Genotype by Environment Interaction and Stability Analysis for Carbon Isotope Discrimination, Ureide Concentration and Nitrogen Fixation in Soybean.

Carbon isotope discrimination (D¹³C), ureide concentration and nitrogen fixation (N-fixation) have been suggested as criteria for indirect selection for water use efficiency and yield improvement in soybean.  A large number of accessions from the USDA-ARS Soybean Germplasm Collection were examined for these traits at two locations in 2009 and 2010. The objectives of this study were to determine the magnitude of genotype by environement (GxE) interactions and stability among these genotypes and to identify genotypes with stable performance for one or combinations of these traits. Significant (P ≥ 0.001) environment, genotype and GxE interactions effects were observed for (D¹³C) and ureide. The N-fixation did not show a significant (P ≤ 0.05) GxE interaction, but, the environment and genotype effects were significant (P ≥ 0.001). Trait based identification of the genotypes was carried out using stability index, mean squared deviation (MSD) from regression analysis and genotype ranking. The performances of several genotypes were consistent across environments and between the studied traits. A total of 60 genotypes were identified for a trait of interest or a combination of traits based on their stability index, lower MSD and their ranking. Many of these genotypes represented stability in two are more traits simultaneously. The identified genotypes may be used for further evaluation of growth and physiological characteristics and in trait-based breeding programs to develop new cultivars with higher water use efficiency and improved yield.