ABSTRACT
Gene mapping is a technique used to locate genes on a chromosome. It helps to determine the distance between genes and the molecular markers on chromosomes. This chapter explains in detail, the journey of gene mapping that starts with the experiments of Alfred Sturtevant (genetic mapping) and advancing under the knowledge of molecular markers, first-generation, next-generation, and third-generation sequencing techniques (physical mapping). The genera Gossypium includes 50 species which are rich sources of important genes for high yield, biotic and abiotic stress tolerance, and fiber quality. The position of these genes on chromosomes have been identified with the help of molecular markers including restriction fragment length polymorphism (RFLP), amplified fragment length polymorphism (AFLP), Simple sequence repeats (SSRs), expressed sequence tag (EST), randomly amplified polymorphic DNA (RAPD), etc. These molecular markers work on near-isogenic lines (NILs) and backcross populations to position the genes on chromosomes. With the help of these populations and molecular markers, the major genes controlling cotton yield, fiber quality, and stress tolerance have been positioned on A and D genomes.
