Gestions locales et dynamiques régionales de la diversité variétale du manioc en Amazonie

摘要

Cassava is the staple food crop of the great majority of Amazonian populations. Depending on the region and on the type of population (Amerindians, mixed, or recent immigrants), a more or less high diversity of manioc varieties are grown, ranging from two to three varieties per farm to 30 or more. Strategies for conserving genetic resources of manioc must be based on firm understanding of the genetic base of this diversity and on how this diversity is produced and maintained. The comparative research we have conducted incorporates genetic, ecological, ethnobiological and social-anthropological approaches, and aims to elucidate the causal links between varietal diversity, agricultural practices and associated representations, and socio-economic environment. Genetic analyses have demonstrated a high degree of polymorphism, both within and among varieties. Results of ethnobiological studies have also shown that cultural groups vary in the value attached to varietal diversity, as revealed both in the patterns of circulation of propagation material (stem cuttings) and the place given to manioc originating from spontaneous seedlings. In addition to these factors affecting local dynamics, more global dynamics - increasing commercialisation of flour, changing food habits, and changing agricultural policies - also affect varietal diversity. These factors tend to reduce the number of varieties cultivated and to modify the structure of diversity. Our results suggest the utility of developing regional poles of conservation, which can extend or complement the centralised structures now in place.