GENETIC VARIABILITY AND SELECTION INDICES FOR YIELD AND NUTRITIONAL QUALITY OF SOYBEAN (Glycine max L. Merrill) IN THE SOUTHERN GUINEA SAVANNA OF NIGERIA

Genetic improvement of soybean (Glycine max L. Merrill) is essential for enhancing yield and nutritional security in sub-Saharan Africa. This study evaluated the genetic variability, heritability, and genetic advance of sixteen soybean genotypes at the National Cereals Research Institute, Badeggi, Nigeria, across the 2019 and 2020 rainy seasons. Observations were recorded on various yield and yield-contributing characters, namely: days to 50% flowering, days to maturity, plant height, first pod height, stand count per plot, number of branches per plant, number of pods per plant, 100-seed weight, fodder weight per plot, and grain yield per plot at the field level. Additionally, moisture, ash, oil content, protein content, crude fibre, and total carbohydrate content were evaluated in the laboratory. Analysis of variance (ANOVA) revealed highly significant variability for all the studied characters. High values of genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were observed for characters such as fodder weight (31.86/32.06), yield per plot (25.16/25.38), number of pods per plant (23.23/27.31), crude fibre (21.75/25.07), and ash content (21.18/24.55), indicating the presence of high genetic variation. High broad-sense heritability (h2) coupled with high genetic advance as percentage of means (GAM) was observed for traits including fodder weight (h2 = 99%; GAM = 65.2), and grain yield (h2 = 98%; GAM = 51.4). Furthermore, ash (74%/37.6) and crude fibre (75%/38.9) exhibited high estimates, suggesting that these traits are governed by additive gene action and can be improved through direct selection. These results suggest that genotypes with high yield and superior nutritional profiles can be effectively utilized in future soybean improvement programs in the Southern Guinea.