Gel Based DNA Marker Technologies in Cotton

Genetic mapping with DNA markers has become an essential tool for revealing the genetic basis of both qualitative and quantitative traits in crop plants. DNA markers have special advantages over morphological traits in genetic analysis because they are normally polymorphic, have no pleiotropic or epistatic effects, employ non-destructive methods requiring very small amounts of plant materials and there is no effect of environment on the phenotype. Many of the economically important traits of crop plants are controlled by complex quantitative traits (QTL). An accurate and detailed genetic map of DNA markers linked to QTLs provides an invaluable tool to the breeders to use molecular markers in marker-assisted selection by allowing selection for the markers rather than the complex QTL phenotype. Recently several laboratories in USA and abroad have launched special initiatives on molecular genome mapping programs in cotton to exploit the available gene pools and enhance the improved germplasm resources (Cantrell et al., 1999; Yu and Kohel 1999; Rungis et al. 1999; Cantrell et al., 1998, 1999; He et al. 1999; Wright et al. 1998; Luo et al. 1999; Akbari and Lyon, 1999).