Target-site basis for resistance to flucarbazone- sodium in Japanese brome (Bromus japonicus Houtt.) in China

Abstract

Japanese brome (Bromus japonicus Houtt.) is a troublesome annual weed and widely distributed in winter wheat (Triticum aestivum L.) fields in the North China Plain. A B. japonicus population (TJ06) suspected of resistance to acetolactate synthase (ALS) inhibitors was found in Tianjin, China. In this study, the TJ06 population with an Asp-376-Glu mutation in ALS gene was identified. TJ06 population developed 66.7-fold resistance to flucarbazone-sodium and exhibited obvious cross-resistance to other two ALS-inhibiting herbicides. The 50% plant growth reduction (GR50) to herbicides of pyroxsulam and mesosulfuron-methyl were 28.72 and 39.44 g ai ha -1 , respectively. In in vitro ALS activity assays, the concentration of flucarbazone-sodium required to inhibit 50% ALS activity (I50) for TJ06 was 11.3-fold greater than that for a susceptible population (TJ01), which was highly correlated with that of whole-plant response experiments and indicated that the Asp-376-Glu mutation leading to resistance reduced sensitivity of the ALS enzyme to flucarbazonesodium. Besides, one derived cleaved amplified polymorphic sequence (dCAPS) marker was designed to quickly detect Asp376 mutation in ALS gene of B. japonicus.