Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/1996
Publication Date: N/A
Citation: Interpretive Summary: Heritable traits are found on genes on chromosomes. Soybean often has two or more copies of each gene, indicating that the chromosomes carrying those genes must be related to each other. The duplication of genes has interested plant breeders for many years because they might contribute to many important traits. In this paper the authors created maps of chromosomes and drew-out where duplicated genes were found. They found that over half of the major genes controlling the amount of seed protein and seed oil production in soybean are members of a duplicate gene family. This work tells us much about how breeders, when they select for specific traits, actually select to conserve many genes which may otherwise be lost. This work also helps us to predict where important genes may exist.
Technical Abstract: Restriction Fragment Length Polymorphism (RFLP) mapping data from nine separate populations (G. max X G. soja and G. max X G. max) of the Glycine subgenus soja genome has led to the identification of many duplicated segments of the genome. Linkage groups contained up to 33 markers that were duplicated on other linkage groups. The size of homoeologous regions spanned by three or more duplicated markers ranged from 8.7 cM to 107.6 cM, with an average size of 45.7 cM. One would expect to observe two sets of homoeologous sequences in a diploidized tetraploid, which the soybean has been assumed to be. However, we observed segments in the soybean genome that were present in as many as six copies with an average of 2.55 duplications per segment. Quantitative trait loci for seed protein and oil showed correspondence across homoeologous regions, suggesting that the genes or gene families contributing to these characters have retained similar functions throughout the evolution of the chromosomes. Many examples of duplicated segments nested within other duplicated segments were observed. These results suggest that at least one of the original genomes contributing to the polyploid genome of the glycine subgenus soja may have undergone an additional round of tetraploidization, and/or that large internal duplications in addition to tetraploidy are responsible for the highly duplicated nature of the genome of the subgenus. When the identification of all duplicated sequences is complete, saturation mapping of those segments should allow the transfer of map information from well-mapped to poorly-mapped regions of the genome.