Paradigm Shift from Marker-Assisted Breeding to Genomics-Assisted Breeding for Calcium Nutrition in Finger Millet

The rapid advancements in molecular marker technologies followed by genomics, and next-generation sequencing technologies in major crops like rice, maize, and wheat have given opportunities for their use in the minor, but highly valuable future crops, including finger millet (Eleusine coracana (L.) Gaertn.). Finger millet, an orphan crop has an immense potential as a nutritional security crop due to its exceptionally high calcium content. Calcium (Ca), considered to be the most essential macronutrient, is required in relatively large quantities in the diet for maintaining healthy state of body. The unavailability of sufficient markers and genome sequence information in finger millet has resulted in limited breeding efforts for nutritional quality improvement through marker-assisted breeding. Nonetheless, advances in large-scale genomics technology have now streamlined production of genome-wide markers which can be used for large-scale identification of candidate genomic loci. The availability of NGS-based approaches with high resolution has enhanced the pace, precision, and efficiency of trait mapping. At present, trait-associated markers, cost-effective genotyping platforms and expertise are available for deploying genomics-assisted breeding in finger millet. High-throughput genotyping technology and phenotyping platforms have enabled genome-wide association studies, to precisely dissect the genetic architecture of complex traits such as calcium nutrition in finger millet. Large-scale mapping of agronomically important quantitative trait loci would not only help in the identification of molecular markers linked to grain calcium content in finger millet but also help in gene cloning and characterization, mining of elite alleles, exploitation of natural variations, and genomic selection paving the way toward genomics-assisted breeding, which ultimately will lead to genetic enhancement of finger millet. Therefore, marker-assisted breeding and selection is gradually evolving into ‘genomics-assisted breeding’ for crop improvement.