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

Qi Li1, Jinping Yu1, Wenlei Guo2, Long Du3, Penghua Bai1, and Yixue Liu1*
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 flucarbazone- sodium. Besides, one derived cleaved amplified polymorphic sequence (dCAPS) marker was designed to quickly detect Asp376 mutation in ALS gene of B. japonicus.
Keywords: ALS, Bromus japonicus, dCAPS, gene mutation, herbicide resistance.
1Institute of Plant Protection, Tianjin Academy of Agricultural Sciences, Tianjin 300381, PR China. *Corresponding author (liuyixue430@163.com). 2Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences/Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Guangzhou 510640, PR China.3Pest Bio-control Lab, Shandong Peanut Research Institute, Qingdao 266041, PR China.