Interaction of Genotype x Sowing Date on Yield and Associated Traits of Soybean [Glycine max (L.) Merrill] over Two Cropping Seasons in a Humid Agro-ecological Zone of South-Eastern Nigeria

Abstract

The study evaluated four soybean genotypes in 2012 and 2013 cropping seasons in the humid tropics for growth, seed yield and other reproductive characters. A split plot in randomised complete block design with four replications was used at National Cereals Research Institute, Amakanma sub-station, Abia State, Nigeria (latitude 05º 28´ N, longitude 07º 29´ E ,154.25 m asl). Sowing date was the main plot treatment while soybean genotypes were fitted into the subplots. Sowing date significantly affected soybean yield and yield components with the month of July pointing out as most appropriate sowing time for the crop in the humid tropics of southeast Nigeria. TGx1485-1D soybean genotype consistently exhibited high performance in seed yield and in most of the characters studied across both environments while TGx1987-10F had the least, hence can be tipped as good breeding material for development of high yielding soybean varieties that would have high adaptation to the agro-ecology. Correlation and path analysis revealed that number of pods plant-1 among other traits was the most important contributor to seed yield and demands close attention as selection index for crop improvement. TGx1485-1D though high yielding exhibited low yield stability across both environments in the GGE bi-plot ranking where it ranked closest to the ideal genotype, hence, can be recommended as suitable for cultivation in the humid tropics of southeast Nigeria. Also, the genotype could be exploited for future breeding programs aimed at boosting research in developing high yielding, adaptable, disease resistance and stable genotypes for the region.