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Ressources génétiques des mils en Afrique de l’Ouest

 | 
Gilles Bezançon
, 
Jean-Louis Pham

Abstracts

Texte intégral

1J.-P. Guengant and M. Banoin: “Pearl millet, demography and food security in Niger”

2Millet is the cereal best adapted to arid and semi-arid zones. It still constitutes, along with sorghum, the staple food of the diet of Sahelian populations, for whom it remains an uncontested plant of civilisation. However, with a demographic growth of over 3 percent a year, most Sahelian populations are today in a state of chronic food shortage. This is the case in Niger, where the trend in national cereal production is a deficit of about 20 percent.

3The cereal needs of Niger population will double between now and the year 2020, and by the year 2050 will have grown by 4 or 5 times. At current rates, the national production of cereals, 80 percent of which is millet, is far too low to cover these needs. Rapid increase of yields and a deceleration of demographic growth are more than ever necessary to avoid massive recourse to food imports and to food aid.

4Key words: Pearl millet — Niger — Food needs — Food security.

5B. Ouendeba and S.B. Siaka: “Pearl millet [Pennisetum glaucum (L.) R. Br.] in Niger: generalities and results in plant breeding”

6Niger Republic, located in West Africa where pearl millet originated, has a large genetic diversity that could be used in the development of productive cultivars essential to meet the needs of the increasing population. The variability among the landraces is important when developing gene pools with large genetic variability. Based on the last survey made in 1990, we can classify the pearl millet landraces into 3 groups: (1) pearl millets from oasis, (2) short headed and (3) long headed pearl millets.

7Pearl millet, the most widely grown cereal in Niger, is tolerant to drought, to low soil fertility and to low soil pH. Each year, more than 5 millions hectares are planted with an average yield of 400 kg/ha and a total production of 2 millions tons. The research activities implemented by IRAT, INRAN and ICRISAT have, through mass selection and recurrent selection, led to the development of varieties performing better than local varieties in favorable growing conditions. ICRISAT recent research activities on heterosis, led to the development of adapted male-sterile lines tolerant to downy mildew; promising hybrids from the male sterile lines were tested on station and on farmers’fields.

8The development of productive cultivars will play a key role in the process of food security and on farmers’incomes because of the high demand of millet-based products in urban areas.

9Key words: Pearl millet — Niger — Plant breeding — Landraces — Hybrid varieties

10M. Kouressy, M. Vaksmann, O. Niangado and M. Sanogo: “Valorization and preservation of pearl millet genetic diversity in Mali”

11The countries of the Sudan – Sahel region are characterized by a strong climatic variability. The factors that determine the production in that area are mainly the sowing date, the choice of the variety and the scheduling of the cropping period. In this region the rainfall seasons often starts erratically and ends abruptly. The characteristics of a yearly rainfall were studied by using a simple water balance model to simulate the evolution of the soil useful water content. It was established that the duration of rainfall seasons varies from one year to the other and depends upon the starting date of rainfall.

12The photoperiodism of local millet genotype is shown when a shortening of the plant production cycle is observed, following a late planting date. The occurring of such phenomenon explains a physiological adjustment by the millet plant of its production cycle to the probable duration of the rainy season. Many genes (polygenic) that are relatively easy to be fixed within a millet population control photoperiodism in millet. The photoperiodism also lines up consistently with a strong shortening of the plant stem inter-nods.

13To face the challenge of millet crop intensification many genetic pools were created, each of them having a very large genetic base sustained by local genotypes. These populations will be grown in different environments with the aim to identify those with best specific adaptations.

14Key words: Mali — pearl millet — photoperiodism — plant breeding — genes pools.

15K. vom Brocke, E. Weltzien, A, Christinck, T. Presterl, V. Hoffmann and H.H. Geiger: “Diversity study of pearl millet landraces in Rajasthan (India)”

16Pearl millet (Pennisetum glaucum [L.] R. Br.) is the staple food and fodder crop of Rajasthan in northwest India. Using amplified fragment length polymorphism (AFLP), this study investigated pearl millet genetic diversity patterns and related the results to farmers’local knowledge and seed systems. Thirty-nine cultivars were assessed: 14 farmer landraces from western Rajasthan, 13 farmer landraces from eastern Rajasthan, and 12 control cultivars. According to farmers, the same pearl millet landrace type grows across all of western Rajasthan. In eastern Rajasthan, on the other hand, farmers distinguish between several different morphological landraces that are commonly named after their village of origin. Analysis of molecular variance (AMOVA) revealed that variation within landrace populations was much higher than between regional samples. In the west, intra-village variation was higher than inter-village variation. In the east, variation between landrace groups bearing a specific name was higher than intra-group variation. Farmers’knowledge of local varieties and seed systems was, for the most part, supported by the AFLP analysis. These results are relevant for in situ maintenance and breeding strategies with a view to improving traditional varieties, specifically performance and yielding stability.

17Key words: Pearl millet — Rajasthan — Seed management — Diversity — Landraces resources.

18G. O. Omanya: “Transfer of Technology and Participatory Plant Breeding for Pearl Millet [Pennisetum glaucum (L.) R. Br.]”

