide-resistant barnyardgrass in infested fields.