Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Arts

First Advisor

Zhongwei Zou

Advisor Role

Supervisor

Abstract

Sclerotinia Stem Rot (SSR), caused by Sclerotinia sclerotiorum, poses a significant threat to canola (Brassica napus), which is crucial for Canada's agricultural economy. This disease can lead to drastic yield losses and adversely affect seed quality, impacting export values. Current management strategies mainly rely heavily on fungicides application, which is known to have adverse effect on environment, and generates fungicide resistance. Since there is limited resistance against S. sclerotiorum in canola, it is urgent to identify effective genetic resistance that can be introduced to breeding programs. The objectives of this project were to investigate quantitative resistance to SSR in canola by identifying candidate defence-associated genes, with a focus on valine-glutamine (VQ) genes, and to functionally evaluate the potential role of BnMKS1 in enhancing SSR resistance. Various canola genotypes were screened for enhanced SSR resistance using ex-vivo mycelial agar plug inoculation. Quinta and 1065 genotypes exhibited the greatest susceptibility, while Surpass and Jet Neuf genotypes demonstrated the strongest resistance. Transcriptome analysis of the resistant cultivar Jet Neuf identified numerous genes associated with the defence response, including members of the VQ gene family. Genome-wide characterisation identified 124 VQ genes in B. napus, including 15 previously unclassified genes. Expression analyses revealed differential regulation of several VQ genes following infection, highlighting candidate positive and negative regulators of plant immunity and identifying promising targets for future functional studies. To investigate the role of the VQ gene, MKS1, transgenic B. napus lines overexpressing BnMKS1 were evaluated following S. sclerotiorum infection. Overexpression of BnMKS1 provided evidence of enhanced defence during the early stages of infection; however, this effect diminished as disease progressed, suggesting that its contribution to quantitative resistance is limited. Although trends in defence-related gene expression were observed, further functional validation is required to clarify the roles of BnMKS1 and other candidate genes. Overall, this work advances the understanding of gene function underlying quantitative resistance to S. sclerotiorum in canola. By integrating disease phenotyping and transcriptomics, this research identified novel candidate resistance genes and provides a foundation for future studies aimed at developing canola cultivars with improved resistance to SSR.

Convocation Year

2026

Convocation Season

Fall

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