The influence of ambient environment on the growth and fitness of glyphosate-resistant and -susceptible giant ragweed (Ambrosia trifida L.) biotypes

Author

Julia A. Thompson, The University of Western OntarioFollow

Degree

Master of Science

Program

Biology

Supervisor

Dr. Robert Nurse

Abstract

Glyphosate-resistant giant ragweed can be found in agricultural fields throughout the mid-western United States and southwestern Ontario. Environmental factors can influence growth and herbicide efficacy in C₃ plant species. I measured the aboveground injury to resistant and susceptible seedlings for 28 d following glyphosate treatment to test the hypothesis that young leaf stages would be more susceptible to glyphosate under warm, dry, low-CO₂ conditions. Glyphosate-resistance was not affected by environmental factors, leaf stage, or glyphosate dose, but plants grown at the highest temperature after spray had the least glyphosate injury. Resistant alleles may be associated with fitness penalties because they are rare in populations without herbicide selection pressures; however, in a greenhouse trial, resistant biotypes recovered from glyphosate injury and produced seeds. My results suggest that potentially stressful growth conditions and treatment at young growth stages will not improve the control of resistant giant ragweed biotypes.

Recommended Citation

Thompson, Julia A., "The influence of ambient environment on the growth and fitness of glyphosate-resistant and -susceptible giant ragweed (Ambrosia trifida L.) biotypes" (2012). Electronic Thesis and Dissertation Repository. 414.
https://ir.lib.uwo.ca/etd/414