Skip to main content
ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #298830
Title: Acetolactate synthase-inhibiting herbicide-resistant rice flatsedge (Cyperus iria): Cross resistance and molecular mechanism of resistance

Author
item RIAR, DILPREET - University Of Arkansas
item TEHRANCHIAN, PARSA - University Of Arkansas
item NORSWORTHY, JASON - University Of Arkansas
item Nandula, Vijay
item MCELROY, SCOTT - Auburn University
item SRIVASTAVA, VIBHA - University Of Arkansas
item CHEN, SHU - Auburn University
item BOND, JASON - Delta Research & Extension Center
item SCOTT, ROBERT - University Of Arkansas

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2015
Publication Date: 4/20/2015
Citation: Riar, D.S., Tehranchian, P., Norsworthy, J.K., Nandula, V.K., Mcelroy, S., Srivastava, V., Chen, S., Bond, J.A., Scott, R.C. 2105. Acetolactate synthase-inhibiting herbicide-resistant rice flatsedge (Cyperus iria): Cross resistance and molecular mechanism of resistance. Weed Science. 63:748-757.

Interpretive Summary: Overuse of acetolactate synthase (ALS) –inhibiting herbicides in rice has led to evolution of halosulfuron-resistant rice flatsedge in Arkansas (AR) and Mississippi (MS), USA. Scientists from the University of Arkansas, Crop Production Systems Research Unit (USDA-ARS), Auburn University, and Mississippi State University conducted laboratory and greenhouse studies to understand extent and why rice flatsedge populations are resistant to one or more ALS-inhibiting herbicides. Resistant accessions were cross-resistant to labeled field rates of ALS-inhibiting herbicides from four different families, in comparison to a susceptible (SUS) biotype. Resistance index of AR and MS accessions based on R/S ratio of the lethal dose required for 50% plant mortality (LD50) to bispyribac-sodium, halosulfuron, imazamox, and penoxsulam was >21-fold. Control of AR, MS, and SUS accessions with labeled field rates of 2,4-D, bentazon, and propanil was >93%. An enzyme assay revealed that R/S ratio for 50% inhibition of ALS (I50) for halosulfuron was 2,600 and 200 in AR and MS, respectively. Malathion studies did not reveal enhanced herbicide metabolism in resistant plants. Cross resistance to ALS-inhibiting herbicides along with ALS enzyme assay results with halosulfuron suggest altered target-site resistance and possible multiple mechanisms of resistance. Trp574-Leu amino acid substitution within the ALS gene was found in both AR and MS rice flatsedge accessions using the IlluminaHiseq platform, which corresponds to the mechanism of resistance found in many weed species. Field rate applications of 2,4-D, bentazon, and propanil can be used to control these ALS-resistant rice flatsedge accessions. The above findings will provide valuable knowledge towards devising alternative rice flatsedge control strategies for rice growers of the Midsouth.

Technical Abstract: Overuse of acetolactate synthase (ALS) –inhibiting herbicides in rice has led to evolution of halosulfuron-resistant rice flatsedge (Cyperus iria L.) in Arkansas (AR) and Mississippi (MS), USA. Resistant accessions were cross-resistant to labeled field rates of ALS-inhibiting herbicides from four different families, in comparison to a susceptible (SUS) biotype. Resistance index of AR and MS accessions based on R/S ratio of the lethal dose required for 50% plant mortality (LD50) to bispyribac-sodium, halosulfuron, imazamox, and penoxsulam was >21-fold. Control of AR, MS, and SUS accessions with labeled field rates of 2,4-D, bentazon, and propanil was >93%. An enzyme assay revealed that R/S ratio for 50% inhibition of ALS (I50) for halosulfuron was 2,600 and 200 in AR and MS, respectively. Malathion studies did not reveal enhanced herbicide metabolism in resistant plants. Cross resistance to ALS-inhibiting herbicides along with ALS enzyme assay results with halosulfuron suggest altered target-site resistance and possible multiple mechanisms of resistance. Trp574-Leu amino acid substitution within the ALS gene was found in both AR and MS rice flatsedge accessions using the IlluminaHiseq platform, which corresponds to the mechanism of resistance found in many weed species. Field rate applications of 2,4-D, bentazon, and propanil can be used to control these ALS-resistant rice flatsedge accessions.