New Sources of Soybean Seed Meal and Oil Composition Traits Identified Through TILLING

Authors: DIERKING, EMILY - University Of Missouri; Bilyeu, Kristin

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2009
Publication Date: 7/14/2009
Citation: Dierking, E., Bilyeu, K.D. 2009. New Sources of Soybean Seed Meal and Oil Composition Traits Identified Through TILLING. Biomed Central (BMC) Plant Biology. 9(1):89.

Interpretive Summary: A new genetics approach which takes advantage of accumulated gene knowledge in model plants and also in soybeans has been utilized to identify novel mutations in soybean genes that control important seed composition traits. Soybean raffinose synthase genes and microsomal omega-6 fatty acid desaturase genes were screened for novel alleles in mutagenized soybean populations. New soybean lines were identified with mutations in two sobyean seed composition genes that slightly alter normal development in soybean seeds. These alterations cause positive changes in seed energy content and fatty acid profiles of the oil, important traits to increase the nutritional aspects of soyean meal that is included in livestock diets and also to increase the amount of heart-healthy mono-unsaturated fatty acids that are present in soybean oil. New technology was developed to reliably detect the inheritance of the mutant genes and can be used in efficient development of new soybean varieties with the desired seed composition traits. The impact of this research is new sources of germplasm and gentoyping tools to accelerate soybean breeding for improved soybean seed composition traits.

Technical Abstract: Background: Several techniques are available to study gene function, but many are less than ideal for soybean. Reverse genetics, a relatively new approach, can be utilized to identify novel mutations in candidate genes; this technique has not produced an allelic variant with a confirmed phenotype in soybean. Soybean raffinose synthase genes and microsomal omega-6 fatty acid desaturase genes were screened for novel alleles in mutagenized soybean populations. Results: Four mutations in independent lines were identified in the raffinose synthase gene RS2; two mutations resulted in amino acid mutations and one resulted in an altered seed oligosaccharide phenotype. The resulting phenotype was an increase in seed sucrose levels as well as a decrease in both raffinose and stachyose seed oligosaccharide levels. Three mutations in independent lines were identified in the omega-6 fatty acid desaturase gene FAD2-1A; all three mutations resulted in missense amino acid mutations and one resulted in an altered seed fatty acid profile that led to an increase in oleic acid and a decrease in linoleic acid in the seed oil. Conclusions: The oligosaccharide phenotype controlled by the novel RS2 allele is similar to previously observed seed oligosaccharide phenotypes in RS2 mutant (PI 200508) allele-containing lines. Due to the anti-nutritional characteristics of raffinose and stachyose, this represents a positive change in seed composition. The fatty acid phenotype controlled by the novel FAD2-1A allele controls an increase in oleic acid in the seed oil, a phenotype also observed in a line previously characterized to have a null allele of the FAD2-1A gene. Molecular marker assays were developed to reliably detect the inheritance of the mutant alleles and can be used in efficient breeding for these desired seed phenotypes. Our results serve as the first demonstration of the identification of soybean mutants controlling seed phenotypes discovered through the reverse genetics technique TILLING.feed which require less nutrient supplementation, are more nutritious, and are more environmentally friendly.