Classical and Molecular Genetic Mapping

A brief history of classical and molecular genetic mapping in soybean [Glycine max (L.) Merr.] is followed by a description of the most current version of the soybean genetic linkage map, which is primarily based on simple sequence repeat (SSR) or microsatellite markers as well as single nucleotide polymorphism (SNP) markers. Like many plant and animal species, the first molecular map of soybean was based on restriction fragment length polymorphism (RFLP) markers. Because of the relatively low level of sequence diversity in soybean, the first RFLP maps were constructed in populations derived from crosses of cultivated (G. max) × wild soybean [G. soja (Seib. et Zucc.)]. Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism loci were briefly used in map construction, but soybean was the first plant species in which SSR markers were employed and SSRs soon became the marker of choice in map development. SNP markers are now being widely used by plant and animal geneticists, and the most recent molecular genetic map of soybean incorporates a large number of SNPs from genic and nongenic regions.