Molecular Survey of Glyphosate and PPO-Inhibitor Resistance Mechanisms in Ohio Tall Waterhemp Populations

MARK LOUX; BRENT MURPHY; PATRICK TRANEL; ALVARO LARRAN; BRUCE ACKLEY

Saint Louis

Encuentro; 72nd Annual Meeting of the North Central Weed Science Society; 2017

The spread and prevalence of herbicide resistance within driver species such as Amaranthus tuberculatus impact management options available to producers. Here we outline the spatial distribution of known mechanisms of resistance to key herbicides glyphosate, PPO inhibitors, and atrazine within A. tuberculatus in the state of Ohio. In regards to glyphosate resistance, EPSPS gene-amplification was observed in nearly all tested populations, whereas the P106S EPSPS substitution occurred infrequently. Several instances of a glyphosate-resistant plant possessing both gene amplification and the P106S mutation were observed. Resistance to PPO inhibitors mediated by the PPO G210 deletion was observed in high frequency in two populations in Mercer County and Hardin County. No instances of R98 PPO mutations were observed within PPO-inhibitor-resistant plants. Resistance to atrazine was observed at low frequencies in most tested populations, however high frequencies of atrazine resistance were observed in a single population in Mahoning County and Mercer County. No instances of the G264S D1 substitution, which confers atrazine resistance, were observed in the tested populations. Continued surveillance of target weedy species is necessary to maintain accurate information for producers, allowing optimal management decisions to be made.