Evaluation of Several Agronomic Traits in ‘Essex’ By ‘Forrest’ Recombinant Inbred Line Population of Soybean [Glycine max (L.) Merr.]

Crop yield is a polygenic complex trait and its improvement is a major goal of breeding programs. The objective of this study was to compare yield and its components along over a period of four years (2007-2010) in three locations in North Carolina using the ‘Essex’ by ‘Forrest’ recombinant inbred line (RIL) population of soybean (ExF, n=94). The RILs distribution for all traits showed higher means than their respective mid-parental values but do not differ significantly at P<0.05. Nearly 45% of the lines germinated later than 6 days which is the mean for the slower germinating parent, Essex. In approximately 63%, the first flower appeared at 52.5 days, which is the mean mid-parental value. As for seed weight, RILs showed better performance than parental lines and 46% of the plants exceeded the higher yielding parent, Forrest. Seed weight showed the highest level of variation ranging from 54.1% for year to 70.7% for genotype. The lowest coefficients of variation (CVs) on average were calculated for flowering time and did not exceed 31.6%. In contrast , the year of the experiment caused the lowest level of variation for the traits studied while the genotype caused the highest level of variation. Seed germination was positively correlated with plant height (r=0.441 at P<0.001) and negatively correlated with both flowering time (r=-0.374 at P<0.001) and seed weight (r=-0.357 at P<0.001) across environments. Flowering time was found negatively correlated with plant height (r=-0.579 at P<0.001) and positively correlated with seed weight. The ExF population performed well in all environments compared to other populations tested in the same environments. The results presented here can be beneficial to NC soybean breeding programs that aim to create superior high yielding and disease free cultivars adapted to several NC environments.