THE GEOGRAPHICAL DISTRIBUTION OF ALLELIC DIVERSITY, A PRACTICAL MEANS OF PRESERVING AND USING MINOR ROOT CROP GENETIC RESOURCES

Abstract

This paper addresses the preservation and use of minor root crop genetic resources, mostly aroids and yams. Conservation is fraught with difficulty: ex situ collections are expensive to maintain and methods for on-farm conservation have not been studied. Conventional breeding strategies present serious limitations when applied to these species. Furthermore, the evaluation and distribution of improved material are as problematical as its conservation. The similarities shared by these species regarding their domestication, breeding constraints and improvement strategies as well as farmers' needs, are briefly reviewed. Based on these biological constraints, we propose a practical alternative to current conservation and breeding strategies. This approach focuses on the geographical distribution of allelic diversity rather than localized ex situ and/or in situ preservation of genotypes. The practical steps are described and discussed. First, a core sample representing the useful diversity of the species is assembled from accessions selected for their diverse and distant geographic origins, wide genetic distances, quality, agronomic performances and functional sexuality. Second, the geographical distribution of this core sample, in vitro via a transit centre, allows the direct use of selected genotypes by farmers or for breeding purposes. Third, the distribution of genes is realized in the form of clones resulting from segregating progenies and, fourth, farmers select clones with local adaptation.