Competition between bird’s rape and canola in unmanaged field borders: Year 1.

Citation

Simard, M-J, Laforest, M., Martin, S. and Maheux, L. 2022. Competition between bird’s rape and canola in unmanaged field borders: Year 1. Weed Science Society of America/Canadian Weed Science Society meeting, February 22-24, Online. Poster

Résumé en langage clair

The most widely cultivated species of canola, Brassica napus, can be found as a weed in crops, field borders and roadsides. Bird’s rape mustard (Brassica rapa) is closely related to canola and can form fertile hybrids with crop plants. If both species grow together in a crop or a field border, the weedy B. rapa should progressively replace the domesticated B. napus. To document this process, both species were grown in unmanaged plots for three years. The experimental design was implemented twice (in 2019 and 2021) and included two B. napus cultivars, two wild B. rapa populations and a B. rapa cultivar. These populations were grown either isolated or with another cultivar/population (50% density). A total of 12 combinations tested. Growth stages were noted each week and biomass as well as seed production was evaluated at maturity. Statistical analyses included mixed ANOVA models. B. napus plants produced more biomass and bigger seeds than B. rapa, regardless of treatment combination. In general, the number of seeds produced was equivalent between crop plants and weeds and reduced in crop/weed combinations. There results indicate that if B. napus plants grow in a field border they can present equal fitness to B. rapa at the end of the growing season.

Résumé

The most widely cultivated species of canola, Brassica napus, can form volunteer populations in subsequent crops as well as transient feral populations in field borders and roadsides. Bird’s rape mustard (Brassica rapa) is closely related to Brassica napus and can form fertile hybrids with the crop that can backcross with parental lines. If both species grow together in a crop or a field border, the weedy B. rapa should show higher fitness and progressively replace domesticated B. napus. Meanwhile, hybrids and backcrossed plants will also be formed. To document this process, both species were grown in unmanaged plots for three years. The experimental design was implemented twice (in 2019 and 2021) and included two B. napus cultivars, two wild B. rapa populations and a B. rapa cultivar. These populations were grown either isolated or with another cultivar/population (50% density). A total of 12 combinations were replicated four times. Phenological stages were noted each week and biomass as well as seed production was evaluated at maturity. Statistical analyses included mixed ANOVA models. B. napus plants produced more biomass and bigger seeds than B. rapa, regardless of treatment combination. In general, the number of seeds produced was equivalent between crop plants and weeds and reduced in crop/weed combinations. There results indicate that if B. napus plants grow in a field border they can present equal fitness to B. rapa at the end of the growing season.