Sourgrass Resistance Mechanism to the Herbicide Glyphosate

ABSTRACT: The knowledge on the mechanism that gives a weed resistance to a particular herbicide is essential regarding scientific, academic, and practical aspects because it determines the recommendations for prevention and management of resistance in the field. Studies on the sourgrass (Digitaria insularis) glyphosate resistance mechanism in the literature have not been conclusive. Thus, the aim of this research was to study and evaluate the putative resistance mechanisms whichgives sourgrass biotypes, the ability to survive after glyphosate application. For this, 14C-glyphosate leaf absorption and translocation were compared in the biotypes Matão (R), Campo Florido (MG), Diamantino (MT), and Iracemápolis (S) as a function of the time after its application. In addition, the possibility that the mechanism of resistance results from a mutation in the EPSPs-encoding gene was also studied. The biotypes S, R, MG, and MT absorbed similar amounts of 14C-glyphosate. The biotypes R, MG, and MT did not present differences in 14C-glyphosate translocation when compared to the biotype S. The sequencing of the EPSPs-encoding gene showed no mutation in the regions 106 and 182, which normally give resistance to glyphosate in the case of other species. No mutation in the EPSPs-encoding gene was observed. Therefore, they are not glyphosate resistance mechanisms for the evaluated biotypes.