First report of resistence to acetolactate synthase inhibiting herbicides in yellow nutsedge (Cyperus esculentus): confirmation and characterization

Authors: TEHRANCHIAN, PARSA - University Of Arkansas; NORSWORTHY, JASON - University Of Arkansas; Nandula, Vijay; MCELROY, SCOTT - Auburn University; CHEN, SHU - Auburn University; SCOTT, ROBERT - University Of Arkansas

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2014
Publication Date: 11/10/2014
Citation: Tehranchian, P., Norsworthy, J.K., Nandula, V.K., Mcelroy, S., Chen, S., Scott, R.C. 2014. First report of resistence to acetolactate synthase inhibiting herbicides in yellow nutsedge (Cyperus esculentus): confirmation and characterization. Pest Management Science. 71(9):1274-1280.

Interpretive Summary: Yellow nutsedge is one of the most problematic weeds in rice producing acres of the Midsouth. The herbicide halosulfuron (sulfonylurea) is frequently used for its control. In the summer of 2012, halosulfuron at recommended field rates failed to control yellow nutsedge in certain rice fields of Arkansas, thereby, making management matters worse. Scientists from the University of Arkansas, Crop Production Systems Research Unit (USDA-ARS), and Auburn University conducted laboratory and greenhouse studies to understand extent and why yellow nutsedge populations are resistant to one or more ALS-inhibiting herbicides. The level of resistance to halosulfuron was very high with none of the resistant plants killed by halosulfuron at a dose of 13,568 g ha-1 (256X the field dose). Based on the whole plant bioassay, the resistant biotype was not controlled by any of the ALS-inhibiting herbicides (imazamox, imazethapyr, penoxsulam, bispyribac, pyrithiobac-sodium, bensulfuron, and halosulfuron) tested at the labeled field rate. The ALS enzyme from the resistant biotype was 2,540 times less responsive to halosulfuron than the susceptible biotype, and a Trp574 to Leu substitution was detected by ALS gene sequencing using the Illumina HiSeq. The above results suggest a target-site alteration as the mechanism of resistance in yellow nutsedge, which accounts for the cross-resistance to other ALS inhibiting herbicide families. The above findings will provide valuable knowledge towards devising alternative yellow nutsedge control strategies and minimizing impact on rice growers of the Midsouth.

Technical Abstract: Yellow nutsedge is one of the most problematic sedges in Arkansas rice, requiring the frequent use of halosulfuron (sulfonylurea) for its control. In the summer of 2012, halosulfuron at 53 g ha-1(labeled field rate) failed to control yellow nutsedge. The level of resistance to halosulfuron was determined in the putative resistant biotype and its cross-resistance to other acetolactate synthase (ALS) inhibitors from four different herbicide families. ALS enzyme assays and analysis of the ALS gene were used to ascertain the resistance mechanism. None of the resistant plants were killed by halosulfuron at a dose of 13,568 g ha-1 (256X the field dose), indicating a high level of resistance. Based on the whole plant bioassay, the resistant biotype was not controlled by any of the ALS-inhibiting herbicides (imazamox, imazethapyr, penoxsulam, bispyribac, pyrithiobac-sodium, bensulfuron, and halosulfuron) tested at the labeled field rate. The ALS enzyme from the resistant biotype was 2,540 times less responsive to halosulfuron than the susceptible biotype, and a Trp574 to Leu substitution was detected by ALS gene sequencing using the Illumina HiSeq. The results suggest a target-site alteration as the mechanism of resistance in yellow nutsedge, which accounts for the cross-resistance to other ALSinhibiting herbicide families.