First report of barnyardgrass resistant to glyphosate in Brazil

• Published in: Advances in Weed Science Vol. 43; p. e020250081
• Main Authors: Oliveira, Claudia de, Mathioni, Sandra M., Riaño, Alejandra D., Camargo, Edinalvo R., Dornelles, Sylvio H.B., Lemes, Lúcio N., Ozório, Eduardo G., Avila, Luis A.
• Format: Journal Article
• Language: English
• Published: Londrina Sociedade Brasileira da Ciência das Plantas Daninhas, UFV - Depto de Fitotecnia 01.01.2025; Sociedade Brasileira da Ciência das Plantas Daninhas - SBCPD
• Subjects: AGRONOMY; Alanine; Crops; Dry weight; Echinochloa crus-galli; EPSPS gene; Fertilization; Glyphosate; Herbicide resistance; Herbicides; Loam soils; Mutation; Plant extracts; Populations; Regression models; Resistance factors; Seeds; Self-fertilization; Soybeans; Weight reduction; Brazil; EPSPs-Inhibiting Resistance; Echinochloa Crus-galli; Mutation
• ISSN: 2675-9462; 2675-9462
• DOI: 10.51694/AdvWeedSci/2025;43:00010

Background Barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.) is an annual weed affecting many field crops. A glyphosate-putative-resistant barnyardgrass population was found from a soybean field in southern Brazil.Objective This study aimed to confirm this resistance in Rio Grande do Sul (RS) and identify its mechanism.Methods Dose-response curves were generated using a three-parameter nonlinear regression model to assess control efficacy and shoot dry weight reduction. Resistance factors (RF) were calculated across two generations from the resistant (BR20Esp016) and susceptible (BR19Esp001) populations. cDNA was synthesized from total RNA extracted from the plants, and the EPSPS gene was sequenced from both populations.Results Based on the glyphosate required to reduce dry weight by 50% (GR50), the resistance biotype had RFs of 2.4 and 2.6 and values of 2.4 and 13.9 for the same variable for the self-fertilization generation (F2). A mutation was detected in the EPSPS gene, where proline (CCA) is replaced by alanine (GCA) at position 106, conferring resistance to EPSPS-inhibiting herbicides in barnyardgrass.Conclusion Glyphosate resistance in the barnyardgrass biotype BR20Esp016 is due to target-site resistance associated with a mutation in the EPSPS gene.