Development of breeder-friendly KASP markers for low concentration of kunitz trypsin inhibitor in soybean seeds

Authors: ROSSO, LUCIANA - Virginia Tech; SHANG, CHAO - Virginia Tech; ESCAMILLA, DIANA - Purdue University; GILLENWATER, JAY - North Carolina State University; Song, Qijian; ZHANG, BO - Virginia Tech

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2021
Publication Date: 3/6/2021
Citation: Rosso, L., Shang, C., Escamilla, D.M., Gillenwater, J., Song, Q., Zhang, B. 2021. Development of breeder-friendly KASP markers for low concentration of kunitz trypsin inhibitor in soybean seeds. International Journal of Molecular Sciences. 22:2675. https://doi.org/10.3390/ijms22052675.
DOI: https://doi.org/10.3390/ijms22052675

Interpretive Summary: Although soybean is widely recognized as the best and least expensive source of vegetable protein for livestock, poultry and aquaculture production, soybean seeds have several anti-nutritional factors (ANFs) including Kunitz trypsin inhibitor(KTI) that affect animal nutrient digestion and absorption and reduce animal meat growth performance. The meal industry roasts raw soybean meal to inactive ANFs, but heating can degrade certain essential amino acids and increase energy costs. Thus, the industry has great demands for soybeans with low KTI, but so far, such commercial varieties have not been made available partially due to the lack of an efficient approach to screen for low KTI lines in breeding programs. In this study, we identified a DNA linked to low KTI activity from soybean accession PI 547656 and developed a robust, cost-effective and high-throughput DNA marker assay to identify lines with low KTI. Validation using a set of 93 diverse germplasm types showed that the assay had 86% accuracy for the prediction of low KTI soybeans. The DNA assay is expected to facilitate selection for low KTI content in soybean seeds across different genetic backgrounds and environments in soybean breeding programs and significantly accelerate low KTI breeding. These findings will be important to scientists working to improve the nutritional content of soybeans.

Technical Abstract: Soybean has several anti-nutritional factors such as trypsin inhibitors (TI), which inhabit animal protein digestibility and lower animal growth performance. The trypsin inhibitors are usually inactivated by roasting raw soybean meal, but this practice reduce the amino acid bioactivity and increase processing cost. Currently, no commercial soybean cultivars with low or null concentration of trypsin inhibitors is available. Thus, the objective of this study was to identify quantitative trait loci (QTLs) controlling low TI, particularly Kunitz trypsin inhibitor (KTI) in soybean seeds in order to facilitate low TI soybean breeding. A total of 200 F4 lines derived from PI 547656 (low KTI) X Glenn (normal KTI) were genotyped using the BARCSoySNP6K_v2 Beadchip. F3, F4 and F5 lines from the population were grown in Blacksburg and Orange, Virginia in two years, respectively, and were measured for KTI content using quantitative HPLC method. We identified a major QTL on chromosome 8 which explained 41.94 % of the phenotypic variation for low concentration of KTI. Of the three SNP markers significantly associated with low KTI and validated in a set of 93 diverse germplasm accessions, the marker BARC_1.01_Gm08_44814503 has approximately 86% selection accuracy for the accessions with low TI.