Genetic characterization of traditional fonio millets (Digitaria exilis, D. iburua STAPF) landraces from West-Africa : Implications for conservation and breeding

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AdoukonouAwoSagbadjaHubert_2010_10_19.pdf (3.63 MB)

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2010

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http://dx.doi.org/10.22029/jlupub-17034

Abstract

Fonio millets (Digitaria exilis, D. iburua) are amongst the important indigenous cereal crops that greatly contribute to household food security in semi-arid and sub-humid drought-prone areas of West-Africa. Because of their complete scientific neglect, the potential of these crops for food and agriculture is not adequately exploited for improvement. This thesis therefore deals with the genetic characterization of fonio genetic resources with the overall objective to contribute to our knowledge on the biology and genetics of the crops. In the primary step of the study, a basic cytogenetic evaluation of fonio millets and some of their wild relatives was conducted. The genome size among these Digitaria taxa was variable, while its stability was evident within species. Besides, the longstanding hypotheses on cytological variability in fonio was not substantiated as the crops were found to be exclusively tetraploid with 2n=36 chromosomes. AFLP analysis supplemented by agro-morphological traits evaluation was further performed to quantify the genetic diversity in fonio crops and assess its population structure and geographical pattern of distribution. Globally, a relatively moderate to extremely narrow genetic background was detected in these crops, which need due attention from a conservation and breeding point of view. In D. exilis, the genetic diversity was structured and unequally distributed in the region. The genetic variability and phenotypic attributes were loosely correlated. Based on AFLP markers, the molecular phylogenetic relationships of fonio species with the wild relatives were also inferred. Previous view of direct domestication of D. exilis and D. iburua from the wild tetraploid D. longiflora and D. ternata, respectively, was confirmed. In the last step of the study, progeny analysis by both AFLP and isozymes, seed set determination and pollen viability test were conducted to determine the reproductive system in fonio millets. Apomixis was found to be the major (if not the absolute) mode of reproduction in these crops. The present work constitutes the first large scale genetic characterization of West-African fonio millets and substantially adds to the general scientific understanding of the crops. The diverse results obtained are relevant for conservation management and exploitation of fonio genetic resources in breeding that, ultimately, may boost fonio production in West-Africa.

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