However, the existing capital is likely to shrink as a result of human activity, in terms of socioeconomic development and environmental changes, particularly climate change. While there have been very few large-scale studies of the issue to date, CIRAD and its partners are beginning to reap the first results of a project funded by the Institut français de la biodiversité (IFB). The aim is to assess the changes in spatial and temporal distribution of millet and sorghum diversity in Niger between 1976 and 2003, ie over roughly a quarter of a century.
The areas cultivated and the human population in Niger have doubled in 25 years. There has also been a significant rural exodus. Moreover, the country has seen a marked change in its climate: the 400 mm isohyet has shifted 200 km south in western Niger and 100 km south in the East. The stage appears to be set for genetic erosion of plant species, but is this in fact the case for millet and sorghum?
To answer that question, researchers collected cultivated millet and sorghum varieties in 2003 from 79 villages throughout the zones in which these cereals are grown. Some 609 millet samples and 742 sorghum samples had been taken from the same villages in 1976. The agromorphological and genetic diversity of the samples collected in 1976 and 2003 was compared through field trials and using microsatellite molecular markers.
The results showed that agromorphological diversity had not changed much in Niger. However, there had been changes in the geographical distribution of the various varieties, perhaps due to changing climatic and agronomic constraints, or to the emergence of new uses. Moreover, the surveys and field trials showed that the millet varieties grown in 2003 in the zones of Niger most exposed to climatic risks were generally earlier than those grown in the same regions in 1976.
Analysis by microsatellite markers, for its part, revealed that the genetic diversity of both sorghum and millet varieties had held up well. Overall, no genetic erosion was observed and the allelic wealth of the two surveys was equivalent.
These results show the ability of millet and sorghum varieties to maintain their diversity in countries like Niger, which are often victims of recurrent, severe drought. This resilience, which is boosted by the traditional seed production system, confirms the merits of growing these crops. It would be worth conducting similar studies in other Sahelian countries such as Mali or Burkina Faso, where the changes in production systems, compounded by stronger competition from maize and cotton than in Niger, could produce different results.
Jacques Chantereau | alfa
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