Biofortifying Brassica with calcium (Ca) and magnesium (Mg)

Billions of people worldwide consume insufficient calcium (Ca) or magnesium (Mg) for adequate health. Dietary Ca and Mg intakes can potentially be increased through crop biofortification. Recently, we reported sufficient natural genetic variation and heritability in a leafy crop plant (Brassica oleracea; C-genome, 1n=9; cabbage, cauliflower, kale etc.) to indicate that genetic biofortification is feasible in vegetable Brassica. We also reported loci affecting shoot Ca and Mg concentration (shoot-Ca and Mg). Here, we extend the previous study to explore the closely related species B. rapa (A-genome, 1n=10; Chinese cabbage, pak choi, a more tractable species genetically, and the amphidiploid species B. napus(AC-genome, 1n=19; canola/oilseed rape etc.). Wide variation in shoot/leaf-Ca and Mg occurs among all three species. Shoot/leaf-Ca and Mg is significantly and highly heritable. Quantitative trait loci (QTL) affecting shoot/leaf Ca and Mg concentration occur in potentially paralogous regions of B. oleracea and B. rapa. If confirmed, allelic variation at such loci could be used in biofortification breeding programs for vegetable Brassica. As genome sequencing and marker generation improves, it will be possible to resolve these (and other) putative loci to the gene level. Further studies on the regulation, interaction and function of these genes will enable us to understand Ca and Mg dynamics in plants.