Enhancing Seed Quality and Application of Soybean through High Test Weigh and Low Trypsin Inhibitors

Soybean is an integral oilseed crop that is used all over the world. Despite this, soybean has been experiencing a decrease in seed quality seen by the decreasing trend in test weight, and is limited in its uses due to the antinutritional factor, trypsin inhibitor (TI). This project first worked to identify single nucleotide polymorphisms (SNPs) associated with high test weight through a genome-wide association study (GWAS) as well as determine the relationship between important seed composition traits and test weight. Additionally, it focused on identifying and knocking out KTI genes specifically expressed in soybean seed tissue through CRISPR/Cas9. Lastly, this project investigated further use of soybean in aquaculture by evaluating the performance of Rainbow trout fed diets with low-TI, 'VT Barrack' soy meal. Nine SNPs on chromosome 15 were found to be significantly associated with high test weight as and eight potential gene candidates were identified. Test weight was found to be significantly, and negatively related to seed oil content and had inconsistent correlations with protein and sugar content. The KTI genes KTI1, Glyma01g095000, and KTI3, Glyma08g341500, were found to be only expressed in seed tissues and multiple KTI knock-out soybean plants with decreased seed TI content and activity were developed. Lastly, we found that our low-TI soymeal could replace 30% of fish meal in aquafeeds with no negative effects on trout growth and health.