Improving soybean seed quality

Both the meal and oil fractions of soybeans may be genetically improved, either by mutagenesis or by genetic engineering. There are a number of mutant lines of soybeans containing a low raffinosaccharide meal, which can be used for animal feed, with an improved total metabolizable energy content. Mutant lines with an improved fatty acid profile of the oil include high oleic and high stearic soybeans. Cloning of the mutant genes facilitates the integration of these traits into high yielding elite lines by providing molecular markers. Cloned genes may also be reintroduced into soybeans to create transgenic lines with improved meal and oil traits, such as seeds with an increased lysine content and stable soybean oils with a very low content of polyunsaturated fatty acids. The design of transgene constructs has been assisted by using soybean somatic embryos in suspension culture as a model system for soybean seed transformation. This system has allowed selection of those genes and promoters that are the most effective way of achieving the desired phenotypes in soybeans. Experiments with constructs containing fatty acid biosynthesis genes in somatic embryos have also led to the conclusion that, in soybeans, gene-transgene sense suppression is a more effective way of silencing endogenous genes than antisense. Sense suppression of genes encoding microsomal, fatty acid omega-6 desaturates has resulted in soybean lines with over 80% oleic acid in their seed oil, and this trait is stable over at least three generations. (author). 12 refs, 2 figs