Genetic structure and mating system of wild cowpea populations in West Africa

Abstract

BackgroundCowpea is a highly inbred crop. It is part of a crop-weed complex, whose origin and dynamics is unknown, which is distributed across the African continent. This study examined outcrossing rates and genetic structures in 35 wild cowpea (Vigna unguiculata ssp. unguiculata var. spontanea) populations from West Africa, using 21 isozyme loci, 9 of them showing polymorphism.ResultsOutcrossing rates ranged from 1% to 9.5% (mean 3.4%), which classifies the wild cowpea breeding system as primarily selfing, though rare outcrossing events were detected in each population studied. Furthermore, the analyses of both the genetic structure of populations and the relationships between the wild and domesticated groups suggest possibilities of gene flow that are corroborated by field observations.ConclusionsAs expected in a predominantly inbred breeding system, wild cowpea shows high levels of genetic differentiation and low levels of genetic diversity within populations. Gene flow from domesticated to wild cowpea does occur, although the lack of strong genetic swamping and modified seed morphology in the wild populations suggest that these introgressions should be rare.

Grain Legumes

“…However, the source and sink trials cannot necessarily detect the shortest pollen movement. Source and sink trials typically examine pollen flow between spatially clustered groups of plants, usually separated by at least one meter (Kouam et al 2012). It has been demonstrated, more than 25 years ago, the utility of allozyme markers to estimate mating parameters, proportion of offspring produced by selfing, or its complement, the outcrossing rate (t = 1-s) (Barrett and Harder 1996).…”

Morphometric Analysis of some Species in the Genus Vigna (L.) Walp: Implication for Utilization for Genetic Improvement

“…The wild Vigna species such as V. vexillata, V. oblongifolia, V. luteola, V. racemosa and V. ambacensis which are found in many African countries could be exploited for food, medicine, agriculture (as cover crops and fodder) and more importantly for genetic improvement of cowpea (Kouam et al, 2012;Vijaykumar et al, 2012). The present study is aimed at evaluating the taxonomic affinities and genetic variabilities among 20 accessions of six Vigna species using morphometric analysis and to identify Vigna species that can serve as a bridge species between V. unguiculata and V. vexillata for inter-specific hybridization.…”

Assessment of the genetic diversity of cultivated common beans (Phaseolus vulgaris L.) from Cameroon and Kenya using allozymes markers

“…Since the species of concern is a tropical inbreed and bees pollinated legume (Koenig & Gepts, 1989), these results likely to fits with the general observation that inbreeding species maintain high and significant level of population differentiation (Hamrick & Godt 1990). Several other studies on other tropical inbreed crop species using allozyme concluded the presence of significant genetic differentiation: FST = 0.646 for wild cowpea (Kouam et al, 2012), FST = 0.712 in bambara groundnut and FST = 0.519 for wild lima bean (Bi et al, 2003). Gene flow is defined as the movement of gene within and among populations.…”

“…Conventionally, plant genetic diversity is estimated using variations in morphoagronomics traits such as yield, resistance, tolerance, colour and size (Szilagyi et al, 2011;Silva et al, 2016). Recently, biochemical markers such as allozymes (Kouam et al, 2012;Pasquet, 1999) and DNA based markers (Coulibaly et al, 2002;Semagn et al, 2006;Adesoye & Ojobo, 2012) have been more frequently used. Morphological and agronomics markers are highly influenced by the environment and generally shows low level of polymorphism compared to biochemical and molecular markers (Duminil & Michele, 2009) The aptitude to detect allelic variation at allozyme loci has modernized research in the field of evolution, biochemical and population genetics (Wendel & Weeden, 1989;Weir, 1996).…”