title: Genetic diversity, structure, gene flow and evolutionary relationships within the Sorghum bicolor wild-weedy-crop complex in a western African region.
abstract: Gene flow between domesticated plants and their wild relatives is one of the major evolutionary processes acting to shape their structure of genetic diversity. Earlier literature, in the 1970s, reported on the interfertility and the sympatry of wild, weedy and cultivated sorghum belonging to the species Sorghum bicolor in most regions of sub-Saharan Africa. However, only a few recent surveys have addressed the geographical and ecological distribution of sorghum wild relatives and their genetic structure. These features are poorly documented, especially in western Africa, a centre of diversity for this crop. We report here on an exhaustive in situ collection of wild, weedy and cultivated sorghum assembled in Mali and in Guinea. The extent and pattern of genetic diversity were assessed with 15 SSRs within the cultivated pool (455 accessions), the wild pool (91 wild and weedy forms) and between them. F (ST) and R (ST) statistics, distance-based trees, Bayesian clustering methods, as well as isolation by distance models, were used to infer evolutionary relationships within the wild-weedy-crop complex. Firstly, our analyses highlighted a strong racial structure of genetic diversity within cultivated sorghum (F (ST) = 0.40). Secondly, clustering analyses highlighted the introgressed nature of most of the wild and weedy sorghum and grouped them into two eco-geographical groups. Such closeness between wild and crop sorghum could be the result of both sorghum's domestication history and preferential post-domestication crop-to-wild gene flow enhanced by farmers' practices. Finally, isolation by distance analyses showed strong spatial genetic structure within each pool, due to spatially limited dispersal, and suggested consequent gene flow between the wild and the crop pools, also supported by R (ST) analyses. Our findings thus revealed important features for the collection, conservation and biosafety of domesticated and wild sorghum in their centre of diversity.
authors.affiliation: CIRAD, UMR AGAP, Avenue d'Agropolis, 34398, Montpellier, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Sagnard
authors.forename: Monique
authors.initials: M
authors.lastname: Deu
authors.forename: Dékoro
authors.initials: D
authors.lastname: Dembélé
authors.forename: Raphaël
authors.initials: R
authors.lastname: Leblois
authors.forename: Lassana
authors.initials: L
authors.lastname: Touré
authors.forename: Mohamed
authors.initials: M
authors.lastname: Diakité
authors.forename: Caroline
authors.initials: C
authors.lastname: Calatayud
authors.forename: Michel
authors.initials: M
authors.lastname: Vaksmann
authors.forename: Sophie
authors.initials: S
authors.lastname: Bouchet
authors.forename: Yaya
authors.initials: Y
authors.lastname: Mallé
authors.forename: Sabine
authors.initials: S
authors.lastname: Togola
authors.forename: Pierre C Sibiry
authors.initials: PC
authors.lastname: Traoré
mesh_terms: D000349:Africa; D000483:Alleles; D001499:Bayes Theorem; D002874:Chromosome Mapping; D002980:Climate; D016000:Cluster Analysis; D003433:Crosses, Genetic; D004463:Ecology; D051456:Gene Flow; D017343:Genes, Plant / Q000235:genetics*; D014644:Genetic Variation; D005843:Geography; D016701:Guinea; D008302:Mali; D008957:Models, Genetic; D045868:Sorghum / Q000235:genetics*