Agronomic and Phenological Differences of Soybean Isolines Differing in Maturity and Growth Habit

The effects of maturity genes (E genes) on flowering, maturity, and the seed filling period of soybean [Glycine max (L.) Merr.] have previously been described. However, little work has been done to quantify the effect of maturity and growth habit genes on morphological and phenotypic traits. This study quantifies the effects of maturity and growth habit genes on morphological and phenotypic traits to understand better how these genes may be most agronomically beneficial in northern short‐season breeding programs. Four near‐isogenic pairs consisting of e1e3e4, e1e3E4, e1E3E4, and E1e3e4 maturity gene combinations containing either indeterminate (Dt1) or determinate (dt1) stem termination type were grown near Woodstock, ON, in 1994 and 1995. When averaged across growth habit, the presence of an additional dominant maturity gene significantly increased the time to the start of the seed filling period (SSFP) and days to maturity. Lines with dominant E genes exhibited increased height, final node number, and lodging, and decreased harvest index. Indeterminate growth habit caused increased days to SSFP in 1995, and increased days to maturity, height, and lodging and decreased harvest index in both years. A positive relationship between whole‐plant seed filling rate (SFR) and yield occurred in the Dt1 lines in both years and occurred in the dt1 lines in 1994. There was a positive relationship between whole‐plant seed filling period (SFP) and yield in the dt1 lines in 1995. The E1dt1 line consistently had the highest seed filling rate of any isoline. The data indicated that the E1dt1 combination may have unrealized potential in short‐season breeding programs.