Assessing Bipyridylium Resistance in Canada Fleabane (Conyza canadensis (L.) Cronq.)
Canada Fleabane (Conyza canadensis) is an economically important, resistant weed species. The objective of the study was to characterize paraquat and diquat resistance in geographically isolated, evolutionarily unique biotypes of C. canadensis, 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. Results indicated F2 families deviated from expected 3:1 ratio for resistance to paraquat, indicating that resistance in C. canadensis was not attributable to single gene inheritance. Evaluated digenic models suggested an 11:5 ratio may best describe paraquat resistance. These results are some of the first to evaluate impacts of herbicide resistance on expression of transgressive segregation. F2 progeny from the paraquat RxS cross demonstrated transgressive segregation at discriminating and parental eliminating doses. Transgressive segregation was not observed in progeny from a paraquat RxR cross.