Abstract

Eight soybean varieties were evaluated in 2006 and 2007 at three locations in the forest and savanna agro-ecologies of South west Nigeria for grain yield and other reproductive characters. Data were analyzed using analysis of variance and genotype plus genotype x environment interaction (GGE) biplot analysis. The main effects of year, location, variety and their interactions had significant effects on all the characters except pod length and number of seeds per pod. Among the varieties, number of days to 50% flowering, number of seeds per pod and 100 seed weight had average values of 45.29, 2.31 and 13.07 respectively while that of   grain yield was 1027.49 kg/ha. The highest yielding variety across years and locations was TGx 1805-31F while TGx 1485-1D had the lowest value. Grain yields recorded in 2006 and 2007 were 1059.94 and 995.04 kg/ha. Ballah (southern guinea savanna) produced the highest grain yield while Ilora (derived savanna) had the least. GGE biplot analysis showed that genotype, location and genotype x location interaction were responsible for 21.66, 37.63 and 40.71% of their total variations respectively. The variety TGx 1922-1F was found to be high yielding and stable. Suitable varieties were also identified for the three locations under evaluation.

Key words: Soybean, genotype, environment, grain yield, adaptation.