Morphological diversity analysis of African yam bean (Sphenostylis stenocarpa Hochst. ex A. Rich.) Harms and prospects for utilization in germplasm conservation and breeding

Abstract

African yam bean (AYB, Sphenostylis stenocarpa Hochst. ex A. Rich.) Harms is a tuber and seed crop, rich in protein, with the potential to contribute to food security. To date, available information on the diversity of AYB is scarce. This study aims at understanding the genetic diversity of 79 AYB accessions of various origins. Twenty-four morphological and taxonomic features of high descriptive values were used and the diversity within the germplasm was assessed by clustering analysis. The 79 accessions differed significantly, with the similarity distances spanning from 0.0646 to 0.5720 and a mean distance of 0.2820. The accessions were grouped into five clusters of 10-26 members. Of the 24 phenotypic variables analyzed, variegation in testa color was the most discriminatory trait, classifying the accessions in the proportion of 25% with variegated to 75% with non-variegated seeds. The ranking by significance (P B 0.05) of the ordinal variables of discriminating importance were in the order of pattern of testa variegation, basal color of variegated seeds, and testa basal color. The stepwise discriminant and frequency procedures in SAS identified other phenotypic variables with significant discriminatory attributes, such as pigmentation of plant parts, seed cavity ridges, and pod dehiscence. Accessions with desirable agronomic traits, such as longer pod length, high number of seeds/pod, non-shattering characteristics of pods at maturity, lower number of days to flowering, and a higher seed set percentage, were also identified in this study. These discriminatory traits are discussed and proposed for germplasm conservation and use.

A Review on Genetic Resources, Diversity and Agronomy of African Yam Bean (Sphenostylis stenocarpa (Hochst. Ex A. Rich.) Harms): A Potential Future Food Crop

“…Each pod can yield up to twenty seeds which may be rounded, oval, oblong or truncated (Milne-Redhead and Polhill, 1971;Adewale et al, 2012). The mat or shiny seeds can be mono-colored or mosaic.…”

“…Presently in Ghana and Nigeria, there is a dwindling interest in the production of AYB among the farmers (Amoatey et al, 2000;Olisa et al, 2010). Only a very small sector of the farmers appreciates its cultivation, hence, they are the holder of the crop ' s genetic resources (Adewale et al, 2012).…”

“…The tuber shapes of AYB as observed by Adewale (2011) and Adewale and Dumet (2011) varied and included round, oval, spindle and irregular. Results from phenotypic evaluation of small (≤ ten) to large (≥ 30) number of accessions of AYB revealed wide intra-specific variability for some agro-morphological variables (Potter, 1992;Ene-Obong & Okoye, 1992;Akande, 2009;Adewale et al, 2010, Popoola et al, 2011aAdewale et al, 2012).…”

Fruit and seed biometry of cambuí (Myciaria tenella O. Berg)

“…Moreover, it is necessary to characterize and conserve natural resources to prevent the species extinction. The characterization of genotypes is an essential step in breeding programs and conservation of germplasm (ZUBRZYCKI, 1997;SMIDERLE;ADEWALE et al, 2012). The characterization provides important insights regarding the handling and packaging, commercial exploitation, and agriculture industry, contributing to the proper use and application of technological methods (OLIVEIRA et al, 2009).…”

Floral Maturation Indices of African Yam Bean (Sphenostylis stenocarpa Hochst Ex. A. Rich) Harms (Fabaceae)

“…The present experiment was carried out on ten selected accessions from the 79 accessions of African yam bean collected from the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria, whose morphological diversity was earlier reported by Adewale et al (2012). Each was planted in a row of ten plants in three blocks at spacing of 1 m x 1 m in a field at IITA, Ibadan (7.5 °N, 3.9 °E).…”