Title : Genetic variability, heritability and genetic advance of yield and yield-related traits in soybean (Glycine max)
The success of breeding programme relies on the variability present in the breeding material. Selection is also effective when there is significant amount of genetic variability among the individuals in a population. The study aimed at assessing genetic variability among yield and yield components of soybean. Eighty-two genotypes maintained at the Agricultural Research Council-Grain Crops were planted in an alpha lattice replicated twice in Potchefstroom and Brits in South Africa in 2016/17 season. Five plants were selected and yield and yield related traits were measured. Data were analysed using analysis of variance, principal component and pairwise correlations. The means were separated using least significant differences. The genetic parameters were also estimated. The results showed highly significant differences among the genotypes based on days to flowering, branch number per plant, hundred seed weight, pod weight per plant, pod length, seed number per plant, seed number per pod and grain yield. Grain yield, seed number per pod, seed number per plant, pod length and number of pods per plant were highly significant and positively correlated with other traits. Days to flowering was negatively associated with pod length and seed number per pod, hundred seed weight was negatively correlated with days to flowering and number of branches. Heritability ranged from 5.9% to 100%. The most heritable traits were hundred seed weight, days to flowering and seed number per plant. The phenotypic variation ranged from 1.5% to 44%. The genotypic variance ranged from 0.3% to 33%. Most of the traits had medium variation whereas grain yield had the highest variation. The expected genetic advance was high for most of the traits, medium for seed number per pod and hundred seed weight and low for pod number per plant. The expected genetic advance as percent of mean was high for all traits. There was vast variation observed among the genotypes.