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

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.