Relationships Between Soybean Seed Sugars as Affected by Maturity in near-Isogenic Soybean (Glycine max ) Lines.

Genotypic background and maturity have been confounded in previous studies of soybean seed composition. The objective of this study was to investigate the relationship between seed sugars (sucrose, raffinose, and stachyose) and both maturity and field air temperature in two sets of near-isogenic lines of Clark and Harosoy. The maturity of each line within each set varied, but all lines from each set shared a common genotypic background. The results showed that in the Clark isoline set, maturity had a negative linear relationship with the concentration of sucrose (r²=0.83 in 2004; r²=0.94 in 2005), stachyose (r²=0.51 in 2004; r²=0.51 in 2005), and combined sugars (sucrose+raffinose+stachyose) (r²=0.83 in 2004; r²=0.91 in 2005). In the Harosoy set, there were significant negative relationships between maturity and sugars only in 2005 for sucrose, stachyose, and combined sugars. In the Clark set, temperature had a significant positive relationship with sugars in 2004, but significant negative relationship in 2005. In the Harosoy set, there was a significant negative relationship between air field temperature and sugars only in 2005.  It was concluded that the effect of genotypic background and maturity genes on sugar concentration depended on the type of sugar. This study highlights the impact of maturity and temperature on seed sugars and provides soybean plant breeders with information on the necessity of considering these effects in their breeding program as related to their target production region such as the Early Soybean Production System.