Elucidating the Mechanisms of Herbicide Resistance in Barnyardgrass (Echinochloa crus-galli L.) Populations from Brazil.

• Grant number: 15/19163-2
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: December 01, 2015
• End date: June 30, 2016
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Valdemar Luiz Tornisielo
• Grantee: Bianca Assis Barbosa Martins
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

In Brazil, a significant increase in the frequency and diversity of herbicide-resistant weeds has been observed over the last 15 years, which represents a threat to the sustainability of Brazilian agriculture. Long-term research and extension efforts towards the knowledge about the mechanisms of herbicide resistance contributes to the improvement of crop protection measures and, consequently, to profitable farming of Brazilian growers.Using Echinochloa crus-galli populations that are susceptible or resistant to the auxinic herbicide quinclorac, the objective of this project is to evaluate putative mechanisms of resistance at the molecular and physiological levels. Echinochloa crus-galli is an excellent model species for uncovering the mode of action of auxinic herbicides, as well as resistance to these compounds. Such studies are still incipient in Brazil. To accomplish the project, alignment and comparison of the auxin receptor genes between the resistant and the susceptible E. crus-galli populations will be conducted. For studying absorption, translocation and metabolism of quinclorac in planta, radiolabeled [14C]quinclorac will be used and radioactivity will be traced by liquid scintillation spectrometry, phosphor imaging, and high-performance liquid chromatography. Identification of potential metabolites will be achieved by high resolution mass spectrometry. The expected outcome is that there will be an alteration at the molecular and / or physiological levels in the resistant E. crus-galli population compared to the susceptible one. The results of this study will provide better understanding of the mechanisms involved in resistance to auxinic herbicides, as well as the initial auxin-signaling pathway in the plant. This study will allow comparisons with cases of herbicide resistance that occur in other parts of the world, stimulating shifts in weed control tactics towards more sustainable cropping systems in Brazil.