INTEGRATION OF SIMPLE SEQUENCE REPEAT DNA MARKERS INTO A SOYBEAN LINKAGE MAP

A total of 40 simple sequence repeat (SSR) or microsatellite DNA markers were mapped in a soybean [Glycine maw (L.) Merrill] mapping population that consisted of 60 F-2 plants from a cross between near isogenic Lines of the cultivars Clark and Harosoy. The first objective of study was to determine the map location of SSR loci in relation to 13 classical loci controlling pigmentation and morphological traits, seven isozyme loci, and a total of 118 RFLP and RAPD markers. The second objective was to determine if the microsatellite loci were randomly distributed in the soybean genome, Linkage analysis with MAPMAKER 3.0b yielded 29 linkage groups with a total map length of 1486 centimorgans (cM). This compares with a map length of 1056 cM if the SSR markers were removed from the data set. Thirty-four of the microsatellite loci were placed in linkage groups. SSR loci were linked to loci controlling nine of the 13 classical traits, and two of seven isozyme loci. Eighteen of the 29 linkage groups contained at least one SSR locus. While this result suggested that the microsatellite loci were randomly distributed throughout the soybean genome, two clusters of five and four SSR loci, spanning 23.4 and 33.6 cM, respectively, were detected. These results indicated a relatively limited amount of clustering of soybean SSR loci, and demonstrated that microsatellite genetic markers should provide an excellent complement to RFLP and RAPD markers for use in soybean molecular biology, genetics, and breeding research. Because SSR markers detect only single genetic loci and are highly polymorphic, they can be extremely informative in pedigree tracing studies, in the analysis of progeny from multiparent matings, in a wide range of mapping applications, and in genotype identification.