Submitted to: Crop Science
Publication Type: Proceedings
Publication Acceptance Date: July 11, 1998
Publication Date: N/A
Interpretive Summary: Plant scientists throughout the world view the creation of molecular genetic linkage maps as high priority since these maps will provide plant breeders with the tools needed for rapid crop improvement. Such maps are the key to the discovery of molecular genetic markers that can be used to identify those progeny plants that carry superior characteristics. The first molecular linkage map of soybean, based upon Restriction Fragment Length Polymorphism (RFLP) markers, became available in 1991 and has since been updated a number of times. In this report a new generation of genetic map of the soybean is described that utilizes simple sequence repeat (SSR) markers, a new type of DNA marker that is now the marker of choice in human genetics research. It is the first such map available in a plant species. Over 400 SSR markers were developed at Beltsville, MD and mapped in three major soybean mapping populations. This is a collaborative effort involving g5 institutions and 10 scientists from across the US. SSR genetic markers are based upon the use of the polymerase chain reaction (PCR) technique that has revolutionized molecular biology. Unlike the previous versions of the soybean map, the new SSR-based map contains 20 linkage groups that correspond to the 20 sets of soybean chromosomes. This map and the markers it contains will be used by public and private soybean breeding programs for soybean improvement. It will be used by a range of soybean researches to determine the position of genes that control all aspects of soybean growth, development, disease resistance, quality, and seed yield.
A number of molecular genetic maps of the soybean [Glycine max (L.) Merrill] have been developed over the past 10 years. These maps are primarily based upon RFLP (restriction fragment length polymorphism) markers. In the soybean, RFLP markers generally have low levels of polymorphism and because soybean is an ancient polyploid, RFLP probes often hybridize and map to more than one position in the genome. Simple sequence repeat (SSR) markers possess high levels of genetic polymorphism and are developed as single locus makers and therefore provide a good alternative marker system in soybean. The objective of the work reported was the development and mapping of a large set of SSR markers. A total of 443 SSR loci were mapped in one or more of three populations: the USDA/Iowa State, G. max x G. soja F2 population; the Univ. of Utah, Minsoy x Noir 1 recombinant inbred population; and the Univ. of Nebraska, Clark x Harosoy F2 population. With a very few exceptions, SSR loci mapped to a single locus and the map order was essentially identical in each population. Because most SSR loci were mapped in more than one population it was relatively simple to align homologous linkage groups derived from the three populations. The resulting linkage map has 20 consensus linkage groups which most probably correspond to the 20 pairs of soybean chromosomes. All but one or perhaps two of the classical linkage groups are also assigned to their corresponding molecular linkage group.