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Scientific bulletin 325 - July 2009 Pearl millet, food for the future in the Sahel Pearl millet is the staple food for 50 million people living in the Sahel. It is extremely resistant to drought and well adapted to poor soils and remains the only crop that truly corresponds to the environmental conditions and traditional diet. However, harvests vary considerably depending on rainfall and soil fertility. Environmental conditions vary greatly, with drought intensifying from year to year, climate change and desertification: to confront these harsh situations in the region and ensure sufficient yields, Sahel farmers need the possibility to choose suitable varieties. Since pearl millet domestication more than 3 500 years ago, humans have thus selected some important agronomic characters and developed a great diversity of varieties, adapted to different climates. Researchers from the IRD and Abdou Moumouni University in Niamey, Niger, recently identified a gene responsible for this adaptation, called PHYC. This is one of the genes which play a role in light perception in plants. In the context of current climate change, the discovery of this key genetic factor allows the development of appropriate varieties. Left: Nigerian woman showing different varieties of millet she grows (© IRD /Cédric Mariac). Right: Millet field in Niger (© IRD /Claire Costis). Pearl millet, the staple source of energy for millions of people, is the bedrock of food security in the Sahel. It is one of the most important food crops in the region, along with two other cereals, sorghum and rice. In Niger, a major producer in Africa second only to Nigeria, pearl millet crops cover for example more than 65% of the cultivated surface area and make up three-quarters of the country’s cereal production. It is the crop plant best adapted to arid and semi-arid zones. Pearl millet has been grown for over 3 500 years all over the Sahel and the tropical countries of West Africa. The plant and its cultivation originated in Niger and Mali, diffused over equatorial Africa then towards India, thanks notably to a genetic adaptation to different climates, one of the key factors in the domestication and diffusion of cultivated millet. A gene, an adaptation What genes have humans selected over the millennia in order to cultivate millet under different climates? Researchers from the IRD and University Abdou Moumouni in Niamey, Niger, determined one of those responsible for this adaptation: the PHYC gene which plays a predominant role in the plant’s light perception. The scientists discovered a significant association between the genetic variations, from one species to another, the PHYC gene and those governing flowering time, and also certain morphological traits such as spike length and stem diameter. Flowering time was strongly linked to climatic conditions: a long flowering time was better adapted to more humid climates, a shorter one suitable for drier conditions. For example, the species cultivated in coastal tropical Africa flower in 160 days, whereas flowering in Sahelian varieties can be observed from 45 days. The genetic factors underlying the differences between these varieties were hitherto unknown. An innovative method Identification of the PHYC gene was achieved by using a novel method which takes into account the evolutionary history of millet populations. The research team first selected 90 inbred Institut de recherche pour le développement - 44, boulevard de Dunkerque, CS 90009 F-13572 Marseille Cedex 02 - France - www.ird.fr You can find the IRD photos concerning this bulletin, copyright free for the press, on www.ird.fr/indigo lines already genotyped and ran 3 field trials in Niger between 2005 and 2006 to characterize them. Flowering date, CONTACT : ramification, plant height, spike length and diameter: all the parameters were Yves VIGOUROUX, thoroughly investigated. Sequencing1 researcher at IRD was performed on eight flowering paUMR Diversité et adaptation des plantes cultivées (Dia-PC) thway genes of the lines studied. A statistical association analysis of these (IRD, AGRO_M, INRA, different genes was applied, taking Université Montpellier 2) account of the population structure and phylogenetic relationships in the Address : samples studied. Using these crosCentre IRD de Montpellier sings, which have taken place over BP 64501 thousands of years, the scientists iso34394 Montpellier cedex 5 lated highly precisely a gene highly imTel : 33 (0)4 67 41 62 45 portant for pearl millet’s adaptation to [email protected] climate. Up to now, the search for such genetic REFERENCES : factors consisted in making crosses in order to obtain hybrids and analyse the Dangles O., Carpio C., lineages thus obtained. Such genetic Saïdou A.-A., Mariac C., Luong V., Pham J.crossing made it possible to analyse L., Bezançon G. and only a small number of generations Vigouroux Y. Association of individuals and isolate only large Studies Identify Natural blocks of chromosomes. The identifiVariation at PHYC Linked cation of genes subsequently necessito FloweringTime and tates many years of supplementary reMorphological Variation in search. The new approach used in this study provides a way of considerably accelerating identification of agriculturally significant genes. Predictions of future climates in the Sahel region zone remain riddled with uncertainties. However, arid and semi-arid areas are subject to abrupt changes of climate. Thus, for 40 years, the Sahel has been experiencing a trend of rainfall decrease. Identification of pearl millet’s gene for adaptation to different climates offers a way to select and develop the varieties most appropriate for such a context of environment and climate change. Millet could therefore become spearhead in the combat against drought in the Sahel. Redaction DIC - Gaëlle Courcoux Translation - Nicholas Flay 1. Sequencing consists in determining the order of DNA nucleotides that make up genes. Pearl Millet. Genetics, 182, p. 899-910, 2009 DOI: 10.1534/ genetics.109.102756 KEY WORDS : Millet, Sahel, climate, adaptation PRESS OFFICE : © IRD / Marie-Noëlle favier © IRD / Marie-Noëlle favier Scientific bulletin 325 - July 2009 For futher information Vincent Coronini +33 (0)4 91 99 94 87 [email protected] INDIGO, IRD PHOTO LIBRARY : Daina Rechner +33 (0)4 91 99 94 81 [email protected] www.ird.fr/indigo Malian women grinding millet. Millet is still the only crop adapted to environmental conditions and people’s diet. Board illustrating the variety of mils cultivated in Niger. Did you know? The Sahel is the cradle of the domestication of pearl millet. The oldest pottery bearing representations of wild and cultivated millet were found in Mauritania 3 500 years ago. Gaëlle Courcoux, coordinator Délégation à l’information et à la communication Tél. : +33 (0)4 91 99 94 90 - fax : +33 (0)4 91 99 92 28 - [email protected]