Résumé
The tropical root and tuber crops (cassava, sweet potato, yams and aroids) share common biological traits. Cultivars are allogamous, heterozygous, with erratic flowering, and are asexually propagated. Breeding is based on phenotypic recurrent selection of genotypes evaluated on-station through successive clonal generations, and through multi-locational trials once there is enough clonal material. The distribution of selected clones to farmers is constrained by their low multiplication rate and the absence of a seed industry. Quality aspects are critical and improved genotypes are often rejected because they do not correspond to the stringent consumers’ expectations. Considering the socio-economic characteristics of smallholders, participatory plant breeding (PPB) and participatory variety selection (PVS) seem to be well adapted. This global review covers 35 studies related to 19 projects conducted over the last three decades. It attempts to clarify why PPB and PVS implementation is practically complex. Several constraints are identified: the heterogeneity of the clonal propagules, the need for simple and robust experimental field layouts, the necessary but difficult sensory evaluation, and the absence of breeders and farmers’ reward systems. Because of the significant GEI, most conventional breeding programs are now attempting to increase the number of sites as early as the single row and preliminary trials. We suggest that installing early seedling trials in different environments could allow farmers to be involved in the single row trial evaluation and claim ownership on the selected clones. These could be propagated on-farm, further evaluated, and returned to breeders for new cycles.