Molecular mapping, marker-assisted selection and MAP-based cloning in tomato

Significant progress has been made in molecular marker research in tomato, Lycopersicon esculentum Mill., including generation of markers, development of maps, mapping of genes and QTLs, and fine-mapping, characterization and map-based cloning of genes and QTLs. Numerous types of molecular markers have been developed in tomato, including RFLPs, RAPDs, AFLPs, SSRs, CAPS, ESTs, COSs and SNPs. Several molecular maps of tomato have been developed based on different interspecific populations, including the saturated linkage map based on a L. esculentum × L. pennellii cross. Markers and maps have been utilized extensively to map genes and QTLs controlling agriculturally and biologically important traits and for marker-assisted improvement of many simple-inherited traits such as disease resistance. Marker information also has been used for fine mapping and map-based cloning of several major genes and QTLs. Comparatively, little progress has been made in improving complex traits via marker-assisted selection. However, rapid advances in developing more efficient and resolving markers and in refining QTL positions are expected to lead to a greater use of marker technology for crop improvement in tomato.