Linkage Disequilibrium Mapping As an Advancement in Crop Breeding

Abstract

Mini Review Adv Plants Agric Res 2017, 6(2): 00207 generations to link phenotypes (observable characteristics) with genotypes (genetic constitution) in large germplasm populations. It is a powerful genetic mapping tool for crops and provides high-resolution, broad allele coverage, and cost-effective gene tagging for the evaluation of plant germplasm resources. Concept of Linkage Disequilibrium Mapping Association mapping is based on the principle that over several generations of recombination, correlations of linked markers with trait of interest will remain. Therefore, spurious associations between genotype and trait may be detected due to the degree of structure within the population, necessitating development of various statistical methods to account for population structure [2,3]. Association mapping give surety of high resolution mapping by exploitation of historical recombination events at the population level that may enable gene level mapping on non-model organisms where linkage-based approaches would not be feasible. Potential exploit of such approach could be for fine mapping of genes / QTLs, identifying favorable alleles for marker assisted selection and cross validation of outcome from linkage mapping for accurate position of genes / QTLs of interest [4]. Genetic mapping of QTLs can be performed in two main ways: a. Linkage analysis based mapping or conventional mapping using experimental populations or bi-parental mapping populations and b. Linkage disequilibrium based mapping or " association mapping " using diverse lines from the natural populations or germplasm collections or landraces. Linkage based QTL mapping can identify the related genes to biparental variations so that mapping resolution depends on the number of recombinations occurred in the process of the development of mapping populations. Furthermore, construction of a suitable mapping population for study is very time consuming. Association mapping has recently become popular for identifying and mapping QTLs with high resolution. Linkage disequilibrium (LD) based association mapping can lead to the most effective utilization of ex-situ conserved natural genetic diversity or germplasm resources of crop plants.