First case of glyphosate resistance in weedy sunflower (Helianthus annuus). Issue 11 (15th July 2020)

• Record Type: Journal Article
• Authors: Singh, Vijay; Etheredge, Luke; McGinty, Josh; Morgan, Gaylon; Bagavathiannan, Muthukumar
• Is Part Of: Pest management science. Volume 76:Issue 11(2020)
• Page Start: 3685
• Page End: 3692
• Publication Date: 2020-07-15
• Subjects: common sunflower -- herbicide screening -- gene copy number -- selection pressure -- weed resistance; Pests -- Control -- Periodicals; Pesticides -- Periodicals; 632.9
• DOI: 10.1002/ps.5917
• Languages: English
• ISSNs: 1526-498X

Abstract

Abstract: BACKGROUND: Weedy sunflower ( Helianthus annuus L.) is a troublesome weed in row‐crop production fields in South Texas. Populations with suspected resistance to glyphosate were evaluated with 1X and 4X rates (X = 868 g ae ha −1 ) of the herbicide, followed by a dose–response assay of the most resistant population. Molecular studies were conducted to determine if target‐site mechanisms were responsible for resistance in these populations. Additionally, field experiments were conducted at two locations (Somerville and Granger, TX) to evaluate the effectiveness of different tank‐mix combinations in controlling naturally infesting glyphosate‐resistant (GR) weedy sunflower populations in GR corn. RESULTS: In a study conducted in the growth chamber, seven of the 11 tested populations survived up to the 4X rate of glyphosate. The most‐resistant population (TX15‐11) was 29‐fold more resistant to glyphosate, compared to the susceptible standard. In resistant populations, 5–21 more copies of the EPSPS gene were observed compared to the susceptible standard. In the field studies, tank‐mix applications of glyphosate + halosulfuron‐methyl, glyphosate + prosulfuron, glyphosate + a premix of halosulfuron‐methyl and dicamba or glyphosate + a premix of diflufenzopyr and dicamba effectively controlled GR weedy sunflower populations. CONCLUSION: Glyphosate‐resistance was observed in 81% of the putative resistant weedy sunflower populations tested in this study. Resistance in these populations was conferred primarily by amplification of the EPSPS gene. Effective control of GR weedy sunflower can be achieved by tank‐mixes tested in the current study, which provides acceptable levels of crop safety. © 2020 Society of Chemical Industry Abstract : Weedy sunflower is a growing issue in South Texas. In this research, we confirmed the first case of glyphosate‐resistant weedy sunflower and identified alternative control options. © 2020 Society of Chemical Industry