Soybean is an important food and cash crop in Uganda. Despite the importance of soybean in Uganda’s economy, its performance is highly affected by genotype × environment interaction making it difficult to select and recommend new superior soybean genotypes for diverse growing environments. The objectives of this study were to examine the nature of G × E interaction for soybean grain yield, to identify stable and high yielding soybean genotypes with desirable percentage protein and oil content for production in diverse environments and to determine ideal test location for future soybean breeding activities in Uganda. The experiment was conducted at six locations for two consecutive seasons of year 2018 (2018A and 2018B). Twenty-three newly advanced generation soybean lines and two commercial varieties were evaluated in a randomized complete block design replicated three times. Combined analysis of variance over locations and seasons was carried out for grain yield, protein and oil (%) content. The results for grain yield showed significant (p<0.05) differences for all the sources of variation except genotypes × season interaction. Percentage protein and oil content showed non-significant (p>0.05) for all the sources of variation except location. The genotype main effect plus G × E interaction biplot explained 65.74% of the total interaction sum of squares for grain yield and showed that the advanced generation soybean lines BSPS 48A-28; Mak 3N × 1N and NGDT 8.11×3N-2 were high yielding and stable and had other desirable agronomic traits. Nakabango was the most discriminating and representative test location.
Key words: Soybean, stability, GGE, ideal testing location, mega-environment.
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