Spatial and Temporal Variation in Selection of Genes Associated with Pearl Millet Varietal Quantitative Traits In situ

Ongoing global climate changes imply new challenges for agriculture. Whether plants and crops can adapt to such rapid changes is still a widely debated question. We previously showed adaptation in the form of earlier flowering in pearl millet at the scale of a whole country over three decades. However, this analysis did not deal with variability of year to year selection. To understand and possibly manage plant and crop adaptation, we need more knowledge of how selection acts in situ. Is selection gradual, abrupt, and does it vary in space and over time? In the present study, we tracked the evolution of allele frequency in two genes associated with pearl millet phenotypic variation in situ. We sampled 17 populations of cultivated pearl millet over a period of 2 years. We tracked changes in allele frequencies in these populations by genotyping more than seven thousand individuals. We demonstrate that several allele frequencies changes are compatible with selection, by correcting allele frequency changes associated with genetic drift. We found marked variation in allele frequencies from year to year, suggesting a variable selection effect in space and over time. We estimated the strength of selection associated with variations in allele frequency. Our results suggest that the polymorphism maintained at the genes we studied is partially explained by the spatial and temporal variability of selection. In response to environmental changes, traditional pearl millet varieties could rapidly adapt thanks to this available functional variability

Riziculture traditionnelle en Afrique de l'Ouest : valorisation et conservation des ressources génétiques

African rice Oryza glaberrima Steud. was cultivated in Africa long before asian rice was introduced to the continent. Traditional african rice is still growing today to meet special climatic and agricultural conditions. Indeed the different landraces and farming techniques are just as diverse as those associated with asian rice. Numerous specimens have been collected through field trips. An evaluation of their genetic resources shows how important it is to preserve this species and the contribution it can make to the alimentary self-sufficiency of certain ethnic West African groups.Un riz d'origine africaine, Oryza glaberrima Steud., était cultivé bien avant l'introduction du riz asiatique en Afrique. Cette riziculture traditionnelle existe encore aujourd'hui pour répondre à des exigences climatiques et culturelles particulières. Elle montre, tant en ce qui concerne les variétés que les techniques culturales, une diversité qui peut être comparée à ce que l'on observe pour le riz asiatique. Cette espèce de riz cultivé d'origine africaine a fait l'objet de nombreuses collectes permettant de rassembler des ressources génétiques. Leur évaluation montre combien il est nécessaire de les conserver et combien leur exploitation peut être utile à certains groupes ethniques d'Afrique de l'Ouest pour assurer leur autosuffisance alimentaire.Bezançon Gilles. Riziculture traditionnelle en Afrique de l'Ouest : valorisation et conservation des ressources génétiques. In: Journal d'agriculture traditionnelle et de botanique appliquée, 37ᵉ année, bulletin n°2,1995. pp. 3-24