Stability and genotype by environment analysis for quality, yield and yield components of soybean [Glycine max (l.)] lines

Abstract

Soybean [Glycine max (L.) Merrill.] Breeders’ prefer genotypes with high grain yield along with high oil and protein content. Soybean in Kenya is important in the manufacture of feed, food and natural resource management. Availability of high yielding and stable varieties is among the constraints that limit adoption and production of soybean in Kenya. The objectives of the study were to determine the performance of fifteen soybean genotypes in five environments, the broad sense heritability for yield and its components as well as determine stable genotypes for yield, oil and protein content. A randomized complete block design was used for the study. Combined analysis of variance was done to get the performance of the genotypes. Broad sense heritability was estimated by variance component method. Additive main effects and multiplicative interactions (AMMI) then genotype and genotype plus environment (GGE) bi-plots were used to determine stable genotypes. The analysis of variance indicated environments, genotypes and genotype by environment interactions to be highly significant (P < 0.01) for traits studied. The mean seed yield was 1267.8 kg ha-1. Genotype Nyala gave the highest seed yield of 1600.9 kg ha-1 while DPSB 3 (TGX 1835-10E) gave the lowest yield of 661.7 kg ha-1. The mean oil content ranged from 166.0 g kg-1 - 219.0 g kg-1 for genotypes DPSB 19 and 931/5/34, respectively. The mean protein content ranged from 352.0 g kg-1 for genotype 931/5/34 to 403.0 g kg-1 for genotype DPSB 19 (TGX 1740-2F). Broad sense heritability was low for protein and oil content, pods per plant, number of branches, seed yield, and high for 50% flowering, plant height, number of seeds per pod and number of nodes per plant. Seed yield was positively correlated to oil content and negatively correlated to protein content while plant height was positively correlated to nodes per plant. Genotypes EAI 3600 and SBH 4/6/6 had stable yields above the mean while genotypes SBH 4/4/4, SBH 7/1/1, 1/12/9 and Gazelle were stable in yield and oil content. Because these genotypes are high in seed yield and oil content, they could be directly grown by farmers in the test environments or used in breeding programmes to develop new varieties. Key words: Soybean, genotype by environment, stability, heritability.