Primary trisomics and SSR markers as tools to associate chromosomes with linkage groups in soybean

a complete set of primary trisomic individuals (each chromosome is trisomic in one member of the set) has Primary trisomics provide an excellent cytogenetic tool to associate allowed the establishment of cytogenetic maps. The trigenes and linkage groups with their respective chromosomes. A complete set of 20 primary trisomics (2x 1 41) has been established somic sets have been useful in positioning classical genes in soybean [Glycine max (L.) Merr.]. A linkage map of soybean with and molecular markers on specific chromosomes by the 20 consensus linkage groups has recently been defined. Because simple use of modified genetic ratios associated with trisomic sequence repeat (SSR) markers map to defined single positions in inheritance or by dosage effects from the extra chromothe soybean genome, the association of a SSR locus with a chromo- some (Tsuchiya, 1983; Carlson, 1988; Khush et al., 1984, some will provide an unambiguous association of a linkage group to McCouch et al., 1988; and Young et al., 1987). a specific chromosome. The objective of this work was to demonstrate In soybean [Glycine max (L.) Merr.], the complete the use of SSR markers to associate linkage groups with chromosomes set of primary trisomics (2x 1 41) has been difficult by means of primary trisomics. One population of F2 plants was devel- to establish because mitotic metaphase chromosomes oped from an F1 hybrid trisomic for chromosome 13 (Triplo 13) and are morphologically indistinguishable. Early attempts a second F2 population was obtained from a F1 hybrid trisomic for