Interested Members of the University Community are invited to attend the Final Oral Examination for the Degree of Master of Science of Hayley Hickmott of the Department of Plant Agriculture 

Date: Monday, March 14, 2022
Time: 10:00am
Method: Via Zoom
Join Zoom Meeting: https://zoom.us/j/91826562561?pwd=b2hvTkR2c2xVbFczU2hOTEM0MlJRZz09
Meeting ID: 918 2656 2561
Meeting Password: 578207 

Thesis Title: Assessing Bipyridylium Herbicide Resistance in Conyza canadensis (L.) Cronq. 

Advisory Committee
Dr. François Tardif (Advisor)
Dr. Eric Page (Co-advisor)
Dr. Istvan Rajcan                                                           

Examination Committee
Chair: Dr. Manish Raizada
Dr. François Tardif
Dr. Eric Page
Dr. Martin Laforest                                          

ABSTRACT 

Canada Fleabane (Conyza canadensis) is an economically important weed species prone to developing herbicide resistance. The objective of this study was to characterize paraquat and diquat resistance in geographically isolated biotypes of C. canadensis, whose resistance traits represent unique evolutionary events and evaluate inheritance using segregating F2 families. Resistant (R) biotypes were crossed to a common susceptible (S), and amongst themselves. Discriminating and parental eliminating doses of paraquat and diquat were identified through dose responses for each cross. Results indicated F2 families deviated from the expected 3:1 ratio for resistance to paraquat, indicating that resistance in C. canadensis was not attributable to single major gene inheritance. Digenic models were evaluated; results suggested an 11:5 ratio may best describe paraquat resistance in C. canadensis. Results of this research are some of the first to evaluate the impact of herbicide resistance on expression of transgressive segregation. F2 progeny from the cross of a paraquat RxS biotype demonstrated transgressive segregation at discriminating and parental eliminating doses. Transgressive segregation was not observed in progeny from a cross of two paraquat R biotypes, suggesting that evolution and selection for resistance may impact expression.