Linkage disequilibrium mapping: A journey from traditional breeding to molecular breeding in crop plants

Abstract

Germplasms are the reservoir of agronomically important traits traditionally maintained by various tribal communities over the year. Maintaining these germplasms generations after generations has little value unless exploited for the desired agronomic traits like biotic and abiotic stress, yield attributes and nutritional enrichment. Association mapping, otherwise called linkage disequilibrium mapping, is a molecular breeding approach for characterizing complex traits with agronomic importance in crop plants. It is a systematic method for identifying novel traits and is treated as an alternative tool to traditional QTL mapping approaches, which involves correlating molecular markers with the phenotypic trait in a diversified population. The map's resolution in association mapping is based on the candidate-gene approach or genome-wide association approach. Therefore, association mapping studies offer a great perspective on crop genetic improvement. Still, considerably large-scale research is required to determine the sensible implementation of association mapping analysis in most crop plants. Currently, there is considerable interest in using association mapping approaches in crop breeding programs, which can be achieved by advanced genomic technology and the development of statistical computer software packages. Here, the linkage disequilibrium approach and its usefulness in association mapping studies, including the steps associated with it are discussed. The current status and future challenges in complex trait dissection by utilizing the linkage disequilibrium mapping in crop plants are also discussed.