Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Zhongwei Zou

Advisor Role

Supervision, Funding

Second Advisor

Dilantha Fernando

Advisor Role

Supervision

Abstract

Canola (Brassica napus) is one of the world's most important oilseed crops. Verticillium stripe, caused by the soil-borne fungus Verticillium longisporum, has recently emerged as a potential threat to domestic canola production. As severity increases, the disease can cause yield losses of up to 80% per plant. Because V. longisporum was recently detected in Canada, understanding resistance in Canadian canola cultivars is limited. Blackleg, primarily caused by the fungal pathogen Leptosphaeria maculans, also causes significant yield losses in canola. In the field, the two diseases may co-occur in canola. Although the resistance of canola to blackleg is well studied, how Verticillium stripe affects this resistance remains unclear. This project investigated the interaction between L. maculans and V. longisporum in canola through phenotypic assessment of disease severity (DS) and evaluated the role of BnWRKY33 in disease resistance to Verticillium stripe. To understand the interaction between the two pathogens, canola genotypes carrying different Rlm (resistance to L. maculans) genes, along with Westar (no Rlm genes), were inoculated with both L. maculans and V. longisporum under greenhouse conditions. DS evaluation showed that genotype 01-23-2-1 showed greater resistance to Verticillium stripe at the rosette stage than Westar, while Quinta and Jet Neuf were more susceptible. Inoculation with both pathogens increased Verticillium stripe and blackleg severity in the tested genotypes at the adult stage, suggesting a possible synergistic interaction between V. longisporum and L. maculans. To assess the role of the BnWRKY33 gene in B. napus resistance against V. longisporum, transgenic lines overexpressing BnWRKY33 were assessed following V. longisporum infection. At the early infection stage, disease severity assessment revealed that BnWRKY33 overexpression showed increased resistance to Verticillium stripe. Although defense-related gene expression analysis supported this finding, further validation is required to clarify the role of BnWRKY33 in host resistance. These preliminary findings lay the groundwork for investigating the genetic basis of the interaction between V. longisporum and L. maculans with the host through transcriptomic analysis. This approach will help identify potential genes that influence Verticillium stripe resistance in the host and support future breeding efforts.

Convocation Year

2027

Convocation Season

Spring

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