| Soyfood cultivars have high quality requirements and inferior yield compared to commodity soybean [Glycine max (L.) Merr.] The study objectives were to: (1) examine irrigation, row spacing, and planting date effects on agronomics and quality of food-grade soybean; (2) determine heritabilities and interrelationships among agronomic and seed quality traits; and (3) develop an objective seed texture test. Food-grade genotypes were evaluated in six environments for hardness, protein, oil, sucrose, raffinose, stachyose, and calcium content; and agronomic traits of yield, seed size, height and maturity. The experiment was arranged in a strip-strip-strip-plot design with three replications and analyzed by SAS and Agrobase. Sugar content was quantified with HPLC, protein and oil was determined by NIR. Steamed seed hardness was determined by texture analyzer equipped with a shear cell, blade, probe, cylinder, or pea rig. Calcium content was determined by ICP using the HNO3 method. Irrigation increased yield, height, and seed size (21%, 9%, and 5%, respectively) but did not significantly impact quality. The May planting produced taller plants and higher yields than April and June (31% and 11%, respectively) but did not impact seed quality. Row spacing did not significantly impact any trait; G x E effect was significant for all traits. Seed size, calcium, and stachyose contents were highly heritable (h2 = 0.89, 0.82, 0.78; respectively) and the strongest correlations were yield and height (r = 0.62) and protein and oil (r = -0.51). The blade and cylinder were the most precise hardness tests; seed size and swell ratio by weight could be used for indirect selection. Altering cultivation practices can increase yield, but may not improve quality. Breeders may utilize these heritabilities and interrelationships in breeding schemes to maximize yield and quality. |
