Association mapping : a useful tool

Abstract

Future advances in plant genomics will make it possible to scan a genome for polymorphisms associated with qualitative and\rquantitative traits. Association mapping, also known as linkage disequilibrium mapping. Association mapping has the promise of\rhigher mapping resolution through exploitation of historical recombination events at the population level that may enable gene level\rmapping on non-model organisms where linkage-based approaches would not be feasible. Association mapping utilizes ancestral\rrecombinations and natural genetic diversity within a population to dissect quantitative traits and is built on the basis of the linkage\rdisequilibrium concept. One of the working definitions of linkage disequilibrium (which here on will be referred to as LD) is the nonrandom\rco-segregation of alleles at two loci. In contrast to linkage-based studies, LD-based genetic association studies offer a\rpotentially powerful approach for mapping causal genes with modest effects. The commonly used LD measure, D or D1 (standardized\rversion of D). Besides D, a various different measures of LD (D1, r2, D2, D*, F, X andd) have been developed to quantify LD.\rSoftwares packages measuring LD, such as “graphical overview of linkage disequilibrium” (GOLD), power marker, and TASSEL\r(Trait Analysis by association Evolution and Linkage) are available. Applications of AM has been extended from model plant\rarabidopsis to field crops. The increasing number of AM studies in crop species indicates the potential of this approach in all plant\rspecies in near future.