GENETIC-MAPPING AND VARIABILITY OF 7 SOYBEAN SIMPLE SEQUENCE REPEAT LOCI

Microsatellites or simple sequence repeats are stretches of short tand emly repeated DNA sequence motifs, dispersed throughout the genomes of most eukaryotes. Simple sequence repeat polymorphisms (SSRPs) have re cently been reported in plants. Here we present the genetic map positi on of seven different soybean (Glycine max (L.) Merr. and Glycine soja Sieb. and Zucc.) SSRPs contained in sequenced genes, four of which re present newly mapped positions for these genes. The other three SSRPs coincided with independently established RFLP map positions for the co rresponding genes. When a set of 61 soybean accessions was screened at four of these loci by using agarose gels, the average number of allel es per locus was 7.75, the effective number of alleles (n(e)) was 2.57 , and the level of allele differentiation (delta(T)) was 0.62. Allelic variation decreased sharply with increasing levels of domestication, with the level of differentiation going from 84% in the wild soybean t o 43% in the elite germplasm. Variation levels observed on a subset ma de of 19 of the 61 lines were always higher for SSRPs than for RFLP ma rkers, with the average number of alleles per locus going from 4.25 to 2.15. In comparison with RFLP markers, SSRPs are more informative and are easier to analyse but require more effort to develop.