Evaluation of Bioherbicidal Properties of Pseudomonas syringae pv. tagetis for Control of Canada thistle (Cirsium arvense)

Canada thistle (Cirsium arvense, family Asteraceae) is a particularly aggressive invasive plant species that is problematic in Canadian agriculture. It can be particularly challenging for organic farmers, as it cannot be eliminated using methods like tillage, due to its ability to regrow using adventitious shoots from root fragments. One strategy would be to use an organic bioherbicide. One bacterial pathogen that has been explored as a replacement for conventional herbicides is Pseudomonas syringae pv. tagetis, as it produces tagetitoxin, which causes chlorosis and stunting in plants of the Asteraceae. The objective of my thesis was to assess P. syringae pv. tagetis strains for use as an organic bioherbicide for Canada thistle. There were four objectives in this study: 1) to assess the virulence of P. syringae strains in sunflower (Helianthus annuus); 2) to evaluate the top candidate strains in Canada thistle (Cirsium arvense); 3) to determine the lowest infectious dose; and 4) to perform general characterization of P. syringae pv. tagetis. Assays of 32 P. syringae strains showed five pathovar tagetis strains (4091, 6564, 6370, 6371, and 11161) exhibiting potential to cause chlorosis, stunt growth and reduce biomass of sunflower, a plant in the target plant family, Asteraceae, which past studies have shown are affected similarly to Canada thistle. The effects of the leading strains in Canada thistle were similar to the results in sunflower in terms of chlorosis, increases in exposed soil, and reduction of biomass. The minimum infectious dose of P. syringae pv. tagetis 6371 was 1x109 cfu/mL in sunflowers and similar in Canada thistle. Finally, it was found that strains 6370, 6371 and 6564 had some negative effects on plants in the family Brassicaceae in terms of chlorosis, reducing healthy tissue, and reducing leaf biomass of plants. These results indicate the potential of P. syringae pv. tagetis for future use as a bioherbicide in organic agriculture.

Name thesis:degree_name

Master of Science (MSc)

Level thesis:degree_level

Master's

Discipline thesis:degree_discipline

Biology

Grantor dc:publisher

Faculty of Graduate Studies and Research, University of Regina

Year dc:date.issued

2020

Author dc:creator

• Cameron, Alexander John

Advisor dc:contributor.advisor

• Stavrinides, John

Committee member dc:contributor.committeemember

• Weger, Harold

Language dc:language.iso

en

DOI

https://doi.org/10.82465/4171

OAI identifier oai:identifier

oai:uregina.scholaris.ca:10294/14326