A Multi-omics approach for genetic and molecular analysis of clubroot resistance in Brassica napus canola
Creators: Kaur, Kawalpreet
Publisher: name: University of Alberta Library
Year: 2023

<p>Clubroot disease, caused by Plasmodiophora brassicae, is a significant threat to canola production. Growing of clubroot resistant canola cultivars is the most efficient and environment-friendly way of managing this disease. The evolution of new pathotypes eroded some of the resistance available in canola. This necessitates the finding of new resistance and introgression into canola. In this PhD thesis research, clubroot resistance of the European fodder turnip cv. Debra (ECD 01) was introgressed into B. napus canola through interspecific hybridization between these two species, and an advanced generation of B. napus canola recombinant inbred line (RIL) population (BC1F8) was developed. This population carried resistance to multiple pathotypes including pathotype 3H, 3A, 2B and 5X. Whole-genome resequencing of the RILs carrying resistance to pathotype 3H or 3A was performed to identify the genomic regions contributing to clubroot resistance. Based on this finding, and through different QTL mapping approaches, three genomic regions located at 1-4 Mb region of the chromosome A02, 0.98-2.0 Mb region of A03 and 38.01-41.5 Mb region of A09 were identified showing resistance to pathotype 3; among these, the A09 locus exerted the greatest contribution for resistance to pathotype 3A.<br>
    To understand the molecular basis of the Debra-resistance in canola, near-isogenic clubroot resistant and susceptible lines were developed based on this resistance and were used for transcriptome and proteome analysis. These analyses identified several putative genes/proteins related to cell surface receptors (receptor-like kinases, receptor-like proteins), phytohormone signalling (auxin, salicyclic acid, jasmonic acid), calcium-mediated signalling (calmodulin-gated calcium channels, calcium-dependent protein kinases), reactive oxygen species, glucosinolate biosynthesis pathway as well as genes/proteins related to disease resistance. <br>
    In addition to this, an investigation on the C2H2-zinc finger protein coding genes (transcription factors) of the B. napus genome was carried out. This study identified 267 genes carrying cis-acting elements in their promoter regions; and all these genes showed distribution across the 19 chromosomes of B. napus. Expression analysis of 20 C2H2-zinc finger genes demonstrated that this class of genes are involved in defense response against abiotic and biotic stresses, including clubroot disease. This analysis further demonstrated that some of the genes may be involved in defense response against multiple stresses and in response to more than one phytohormones. <br>
    Thus, this thesis research provided solid evidence that the clubroot resistance of the turnip accession ECD 01 can be used for broadening the genetic base of clubroot resistance in B. napus canola for durable resistance to this disease. The multi-omics approaches applied in this research helped in the identification of the genomic regions, genes and proteins playing a role in the molecular mechanisms involved in clubroot resistance. These results also suggested that the C2H2-zinc finger genes can be targeted for the improvement of stress tolerance in canola.  </p>