Assessing Intraspecific Variability and Diversity in African Yam Bean Landraces Using Agronomic Traits

Abstract

Landraces are repositories for potential beneficial traits which could be used to develop varieties with enhanced qualities. Optimal utilization of the available large collection of landraces of African yam bean (AYB) presently conserved at the Genetic Resource Center, International Institute of Tropical Agriculture, Ibadan (GRC-IITA), requires an assessment of the magnitude and nature of genetic diversity within the germplasm. One hundred and ninety-six AYB accessions were evaluated during the 2018 and 2019 cropping seasons in three agro-ecologies of Nigeria, using a 14 × 14 triple lattice design. The accessions were assessed for fourteen agronomic traits. Accession, environment, and accession × environment interaction effects were significant (p < 0.05) for all the traits. Variances due to environment and accession × environment interaction were higher than the genotypic variances. Similarly, estimates of phenotypic coefficient of variation (PCV) were higher than genotypic coefficient of variation (GCV) for all traits. Broad-sense heritability ranged from 17.1% (days to maturity) to 66.4% (seed length). Seed yield per plant had positive significant genotypic correlation with all the studied traits, except pod length and seed length. The first three principal components accounted for 59.7% of the total variation among the accessions and comprised of the 14 traits. Five major clusters were delineated based on phenotypic characteristics. Genetic variation was present among the AYB accessions, and these results will be useful for setting breeding goals and conservation approaches.

Characterization of African Yam Bean (Sphenostylis stenocarpa) Mutant Lines using Phenotypic Markers

“…The principal component (PC) showed that the first four PCs accounted for 75.54% of the total variation. A similar result was reported by Olomitutu et al (2022) who obtained 70.2% of the variation in the first four principal components in AYB lines. The relative discriminating power of the PCA determines character contribution to the total variation, and its discriminating power is dependent on the strength of the axis as measured by their eigenvalues (Idehen et al, 2016;Akinyosoye et al, 2017).…”

“…significant and positive correlation recorded between pair of seed yield and other agronomic characters suggests that these traits could be governed by similar genes with pleiotropic effect or closely linked genes (Brown and Caligari, 2008). The significant and positive correlation between yield-related traits suggested that the traits could be improved simultaneously (Olomitutu et al, 2022). Hence, any of these characters could be used in indirect selection to increase yield.…”

“…Phenotypic characterization also serves as a foundation for the selection of traits and the conservation of genetic resources. Thus, this method is cheap, reliable, and very easy to identify contributing or discriminating characters among breeding lines (Olomitutu et al, 2022). To validate the extent of genetic variability in germplasm, some scientists have used many statistical techniques, among which are principal components (PCA) and cluster analyses.…”

Genome-Wide Association Study Revealed SNP Alleles Associated with Seed Size Traits in African Yam Bean (Sphenostylis stenocarpa (Hochst ex. A. Rich.) Harms)

“…The germplasm consisted of 196 AYB accessions obtained from the existing collection of landraces at the Genetic Resource Center, International Institute of Tropical Agriculture, Ibadan, Nigeria. The passport data of the accessions can be found in Olomitutu et al [ 9 ].…”

“…The seed contains 22.5% protein, 53.7% carbohydrate, and 3.6% crude fat content [ 7 ]. Despite its numerous other benefits, low seed yield is one of the major constraints to its production [ 8 , 9 ] due to the absence of improved varieties and a lack of significant research attention.…”