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Implications for in situ genetic resource conservation from the ecogeographical distribution of rice genetic diversity in Maritime Guinea

Barry M.B., Pham J.L., Noyer J.L., Courtois B., Billot C., Ahmadi N.. 2007. Plant Genetic Resources, 5 (1) : p. 45-54.

DOI: 10.1017/S1479262107390898

Genetic resource conservation is widely acknowledged as important. The implementation of conservation requires an insight into the distribution of genetic diversity at the scale of small regions or villages. We present an analysis of rice diversity at such a scale, in a region where traditional farming still prevails. Regional allelic diversity was comparable to that noted worldwide for Asian rice (Oryza sativa), but not as high for African rice (O. glaberrima). Each village pooled more than half of the regional allelic diversity. Genetic differentiation between varieties from the same village accounted for 70% of the regional variation. The differentiation associated with lowland and upland rice-growing ecosystems was 23%, while that associated with differences between villages within the same ecosystem was 7%. In the upland ecosystem, geographical distance had a significant effect on the FST between pairs of villages. In the lowland ecosystem, differences in soil salinity between villages affected FST. Genetic diversity within a single village may have up to three components: an ancient glaberrima component shared with neighbouring or ethnically related villages; a relatively ancient sativa component which was hardly or no longer shared with other villages due to local differentiation; and a recently introduced sativa component shared with other villages. Genetic resource conservation could be achieved, in terms of allelic diversity, through stratified sampling according to described genetic differentiation factors, whereas current farming systems must be preserved to ensure conservation of the diversity of allelic associations.

Mots-clés : oryza glaberrima; oryza sativa; conservation du matériel génétique; distribution géographique; biodiversité; variété indigène; identification; guinée

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