Effect of Maturity on Seed Composition in the Early Soybean Production System as Measured on Near-Isogenic Soybean Lines

The effect of maturity (time to maturity) on seed composition in soybean [Glycine max (L.) Merr.] genotypes is not well understood because maturity is generally confounded with genotypic background. Therefore, the effects of maturity on seed composition were estimated in two sets of near isogenic soybean lines ('Clark' and 'Harosoy'), where the maturity of each line within a set varied, but all had a common genotypic background. There was a positive linear relationship between protein concentration and maturity among isolines of the Clark set in 2004 (r(2) = 0.75; P <= 0.001) and 2005 (r(2) = 0.63; P <= 0.001). However, in Harosoy isolines there was no relationship between protein and maturity. There was a negative linear relationship between oil concentration and maturity for Clark (in 2004, r(2) = 0.82, P <= 0.001; in 2005, r(2) = 0.91, P <= 0.0001) and Harosoy (in 2004, r(2) = 0.19, P <= 0.05; in 2005, r(2) = 0.36, P <= 0.01). Maturity had greater effects on seed composition than maximum temperature. The results indicate that the relationship between seed composition and maturity was different between the Clark and Harosoy sets of isolines. However, the overall mean of protein and oil concentration was not different between genotypic backgrounds. This information will be useful for soybean breeding in developing new germplasm for seed composition.