Phenotypic and Marker-Assisted Selection for Soybean Genotypes with Food-Grade Seed Traits.

Changes in mainstream trends towards healthier diet have helped uncover the nutritional value and health benefits of soybean. Soyfood revenues have been steadily increasing in the USA at a rate of 10 to 25% per year, and recent reports forecast that soyfood sales will reach $55 billion by 2015. Development of food-grade cultivars is, therefore, imperative for soybean breeders. The objectives of this research were to 1) identify genotypes with high protein, high sucrose, and large seed size for edamame and tofu, 2) identify molecular markers linked to seed protein and sucrose QTL. A population of recombinant inbred lines (RIL) derived from the cross between a high protein line (R95-1705) and a large seeded cultivar with moderately high sucrose were evaluated at two Arkansas locations during 2007 and 2008. Seed size, protein, sucrose, raffinose and stachyose content were measured in a seed sample from each plot after harvest. Results showed a continuous distribution for all the traits measured, suggesting a quantitative inheritance of the traits. Mean and standard deviation of the RIL population were similar across environments for all the traits except for raffinose and seed size. Averaged data over years and locations showed that four lines exhibited seed size larger than 20 g/100 seeds with protein content higher than 45% and an average seed sucrose content of 3.7%. Large seeded lines (> 20 g/100 seeds) showed an average sucrose content of 4.01%. Two SSR markers (Satt614 and Satt496) on linkage group I were significantly associated with seed protein and sucrose but with opposite effects, which may contribute to the negative correlation between these two traits. These lines could be used in future breeding efforts to incorporate the large seed size with high protein or sucrose traits into adapted high yield cultivars. The molecular markers reported here could be used in marker assisted breeding for high protein and sucrose.