Characterization of the resistance mechanism of smallflower galinsoga (Galinsoga parviflora) to linuron and glyphosate in agricultural areas in Brazil

• Grant number: 24/10294-6
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: February 01, 2026
• End date: January 31, 2029
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Kassio Ferreira Mendes
• Grantee: Saeid Hassanpourbourkheili
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Herbicide resistance is major threat to sustainable agriculture, and Brazil is among the countries with the highest number of resistant cases in the world. Recently, there are reports concerning development of resistance to glyphosate and linuron in smallflower galinsoga (Galinsoga parviflora Cav.) in Brazil. Therefore, the present study will investigate mechanisms of resistance to these herbicides in smallflower galinsoga. First putative biotypes will be screened using the recommended rate of glyphosate and linuron to confirm their resistance. The resistant biotypes will then undergo dose-response assays, and the resistance index (RI) will be estimated. Also, response of glyphosate- and linuron- resistant and susceptible biotypes to herbicides from various chemical groups and mode of action, including as ioxynil, quizalofop, clethodim, flumioxazin, trifluralin, diuron, 2-4-D, dicamba, rimsulfuron, ammonium-glufosinate and pendimethalin will be evaluated. Target site resistance (TSR) assays will be performed on EPSPS and bspA genes. Non-target site resistance (NTSR) assays including absorption, translocation, and metabolism with 14C-herbicides will also be done. The results of this study can help to devise weed management approaches and rapid resistance detection and screening methods. If confirmed, this will be the first report on the mechanism of resistance to glyphosate and linuron in smallflower galinsoga in Brazil as well as in the world. (AU)