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1 September 2017 Cross-Resistance of Eclipta (Eclipta prostrata) in China to ALS Inhibitors Due to a Pro-197-Ser Point Mutation
Dan Li, Xiangju Li, Huilin Yu, Jingjing Wang, Hailan Cui
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Eclipta, widespread in tropical, subtropical, and temperate regions, is one of the main malignant broadleaf weeds and thrives in moist and dryland fields. Field rates of acetolactate synthase (ALS) inhibitors have failed to control eclipta in some farmlands in China. One ALS inhibitor–resistant population (R) collected from Jiangsu province in China was confirmed in the greenhouse in our preliminary work. Whole-plant assays revealed that this R population was highly resistant to four sulfonylureas (pyrazosulfuron-ethyl, 134-fold; bensulfuron-methyl, 172-fold; metsulfuron-methyl, 30-fold; and tribenuron-methyl, 195-fold), two triazolopyrimidines (pyroxsulam, 98-fold; penoxsulam, 30-fold), and one pyrimidinylthio-benzoate (bispyribac-sodium, 166-fold) and was moderately resistant to two imidazolinones (imazethapyr, 10-fold; imazapic, 19-fold). ALS enzyme-activity assays showed insensitivity of the ALS from the R population (resistance index values ranged from 12 to 293) to all of the above ALS inhibitors in vitro. Chromatograms from ALS gene sequence analysis detected a homozygous Pro-197-Ser amino acid substitution in the R population. These results confirmed that the Pro-197-Ser substitution results in broad-spectrum cross-resistance to ALS inhibitors in the eclipta R population. To our knowledge, this study is the first to report broad cross-resistance to ALS inhibitors in eclipta and to obtain the full-length ALS gene sequence.

Nomenclature: bensulfuron-methyl; bispyribac-sodium; imazapic; imazethapyr; metsulfuron-methyl; penoxsulam; pyrazosulfuron-ethyl; pyroxsulam; tribenuron-methyl; eclipta, Eclipta prostrata (L.) L.

© Weed Science Society of America, 2017
Dan Li, Xiangju Li, Huilin Yu, Jingjing Wang, and Hailan Cui "Cross-Resistance of Eclipta (Eclipta prostrata) in China to ALS Inhibitors Due to a Pro-197-Ser Point Mutation," Weed Science 65(5), 547-556, (1 September 2017).
Received: 15 December 2016; Accepted: 1 March 2017; Published: 1 September 2017
ALS inhibitor resistance
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