High-protein soybean lines with stable seed protein content under heat and drought stresses

A significant factor determining the value of soybean is protein content, in addition to its importance as an oilseed. Increasing the seed protein content in soybean will make it a more valuable food and feedstock and enhance its importance in the international market. Due to this reason, developing high-protein soybean varieties is gaining increased industrial interest. To ensure profitable production, the stability of the high-protein trait needs to be verified under environmental stresses. The objectives of this study were to test whether the highprotein soybean genotypes can maintain their high seed protein content under heat and drought stresses imposed during seed filling and to assess the changes in their oil composition under stress conditions. The changes in seed protein and oil contents and oil composition of the high-protein lines NLM09-77, N14-7017, and N16-9924 under heat and drought stresses were assessed and compared against those of a recently released highyielding, high-protein variety Benning HP; elite cultivars NC-Dunphy, NC-Raleigh, and NC-Dilday; low-protein breeding lines N11-9228 and N09-2505; heat-tolerant line DS25-1; and heat-susceptible line DT97-4290. We found that the high-protein genotypes NLM09-77, N16-9924, N14-7017, and Benning HP maintained their high seed protein contents under heat and drought stresses (46-55 %). Among them, NLM09-77 and N14-7017 were unique with no apparent negative relationship between the seed protein and oil contents. In terms of oil composition, N14-7017, NLM09-77, and Benning HP were similar to the elite cultivars NC-Dunphy and NCDilday. Additionally, the high-protein genotypes N14-7017, NLM09-77, and Benning HP did not exhibit any yield drag (2993-3150 kg ha(-1) vs 3289-3368 kg ha(-1) for the elite cultivars). Taken together, our study demonstrates the usefulness of the advanced breeding lines NLM09-77 and N14-7017 and cultivar Benning HP for developing new varieties with enhanced nutritional value under climate change-associated stresses.