Principles, requirements and prospects of genetic mapping in plants

Genetic mapping (also known as linkage mapping or meiotic mapping) refers to the determination of the relative position and distances between markers along chromosomes. Genetic map distances between two markers are defined as the mean number of recombination events, involving a given chromatid, in that region per meiosis. Genetic map construction requires that the researcher develop appropriate mapping population, decide the sample size and type of molecular marker(s) for genotyping, genotype the mapping population with sufficient number of markers, and perform linkage analyses using statistical programs. The construction of detailed genetic maps with high levels of genome coverage is a first step for localizing genes or quantitative trait loci (QTL) that are associated with economically important traits, marker assisted selection, comparative mapping between different species, a framework for anchoring physical maps, and the basis for map-based cloning of genes. Highly reproducible, high throughput, codominant, and transferable molecular markers, especially developed from expressed regions, are sought to increase the utility of genetic maps. This article reviews the principles, requirements, and future prospects of genetic mapping in plants.