Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2008
Publication Date: March 17, 2009
Citation: Bellaloui, N., Smith, J.R., Ray, J.D., Gillen, A.M. 2009. Effect of Maturity on Seed Composition in the Early Soybean Production System as Measured on Near-isogenic Soybean Lines. Crop Science.49:608-620 Interpretive Summary: Soybean seed is a major source of protein and oil for human consumption and feed for livestock. Maintaining a high level of protein and oil in soybean seed is a major goal of the soybean industry. Previous research showed that seed protein and oil content significantly changed depending on cultivar, maturity of the cultivar and the environment under which they were grown. In previous studies the effect of cultivar and maturity could not be separated (confounded). To investigate the contribution of each of these variables to total protein and oil content separately, two sets of isolines were used. Isolines are soybean lines derived from a common ancestor, therefore they have the same genetic background, but each line differs from the other in one known gene, in this case genes for maturity). One set of isolines was derived from the cultivar Clark, and the other set from Harosoy. Results showed that protein percentage among Clark isolines increased as days to maturity increased. Oil percentage decreased as days to maturity increased among Harosoy and Clark isolines. Temperature had significant effect on seed composition; however, maturity or interactions effects between isoline set, maturity, and temperature explained a larger percentage of the variation in protein and oil content. Soybean breeders can use this information to develop new soybean varieties with higher seed protein and oil.
Technical Abstract: Seed composition varies significantly among soybean (Glycine max (L) Merr.) genotypes. The effect of maturity on seed composition is not well understood because maturity is generally confounded with genotypic background. The purpose of this study was to estimate the effect of maturity on seed composition using two sets of near isogenic soybean lines (Clark and Harosoy). The Clark isoline set had nine lines and the Harosoy isoline set had seven lines. The maturity of each line within a set varied, but all have a common genotypic background. There was a positive linear relationship between protein percentage and days to maturity among isolines of the Clark set in 2004 (r-square= 0.75; p less than 0.001) and 2005 (r-square= 0.63; p less than 0.001). However, in Harosoy isolines there was no relationship between protein and days to maturity. There was a negative linear relationship between maturity and oil percentage for Clark (in 2004, r-square = 0.82 and p less than 0.001; in 2005, r-square= 0.91 and p less than 0.0001) and Harosoy (in 2004, r-square = 0.19 and p less than 0.05; in 2005, r-square = 36 and p less than 0.01). Clark isolines showed a significant negative linear relationship between maturity and stearic acid in both years (in 2004, r-square =0.32 and p less than 0.01; in 2005, r-square=0.33 and p less than 0.01). A weak and significant (r-square = 0.28, p less than 0.001) linear relationship was found between the average maximum temperature 20 days before maturity and protein and oil in Clark isolines in both years. Both maturity and temperature had significant effects on seed composition. However, maturity had greater effects on seed composition and contributed more to total seed composition variation than temperature. Genotypic background of Clark isolines had a different relationship between days to maturity and seed composition than Harosoy isolines. This information will be useful for soybean breeding in developing new germplasm for seed composition.