Glyphosate resistance in Echinochloa colona: phenotypic characterization and quantification of selection intensity

GOH, SS; VILA AIUB, MM; BUSI, R.; POWLES, SB

PEST MANAGEMENT SCIENCE

JOHN WILEY & SONS LTD

Lugar: Londres; Año: 2016

1526-498X

BACKGROUND: A population of Echinochloa colona infesting agricultural fieldsin the northern region of Western Australia evolved glyphosate resistance after 10years of glyphosate selection. This study identified two phenotypic (susceptibility ?S?vs resistance ?R?) lines from within a segregating glyphosate-resistant population.Estimation of survival, growth and reproductive rates of the phenotypes in responseto glyphosate selection helped characterize the level of resistance, fitness and theselection intensity for glyphosate in this species.RESULTS: Estimations of LD50 (lethal dose) and GR50 (growth rate) have shown a8-fold glyphosate resistance in this population. The resistant index based on theestimation of seed number (SYn50) shows a 13-fold resistance. As a result of linearcombination of plant survival and fecundity rates, plant fitness of 0.2 and 0.8 wasestimated for the S and R phenotypes when exposed to the low dose of 270 gglyphosate ha-1. At the recommended dose of 540 g glyphosate ha-1 fitnesssignificantly decreased 5-fold in S plants but remained markedly similar (0.7) inplants of the R phenotype. Thus, the calculated selection intensity (SI) at 540 gglyphosate ha-1 was much greater (SI = 17) than at 270 g glyphosate ha-1 (SI = 4).CONCLUSIONS: The assessment of plant survival and fecundity in response to glyphosateselection in the S and R phenotypes allowed a greater accuracy in the estimation ofpopulation fitness of both phenotypes and thus the glyphosate selection intensity in E. colona.The estimation of seed number or mass of phenotypes under herbicide selection is a trueecological measure of resistance with implications for herbicide resistance evolution.