Abstract
We present the first study of patterns of genetic diversity of sorghum landraces at the local scale. Understanding landrace diversity aids in deciphering evolutionary forces under domestication, and has applications in the conservation of genetic resources and their use in breeding programs. Duupa farmers in a village in Northern Cameroon distinguished 59 named sorghum taxa, representing 46 landraces. In each field, seeds are sown as a mixture of landraces (mean of 12 landraces per field), giving the potential for extensive gene flow. What level of genetic diversity underlies the great morphological diversity observed among landraces? Given the potential for gene flow, how well defined genetically is each landrace? To answer these questions, we recorded spatial patterns of planting and farmersâ perceptions of landraces, and characterized 21 landraces using SSR markers. Analysis using distance and clustering methods grouped the 21 landraces studied into four clusters. These clusters correspond to functionally and ecologically distinct groups of landraces. Within-landrace genetic variation accounted for 30% of total variation. The average F is over landraces was 0.68, suggesting high inbreeding within landraces. Differentiation among landraces was substantial and significant (F st = 0.36). Historical factors, variation in breeding systems, and farmersâ practices all affected patterns of genetic variation. Farmersâ practices are key to the maintenance, despite gene flow, of landraces with different combinations of agronomically and ecologically pertinent traits. They must be taken into account in strategies of conservation and use of genetic resources.
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Acknowledgments
This work is part of the PhD thesis of the first author. This research was funded by a grant from the âInstitut Français de la BiodiversitĂ©â. We thank Claire Billot and the Montpellier Languedoc-Roussillon Genopole platform for technical assistance. We acknowledge the help of J. Chantereau of CIRAD in the racial characterization of landraces. We thank the government of Cameroon for allowing us to carry out our fieldwork in WantĂ©, and Aboubacar Moussa and the MEADEN for their assistance in Cameroon. Research assistance by Simon MonnĂ© and Celestin Khasah is gratefully acknowledged. Our greatest debt of gratitude is to the Duupa farmers of WantĂ© for providing the research material, for their hospitality, and for their interest in participating in our study. We thank two anonymous reviewers for valuable suggestions.
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Communicated by H. H. Geiger.
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Barnaud, A., Deu, M., Garine, E. et al. Local genetic diversity of sorghum in a village in northern Cameroon: structure and dynamics of landraces. Theor Appl Genet 114, 237â248 (2007). https://doi.org/10.1007/s00122-006-0426-8
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DOI: https://doi.org/10.1007/s00122-006-0426-8