Glyphosate-resistant weeds of South America: An overview

VILA-AIUB MM

Chicago, Illinois, (USA)

Conferencia; American Chemical Society; 2007

Herbicide resistance in weeds is an evolutionary event whichresults of two combining factors: intense selection pressureand genetically-diverse weed populations. In South America,orchard (Argentina, Brazil, Chile) and cereal-legume(Argentina, Brazil) production systems show a strongreliance on glyphosate use as a pre-plant and preemergenceherbicide to control weed populations. This trendhas been magnified in the last years given the massiveadoption of no-till glyphosate-resistant (GR) soybean cropsin Argentina mainly and in Brazil. These crops allow the useof glyphosate as an in-crop herbicide. This agriculturaltechnology facilitates the conditions to make these croppingsystems ecologically vulnerable for evolution of GR weeds.The first glyphosate-resistance cases include highly- andgenetically-diverse, annual weeds (Lolium multiflorum,Coniza bonariensis, C. canadensis) after recurrent strongglyphosate selections in Chilean and Brazilian fruitproductions. Recently, the appearance of GR Sorghumhalepense and Euphorbia heterophylla populations inArgentinean and Brazilian GR soybean fields, respectively,are of major concern. The present review summarizes thecurrent knowledge on the physiology, ecology, andagronomy of all the mentioned GR weeds.