Goosegrass (Eleusine indica) Resistant to Multiple Herbicide Modes of Action in Brazil

Abstract This study was developed based on a goosegrass [Eleusine indica (L.) Gaertn.] population from Primavera do Leste, MT, Brazil, with resistance to multiple herbicide modes of action (5-enol-pyruvylshikimate-3-phosphate synthase [EPSPS] inhibition: glyphosate; acetyl-coenzyme A carboxylase [ACCase] inhibition: aryloxyphenoxypropionate chemical group). The objective was to identify possible mechanisms of resistance associated or not with herbicide sites of action. Several experiments and analyses were carried out with the contribution of different laboratories and institutions. The results obtained allowed us to conclude that: (1) the Asp-2078-Gly mutation conferred resistance to ACCase inhibitors, without overexpression of ACCase or changes in herbicide absorption and translocation; (2) overexpression of EPSPS, Thr-102 and Pro-106 mutations, and changes in absorption and translocation are not involved in E. indica resistance to glyphosate; (3) the metabolism of glyphosate in resistant E. indica plants requires further studies to elucidate the final destination of this herbicide in these plants. The mechanism of resistance of E. indica biotypes to ACCase-inhibiting herbicides was elucidated: it involves a change in the action site. However, the mechanism of resistance to EPSPS inhibitors was not conclusive, indicating that some hypotheses, mainly those regarding the metabolism of glyphosate in resistant plants, require further testing.