While there has been progress in our understanding of the origin and history of agriculture in sub-Saharan Africa, a unified perspective is still lacking on where and how major crops were domesticated in the region. Here, we investigated the domestication of African yam (Dioscorea rotundata), a key crop in early African agriculture. Using whole-genome resequencing and statistical models, we show that cultivated yam was domesticated from a forest species. We infer that the expansion of African yam agriculture started in the Niger River basin. This result, alongside with the origins of African rice and pearl millet, supports the hypothesis that the vicinity of the Niger River was a major cradle of African agriculture.

This article estimates how storage losses from mold, insects, and other pests, combined with liquidity constraints, influence a smallholder farm household's decision to store maize on farm after harvest. We analyze panel data from 309 smallholders in Benin covering the 2011 and 2013 harvest seasons. Results suggest that smallholders are driven to sell at harvest time for different reasons, depending on their motivation for storing. In households that report direct consumption as their primary goal for storing maize, liquidity constraints, not storage losses, reduce the amount they store. In contrast, households that store maize with the intention of selling it later in the year appear unaffected by liquidity constraints. Instead, these households store less when they expect to lose more during storage. These results suggest that policies to provide liquidity will be more helpful in motivating storage among consumption‐oriented households. Households motivated to store for later sale will benefit from modern storage technologies that mitigate the operational costs associated with storage losses.

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In the traditional yam agricultural system, by way of an ennoblement practice, farmers select tubers from the wild for cultivation. In order to assess the impact of that practice on the genetic diversity of yam, we studied the genetic structure of yams obtained after at least 3 years of ennoblement, to which farmers gave the name of traditional varieties. Cultivated yams do not always have the same genotype as homonymous traditional varieties. For the first time, we demonstrated selection by farmers through the ennoblement of genotypes found in neighbouring villages. Their adoption has a double impact: it allows an increase in the polyclonality of varieties and an indirect exchange of yam tubers between farmers. We also demonstrated that wild yams and hybrids between wild and cultivated yams are also selected. However, their adoption seems less frequent, suggesting selection and valuation of ennobled yams before integration into the cultivated pool. Finally, the adaptive advantage of wild and hybrid yams and their role in yam agrosystems are discussed. (Résumé d'auteur