Elucidação do mecanismo de resistência de >i<Digitaria nuda>/i< Schumach. aos herbicidas inibidores da Acetil coenzima A carboxilase (ACCase)

Abstract

Elucidation of the resistance mechanism of Digitaria nuda Schumach. to Acetyl-CoA Carboxylase (ACCase)-inhibiting herbicidesResistance of Digitaria nuda to ACCase-inhibiting herbicides was investigated in a population from Rio Verde, Brazil.Dose-response assays confirmed high resistance to haloxyfop, fluazifop, propaquizafop, fenoxaprop, and quizalofop (resistance factors >60x in some cases), while clethodim remained effective at high doses and glyphosate controlled the population, indicating no multiple resistance.Molecular analysis revealed the Ile2041Asn mutation in the ACCase gene of the resistant population, a mutation conferring resistance to FOP herbicides.Digital PCR showed no significant differences in ACCase gene expression between resistant and susceptible biotypes, suggesting overexpression is not involved in the resistance mechanism.Further experiments found no significant differences in absorption, but significant differences in translocation between biotypes, demonstrating that differential translocation is involved in resistance.Cytochrome P450-mediated detoxification of haloxyfop was not involved in the resistance mechanism of D. nuda.This confirms the first case of ACCase inhibitor resistance in D. nuda in Brazil, associated with the Ile2041Asn mutation.The absence of multiple resistance suggests that management strategies such as rotating modes of action and using clethodim or glyphosate can be effective.More than one mechanism is involved in the resistance of D. nuda to ACCase inhibitors.