Fusarium Head Blight in Canadian Winter Wheat: Utilizing Association Mapping and Genomic Selection for Resistance Breeding
Fusarium Head Blight (FHB) is a devastating disease of Wheat (Triticum aestivum L.) caused primarily by Fusarium graminearum Schwabe in Canada. Wheat FHB results in yield and produce quality losses. The clearest symptoms of FHB are premature bleaching of spikelets in the field, and fusarium damaged kernels in the harvested seed. Insufficient and costly disease control strategies make breeding for FHB resistance in wheat an ideal choice. There is a lack of FHB resistance sources in the Canadian wheat germplasm and Genome Wide Association Studies (GWAS) can be utilized to identify such sources. Furthermore, as no Quantitative Trait Loci (QTL) provides absolute resistance to FHB, identification of novel sources of resistance is desired. Genomic Selection (GS) has great potential in crop improvement, specifically for quantitative traits. A diversity panel that represents the genetic diversity of the Canadian, i.e., high latitude North American winter wheat was assembled for this thesis and the genetic diversity, population structure, and linkage disequilibrium of the germplasm was studied. To identify QTL associated with FHB, a GWAS study was conducted using the phenotypic data collected at three locations over two years. For understanding the role of number of genotypic markers, population structure, and choice of model in trait prediction modelling, a GS study was conducted. The Canadian Winter Wheat Diversity Panel is a diverse collection of winter wheat capturing diversity both in time and geography from Canada. The panel comprises of seven subpopulations with different LD, allele frequencies, and genetic diversity parameters. Multiple QTL associated with FHB related traits were identified on 13 chromosomes which may harbor genes involved in plant defense and stress response mechanisms. For FHB resistance improvement, the GS study demonstrated that the modelling parameters can be determined based upon the genotypic information available. Deoxynivalenol contamination was one of the traits with the highest prediction accuracy. GS can account for minor effect QTL, which is beneficial when breeding for quantitative traits. FHB resistant varieties are needed for an effective and economical disease control strategy in wheat and GS can complement current breeding efforts to develop FHB resistant wheat varieties.