Environmental stability of seed carbohydrate profiles in soybeans containing different alleles of the raffinose synthase 2 (RS2) gene

Authors: Bilyeu, Kristin; WIEBOLD, WILLIAM - University Of Missouri

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2016
Publication Date: 2/10/2016
Publication URL: http://handle.nal.usda.gov/10113/62181
Citation: Bilyeu, K.D., Wiebold, W.J. 2016. Environmental stability of seed carbohydrate profiles in soybeans containing different alleles of the raffinose synthase 2 (RS2) gene. Journal of Agricultural and Food Chemistry. 64:1071-1078.

Interpretive Summary: Soybean meal is the most important source of protein for livestock feeds in the US. When soybean meal is processed, soluble sugars are present in the product, but some of those sugars are nutritionally beneficial while others are considered anti-nutritional because they are not utilized for energy. We have identified different soybean lines that have potentially improved nutritional qualities in their sugar profiles. The objective of this work was to characterize the variation in those sugar profiles for the soybean lines grown at different locations in Missouri and with different planting regimes to change the environment tin which seeds are produced. We defined the sugar profile variation under these conditions and identified a strong correlation between the best sugar profiles and cool temperatures during seed development. The impact of this work is the definition of the target sugar profile that can be obtained by producers under standard soybean production systems.

Technical Abstract: Soybean [Glycine max (L.) Merr] is an important crop because of the vegetable oil used for human consumption and the high protein meal used mainly for livestock feed formulations. For the highest quality soybean meal, the content of protein as well as the level of carbohydrates contributing positively or negatively to the potential metabolizable energy are considered. From a monogastric animal nutrition perspective, the positive carbohydrate present in soybean meal consists primarily of sucrose while the negative carbohydrate components are the raffinose family of oligosaccharides (RFOs) raffinose and stachyose. Therefore, increasing sucrose and decreasing raffinose and stachyose are critical targets to improve soybean functionality in feeds. Surveys of soybean germplasm have revealed relatively minor variation in the carbohydrate profile of seeds. However, recent advances in soybean molecular genetics have enabled the development and preliminary characterization of several modified carbohydrate profile soybean lines. In three of these modified carbohydrate lines, variant alleles of the soybean raffinose synthase 2 (RS2) gene are associated with increased sucrose and decreased raffinose and stachyose. The objective of this research was to compare the environmental stability of the seed carbohydrate profile of soybean lines containing either wild-type or variant alleles of RS2 utilizing a field location study and a date of planting study. The results demonstrated significant but not universal carbohydrate profile variation from environmental interactions. Strong correlations were identified between average maximum/minimum temperature during seed filling and carbohydrate content with some soybean lines responding more than others. The carbohydrate profile results are the first to define the environmental and genetic background-based variation in distinct regional and temporal environments using soybean lines with different alleles of the RS2 gene.