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Ex-situ collections of vegetatively propagated root crops are difficult to maintain in developing countries. On-farmconservation could be a solution but is more complex for vegetatively propagated than for sexually propagated species. In Vanuatu, a Melanesian archipelago where yam, taro, sweet potato and cassava are staples, a study was undertaken to develop an on-farm conservation system based on the geographic distribution of allelic diversity. Two years after the introduction of new varieties, a survey was conducted with 449 farmers located on 10 different islands. In order to evaluate on-farm conservation efficiency, qualitative and quantitative investigations were conducted and data were analysed. The conclusion was that farmers do enrich their varietal portfolioswith introduced exotic genotypes thus broadening the narrow genetic bases of some species. Nevertheless, no local varieties were lost. Significant geographic distribution of clones of new varieties throughout the archipelago also took place via spontaneous, informal distribution to farmers' relatives. These encouraging results point to the potential impact of the geographic distribution of allelic diversity on smallholders' varietal portfolios. On-farm conservation appears to be an appropriate strategy for the conservation of root crop germplasm diversity inVanuatu. Potential applications for transfer of the methodology to other locations are discussed. (Résumé d'auteur)