Application of molecular markers to wheat breeding in Canada

Abstract

Marker-assisted breeding provides an opportunity for wheat breeders to introgress/pyramid genes of interest into breeding lines and to identify genes and/or quantitative trait loci in germplasm to be used as parents. Molecular markers were deployed to assist selection for disease resistance, agronomic and quality traits in several wheat cultivars released for commercial cultivation in Canada. Marker-assisted breeding is routinely used in most wheat breeding programmes for rust resistance (leaf, stem and stripe rust), orange wheat blossom midge resistance, high grain protein concentration, Fusarium head blight and common bunt resistance. Markers are being used selectively within breeding programmes to target traits that relate to market class or regional adaptation. For example, marker-assisted breeding for low lipoxygenase activity and low grain cadmium is being performed in durum breeding programmes and for enhancing stem solidness in programmes targeting resistance to the wheat stem sawfly. Markers are also being utilized for ergot resistance in durum wheat. Increased gluten strength is being selected with a marker for the overexpression of the Bx7 high-molecular-weight glutenin subunit. Marker-assisted breeding is also being used to pyramid resistance genes against a group of stem rust races related to TTKS (Ug99), a disease that poses a serious threat to global wheat production. Development of tightly linked diagnostic markers and high-throughput genotyping with SNP markers will result in more effective molecular wheat breeding in the near future and will open the door to genomic selection.

Advanced Breeding Strategies to Mitigate the Threat of Black Stem Rust of Wheat

“…The application of molecular markers has enabled breeders to select superior genotypes for traits that are difficult to select based solely on phenotype or to pyramid desirable combinations of genes into a single genetic background. MAB also offers the opportunity to improve response from selection because molecular markers can be applied earlier in the life cycle (for example gametic selection in the F1 seedling stage) (Randhawa et al, 2013). MAB not only contributes improved precision for selection of specific traits but is also costeffective compared with conventional plant breeding procedures.…”

“…have been cloned, and 97 functional markers have been developed to categorize 93 alleles based on gene sequences (Liu et al, 2012). Within traditional breeding systems, although MAB can be applied to all segregating generations, it is most commonly applied to early generations, including the F1 of complex crosses to enrich populations with favourable genes (Randhawa et al, 2013).…”

“…The molecular marker and gene of interest should be very closely linked, the marker needs to be validated to show trait association in the desired genetic backgrounds grown under target environments ) and the screening methodology should be cost-effective, time-saving and highly reproducible across laboratories (Randhawa et al, 2013). In Canada, wheat breeders, agronomists, pathologists and physiologists have given special emphasis to improving adaptation to biotic and abiotic stresses (ability to produce stable grain yield over locally variable environmental conditions), earliness and end-use quality of wheat.…”

“…tritici) and stripe rust (Puccinia striiformis); Fusarium head blight (FHB); and insects including wheat midge (Sitodiplosis mosellana G ehin) and wheat stem sawfly (Cephus cinctus Nort.) has been practiced routinely in wheat breeding programmes (Randhawa et al, 2013). The application of doubled haploid (DH) technology in wheat breeding programmes has increased the speed of cultivar development, particularly in winter wheat, where use of contra-season nurseries to achieve two breeding cycles per year is not possible.…”

“…Wheat breeders screen parental plants for various alleles before DH production and haploid plants are subjected to marker assisted selection prior to chromosome doubling to ensure the retention of gene(s) of interest and to discard undesirable genotypes. (Randhawa et al, 2013).…”