|DIWAN, NOA - UNIVERSITY OF MARYLAND
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/1997
Publication Date: N/A
Interpretive Summary: The development of a new soybean variety is an expensive process that requires a minimum of six years and requires extensive laboratory, greenhouse and field testing. Because of this large cost, public institutions and private industry seek protection of their investment through the Plant Variety Protection (PVP) Office of the USDA Agricultural Marketing Service. In order to obtain a PVP certificate, the developer of a new variety must demonstrate that it is different from all previously developed varieties. Up until now, the PVP Office has relied on standard pigmentation, morphological, and disease resistance traits to distinguish varieties. With ever increasing numbers of new varieties, the standard traits are no longer adequate to distinguish new varieties. In this report a new system of soybean variety identification is defined using Simple Sequence Repeat (SSR) DNA markers which are similar to those used in human identification. Using 20 newly identified soybean SSR DNA markers and an automated system to detect the size of fluorescently tagged DNA molecules, individual modern soybean varieties that are identical for morphological and pigmentation traits could be easily distinguished. This system can be used by developers of new soybean varieties to protect their varieties and will also be useful to soybean geneticists for pedigree analysis, population genetics studies and other basic genetic analyses.
Technical Abstract: Simple Sequence Repeat (SSR) allele sizing provides a useful tool for genotype identification, pedigree analysis, and for estimating genetic distance between organisms. Soybean [Glycine max (L.) Merr.] cultivars are identified for Plant Variety Protection (PVP) purposes by standard pigmentation and morphological traits. However, many commercial soybeans arise from a limited number of elite lines and are often indistinguishable based on these traits. A system based on SSR markers would provide unique DNA profiles of cultivars. In this work, a system was defined to assess genetic variability in soybean using allelic frequencies at 20 SSR loci in 35 soybean genotypes that account for greater than 95% of the alleles in North American soybean cultivars. Allele size in the 35 genotypes was determined using fluorescent labeled PCR products analyzed on a Perkin Elmer Prism 373A DNA Sequencer. An average of 10.1 alleles per locus (range: 5 to 17), with a mean gene diversity of 0.80 (range: 0.50 to 0.87) was observed at the 20 SSR loci. The 20 loci successfully distinguished modern soybean cultivars that are identical for morphological and pigmentation traits. Mutation rate of SSR alleles in soybean was similar to that reported in humans. To avoid any difficulty associated with mutation, DNA fingerprint data should be determined from the bulk of 30-50 plants of a cultivar.