|Sleper, David - UNIVERSITY OF MISSOURI|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 10, 2005
Publication Date: February 24, 2006
Citation: Beuselinck, P.R., Sleper, D.A., Bilyeu, K.D. 2006. An assessment of phenotype selection for linolenic acid in soybean using genetic markers. Crop Science. 46:747-750. Interpretive Summary: More soybeans are produced than any other legume crop in the world. Soybeans have value from their high protein meal and abundant oil. Typically, soybean oil consists of undesirably high amounts of linolenic acid. There are soybean lines that have lower linolenic acid, but breeding for low linolenic acid soybeans is complicated by the complex nature of the trait. We have developed molecular markers that distinguish mutant genes for low linolenic acid from their wild-type counterparts as tools in breeding programs. We analyzed progeny from crosses between low linolenic and wild-type soybean lines that were selected and advanced using phenotypic criteria, before the molecular markers had been available. The molecular markers allowed us to perform a retrospective assessment of the effectiveness of breeding selections that were based on chemical phenotype. We discovered that selecting for low linolenic by chemical phenotype allowed less desirable genotypes to advance to the next generation of selection or development. Allowing less desirable genotypes to advance to the next level in the breeding cycle further complicates selection and adds layers of testing and evaluation. The molecular markers can make soybean breeding more efficient by identifying desirable genotypes before crossing and selecting progenies by genotype to fix the low linolenic trait. This research will promote the efficient breeding of soybean varieties for low linolenic acid and will benefit soybean producers and processors.
Technical Abstract: Three independent genetic loci have been shown to contribute to soybean Glycine max (L.) Merrill seed linolenic acid levels. Objective of this study was to assess the accuracy of phenotypic selection for low seed linolenic acid in soybean using molecular markers for mutations in two fatty acid desaturase genes, GmFAD3A and GmFAD3C. Molecular markers allowed a retrospective evaluation of the effectiveness of selections based on chemical phenotype. The low linolenic acid soybean line CX1512-44 was crossed with two experimental breeding lines. Genotyped F4 progeny were derived from 65 F3 plants that were selected for low seed linolenic acid content. Genotyping for GmFAD3A and GmFAD3C was successful in 57 of the 65 F4 progeny rows. Five of 8 possible genotypes were recovered. Thirty-nine of the 57 F4 progeny rows were homozygous for two FAD3 mutants (aacc), while the remaining progeny rows were heterozygous or homozygous wild-type. Approximately 22% of the heterozygous F4 progeny fell within the selection criteria for low linolenic acid, <35 g/kg oil. Sixteen lines derived from low linolenic acid progenies were evaluated for yield; 13 were homozygous mutant (aacc) and 3 were heterozygous (aaCc). Advancing the heterozygotes constituted an error of approximately 19%. Use of molecular markers for GmFAD3A and GmFAD3C can eliminate heterozygotes from advancing to the next generation of selection or development.