GENETIC VARIABILITY STUDIES OF SOME NIGERIAN SOYBEAN (GLYCINE MAX (L) MERRIL) ACCESSIONS

Abstract

Soybean is a very important leguminous seed crop; known for its highly valued protein and oil owing to its use in food, feed and industrial applications. The cultivation of soybean could be of great impact in curbing food insecurity and its improvement could be of great benefit to humanity. Genetic variability is the basic requirement for crop improvement as it provides wider scope for selection. Selection of traits through morphological and molecular means increases the frequency for favourable alleles which can be explored in breeding programme for any crop. Therefore, study on genetic variability among soybean was undertaken to evaluate the genetic variation among some accessions of soybean for effective selection, utilization and improvement. Twenty accessions of soybeans were collected from the gene bank of International Institute of Tropical Agriculture (IITA), Ibadan. The accessions were evaluated for agro- morphological parameters using randomized complete block design (RCBD) with three replicate. Soybean accessions were further evaluated for genetic diversity using simple sequence repeat (SSR) marker, pollen parameters was also used to characterize the accessions. There are significant (P < 0.05) wide ranges of variability observed in all the morphological characters assessed, with specific accessions being favoured by different trait(s). Accessions TGX–2016-4E recorded the highest plant height (46.17cm), TGX–1485-1D recorded highest pod production (216.47) and TGX-2027-1E recorded the highest seed yield per plant (1167.67). Wide variability was also observed for qualitative traits such as leaflet size, leaflet shape, pubescence, pubescence density, pubescence colour, pubescence type, cotyledon colour, corolla colour, seed shattering and mature pod colour. The phenotypic coefficient of variation was higher than the genotypic coefficient of variation for all the traits. Moderate to high broad sense heritability ranging from 32.99 to 95.37 was obtained and the genetic advance as percentage mean ranges from 0.16%-58.89%. Most of the accessions exhibit high pollen viability up to 84.60%; except TGX-2010-11F which had 26.70%. Molecular diversity of 11 selected genotypes from the initial twenty accessions using simple sequence repeat (SSR) DNA marker generated 150-320 base pair with six primers. Genetic similarity among the genotypes varies from 0.17-4.09 with an average gene diversity of 0.28. Clustered dendrogram of the 11 genotypes revealed two major clade (TGX- 1987-62F and TGX-2011-6F). The high genetic variability obtained for both morphological and molecular characterizations coupled with high heritability and genetic advance in most parameters studied indicate that the genotypes could be selected for those heritable traits and used as tool for crop improvement.