19Participatory plant breeding intends to enhance the development and transfer of new or improved seeds and their accelerated adoption by fanners. Experience is drawn from a reconnaissance survey carried out in August and September 2001 in Niger, Nigeria, Mali and Burkina Faso. This survey indicated that farmers’preferred traits for pearl millet were high grain yield, early maturity, long head, compact head, high tillering, drought resistance, adaptation and taste of cooked grain. Farmers’constraints to adoption of improved varieties were lack of awareness, traditional values, seed availability, early maturity, bird damage, fertilizer cost and its availability. Farmers also cited that their main constraints to production were poor soil fertility, drought, striga, head miner attack, bird damage and lack of awareness of improved varieties and better agronomic management. The results indicate that farmers are largely unaware of improved pearl millet varieties, partly due to limited involvement of farmers in varietal development and to weak agriculture extension. This appears to delay or hinder transfer of technology, herein described as improved pearl millet varieties. Farmers were willing to take up pearl millet varieties which have their preferred characteristics. The survey emphasizes the need for scientists and extensionists to integrate farmers permanently in pearl millet varietal development and diffusion.

20Key words: West Africa — Participating plant breeding — Pearl millet — Improved varieties — Development.

21M. I. Magha: “Preservation and sustainable utilization of endangered genetic resources of pearl millet, sorghum, cowpea and sesame in Niger.”

22The author describes the genesis and content project of the «Sustainable preservation and utilization of endangered pear millet, sorghum, cowpea and sesame genetic resources in Niger». He shows how these four crops are important for the country and presents their diversity in Niger. Then, threats and consequences of loss of genetic diversity for these crops are discussed.

23The author then describes the general and specific objectives, and the outcomes of the project. Finally, the author discuss several questions about in situ conservation: patterns and strategies be used (geographical scale and kind of diversity to be considered), and their sustainability.

24Key words: Pearl millet — Sorghum — Cowpea — Sesame — Genetic diversity — Biological resources.

25K. vom Brocke, G. Trouche, M. Vaksmann and D. Bazile: “Safeguarding sorghum agrobiodiversity in Mali and Burkina Faso and landraces participating plant breeding”

26Sorghum (Sorghum bicolor (L) Moench) is the principal cereal cultivated in Burkina Faso and the second major cereal in Mali. Farmers in these countries manage a diversity of sorghum varieties for various uses. Despite of rising nutritional needs estimated for both the countries for the next twenty years, sorghum yields stay low and production increases are essentially due to an extension of the area under cultivation. Furthermore genetic erosion of sorghum landraces is observed. The objective of the present study is to reconcile maintaining sorghum biodiversity with improving its productivity. The seven stages of the project all implicate multidisciplinary teams, consisting of scientists, development workers, ONGs and farmer organisations working in a participatory manner. The latter have the majority in the instances of decision making and implementation. The aim of the project is to develop a range of diverse new sorghum varieties. These varieties should be productive and adapted to the local climatic conditions as well as to farmers preferences and needs. Their diffusion would permit the maintenance of biodiversity.

27Key words: Sorghum — Agrobiodiversity — Participatory research — In situ conservation — Landraces.

28R. G. Zangré and M. Ouédraogo: “National policies for pearl millet genetic resources conservation in Burkina Faso”

29Pearl millet genetic resources play an important role in crop production and food security in Burkina Faso. Most of millet varieties planted every year are originate from landraces developed through farmers’ traditional breeding techniques. Agromorphological and enzymatic data analyses show high levels of genetic variability in local millet ecotypes. Over the last three decades, this variability was affected by multiple unfavourable factors like repeated cycles of drought and human pressure on natural resources. The consequences of this situation are ecosystems degradation, low soil fertility, disappearance of long cycle cultivars and genetic erosion. To address this problem, a large number of countries developed policies to conduct phytogenetic resources research programmes. Despite their importance, Burkina Faso has not yet a specific policy for millet genetic resources. But some approaches and strategies based on partnership for ex and in situ conservation are taken into account.

30Ex situ conservation in Burkina involved germplasm collection through out the country with IRAT, IRD (ex ORSTOM), IPGRI, FAO, ICRISAT. From 1960 to 1999, more than 1570 samples of pearl millet ecotypes included 3 wild types were collected. This germplasm is conserved at ICRISAT (India), IRD (France) and ICPR (Canada). Agromorphological and enzymatic evaluations were done on the genetic material. Some samples are conserved in freezers at Farako-Bâ research station and used in the national breeding programme.

31In situ conservation research has been developed over the last seven years (1996). These research activities studied farmers’ knowledge related to agrobiodiversity conservation and management. One of the project activities analyses gene flow and genetic introgression between cultivated and wild millet types.

32Burkina Faso signed a large number of international, regional and sub-regional conventions and agreements related to the preservation and management of biologic resources. The last one is the Cartagena Protocole for biosafety.

33In 2002, Burkina Faso began to elaborate a national framework for phytogenetic resources.

34Key words: Approach and Strategies — Partnership — Ex situ conservation — In situ conservation — International Conventions.

35T. Robert, A. Luxereau, C. Mariac, A. Kairou, C. Allinne, A. I. Amoukou, J. Bani, M. Banoin, Y. Beidari, G. