GOOSEGRASS RESISTANT TO GLYPHOSATE IN BRAZIL

Several cases of herbicide resistance in goosegrass have been confirmed worldwide. Reports of control failures after glyphosate application have been observed, especially in the Midwest region of Parana State. The objective of this study was to evaluate the existence of goosegrass populations resistant to glyphosate. For this, 25 populations collected in two consecutive seasons (2013/2014 and 2014/2015) were sown and grown in greenhouse. Glyphosate dose-response curve experiments were performed using doses of 0, 60, 120, 240, 480, 960, 1,920, 3,840, 7,680 and 15,360 g a.e. ha(-1). The application stages were from two to three tillers (E1) for the populations of 2013/2014 and E1 and five to six tillers (E2) for the populations of 2014/2015. Furthermore, three of the populations supposedly considered resistant in these experiments (populations 7, 19 and 25) have had their F1 submitted to the herbicide dose-response test in order to verify whether the resistance was inheritable. With the results obtained in this study, it was concluded that the populations 19 and 25, from Campo Mourao and Luziania (Midwest of Parana) are the first confirmed cases of goosegrass resistant to glyphosate in Brazil (RF = 3.99 to 6.81), following all the criteria for confirmation of new weed resistance cases.