Genetic structure and mating system of wild cowpea populations in West Africa
1 International Centre of Insect Physiology and Ecology, P.O box 30772, Nairobi, Kenya
2 Department of Agriculture, Faculty of Agronomy and Agricultural Sciences, University of Dschang, PO Box 222, Dschang, Cameroon
3 IRD, Institut de Recherche pour le Développement, UR 072, Laboratoire Evolution, Génomes et Spéciation, UPR 9034, Centre National de la Recherche Scientifique (CNRS), 91198, Gif sur Yvette Cedex, France
4 Université Paris-Sud 11, 91405, Orsay Cedex, France
5 CREAF de Kamboinse, INERA, BP 476, Ouagadougou 01, Burkina Faso
6 Faculté des Sciences, Département de Biologie, BP 243, Niamey, Niger
7 UMR System 2, place Viala, 34060, Montpellier, France
8 CSIR-SARI, PO Box 52, Tamale, Ghana
9 Department of Biochemistry and Biotechnology, Kenyatta University, P.O Box 43844, Nairobi, Kenya
10 Department of Plant Sciences/MS1, Section of Crop and Ecosystem Sciences, University of California, 1 Shields Avenue, Davis, CA, 95616-8780, USA
BMC Plant Biology 2012, 12:113 doi:10.1186/1471-2229-12-113Published: 24 July 2012
Cowpea 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.
Outcrossing 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.
As 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.