Genetic Improvement of U.S. Soybean in Maturity Groups V, VI, and VII
J. D. Boehm Jr., H. Abdel-Haleem, W. T. Schapaugh Jr., K. Rainey, V. R. Pantalone, G. Shannon, J. Klein, T. E. Carter Jr., A. J. Cardinal, E. R. Shipe, A. M. Gillen, J. R. Smith, P. Chen, D. B. Weaver, H. R. Boerma, and Z. Li.  2019.  Crop Science, 59:1838-1852.

Soybean is an important source of protein and vegetable oil. Genetic improvement of soybean yield and seed composition is an ultimate breeding goal. Over the past 80 years, breeders have worked diligently to select for high yield and other desired traits over time to make genetic improvements. The objectives of the present study were to evaluate 93 soybean cultivars selected from Maturity Groups (MG) V, VI, and VII that were released by breeders from 1928 2008 for genetic changes to seed yield, yield stability, and other important agronomic and end-use quality traits that may have occurred over an 80 yr period due to breeder selection. In 2010-2011, replicated yield trials specific for each MG of cultivars were conducted in a total of 27 southeastern U.S. environments. A mixed linear model was used to calculate best linear unbiased predictors (BLUPs) for each cultivar for each measured trait within each MG. Regressed BLUP trait values by year of cultivar release revealed positive linear trends for annualized genetic yield gains of 17.6, 13.5, and 10.3 kg ha-1 yr-1 for MG V, VI, and VII, respectively. Across the MGs, the annualized rate of genetic gain was estimated to be 13.7 kg ha-1 yr-1. Yield stability analyses revealed that regression coefficients (b) for newer cultivars were greater than 1.0 and much higher than older cultivars, confirming that yield stability changes occurred over time. Overall, the data indicates that a yield plateau has not been reached for MG V, VI or VII soybean cultivars.