Peroxidase activity in glyphosate-resistant and susceptible biotypes of Lolium perenne

YANNICCARI, MARCOS; ACCIARESI HORACIO; ISTILART CAROLINA; GIMÉNEZ DANIEL; CASTRO ANA MARÍA

Baltimore

Congreso; 2013 WSSA Annual Meeting - Northeastern Weed Science Society Conference.; 2013

WSSA

Ryegrass (Lolium sp.) is a common weed in wheat and barley crops in the South region of Buenos Aires province (Argentina). Glyphosate is frequently used to control weeds on field prior to crop sowing or emergence. In the last years, several Lolium spp. populations were characterized as glyphosate-resistant weeds. The aim of this work was to assess the glyphosate effects on peroxidase activity of glyphosate-resistant and susceptible Lolium perenneL. biotypes. Perennial ryegrass plants were grown in a greenhouse and treated with 1,020 g ae ha-1 of glyphosate. The last expanded leaves were sampled at 0, 24, 48 and 72 hours post-application (HPA). Peroxidase activity was measured by spectrophotometer at 430nm in a reaction medium consisting of 50 mM potassium phosphate buffer (pH 6.5), 45 mM pyrogallol and 8 mM H2O2. The activity was estimated from the reduction of pyrogallol to purpurogallin. At 72 HPA, peroxidase activity increased one fold in susceptible treated plants compared to their controls, while glyphosate-resistant plants showed no significant changes in the enzyme activity during all experiment. These results are consistent with previous reports which involved the generation of reactive oxygen species after glyphosate application that provoke oxidative damage. However, it was a relatively later event compared to the glyphosate effects on leaf gas exchange reported previously. The current study thus provides evidences in the phytotoxic effects that are triggered in response to glyphosate application. In addition, it specifies the mechanisms by which the herbicide affects susceptible plants and it characterizes the glyphosate-resistant L. perenne plants physiologically.