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Confirmation and mechanism of resistance to glyphosate in giant ragweed (Ambrosia trifida) in Ontario

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Title: Confirmation and mechanism of resistance to glyphosate in giant ragweed (Ambrosia trifida) in Ontario
Author: Green, Amanda C.
Department: Department of Plant Agriculture
Program: Plant Agriculture
Advisor: Tardif, François J.Sikkema, Peter H.
Abstract: The basis of resistance to glyphosate in two giant ragweed populations exhibiting different phenotypic responses to glyphosate is unknown. Population R1 exhibits a rapid necrosis of mature leaves followed by eventual regrowth of young tissue while population R2 shows general chlorosis and cessation of growth followed by growth in 21 to 28 days. The objectives were to determine the resistance index of the two populations and investigate mechanisms of resistance. The resistance index, based on LD50 values, was 16 and 19 for R1 and R2, respectively. Accumulation of shikimate in leaf discs (an indicator of glyphosate target site sensitivity) occurred at lower glyphosate doses for S populations than in R1 and R2 suggesting differential target site inhibition. [14C]-glyphosate was used to measure absorption and translocation. Absorption levels of R1 and susceptible populations were similar. Less [14C]-glyphosate was translocated to the roots and above the treated leaf in the R1 population.
URI: http://hdl.handle.net/10214/8330
Date: 2014
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