Estudo da resistência ao glyphosate em biótipos de leiteiro (Euphorbia heterophylla L.) sobreviventes ao herbicida no estado do Paraná

Abstract

One of the main challenges in modern agriculture is the emergence of herbicide- resistant weed species. Euphorbia heterophylla (wild poinsettia) is one of the most problematic weeds in Brazil due to its biological characteristics, which enhance its competitiveness with crops, and because biotypes of this species have developed resistance to multiple herbicide modes of action. This study aimed to investigate the resistance of the F1 generation of seven E. heterophylla biotypes collected from different municipalities in Paraná, Brazil, through dose–response curves to glyphosate, and to infer whether glyphosate resistance is inheritable to subsequent generations. The experiment was conducted in a greenhouse using a completely randomized design in a factorial scheme (seven biotypes × six glyphosate doses: 0, 260, 520, 1040, 2080, 4160, and 8320 g a.e. ha⁻¹). Visual control at 7, 14, and 21 days after application (DAA), plant height at 14 and 28 DAA, and fresh biomass at 28 DAA were evaluated. Results showed variability in the response of biotypes to glyphosate doses. Biotype 4, exhibited the highest level of resistance, showing lower control rates and higher biomass even at elevated doses. It was concluded that all biotypes showed some level of resistance, and this trait is inheritable, as observed in the survival of the firts generation under recommended doses. The study highlights the need for integrated weed management and continuous monitoring to mitigate the evolution of resistance.