Phenotypic and genotypic investigation of the seed storage protein cruciferin in Brassica napus L.
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World-wide, there is an increasing demand for sources of high-quality protein, resulting in an interest in novel plant-based proteins. Canola (Brassica napus L.) is the second greatest produced oilseed crop worldwide, and a crop of high importance to the Canadian economy. Brassica napus meal is primarily used as a source of protein in livestock feed but may serve as a source of plant-based proteins for human consumption. The seed storage protein cruciferin makes up approximately 60% of the protein content of mature seeds and is of interest due to its functional properties. In order to optimize B. napus cruciferin protein profiles, plant breeding efforts require a thorough understanding of existing phenotypic variation in cruciferin content, as well as insight into the effect of genotype and environmental factors on this trait. This study used an enzyme-linked immunosorbent assay (ELISA)-based approach to determine cruciferin content in a diverse population of B. napus genotypes. Considerable variation in cruciferin content was observed, and the effects of genotype by site-year interactions were shown to significantly affect cruciferin content. Future breeding efforts will also require efficient methods to determine cruciferin content, and for this reason the suitability of near-infrared spectroscopy (NIRS) as a potential method was explored. Combining reference data provided from the ELISA-based quantification method with spectra produced by scanning whole seed samples of B. napus enabled the development of several NIRS calibration equations. Unfortunately, statistical analysis showed that these equations were poorly suited for the prediction of cruciferin content. Finally, a genome-wide association study (GWAS) was performed to provide a more thorough understanding of the genetic control of cruciferin content. A population of 51 B. napus genotypes was used for GWAS, which identified 144 SNP-trait associations across 47 loci significantly associated with cruciferin content. Based on these loci, 11 candidate genes were identified as having a potential role in the genetic control of cruciferin content. This research provides a background on existing phenotypic variation and the genetic control of cruciferin content, building a valuable framework on which future efforts to develop B. napus with specialty protein profiles may be based.
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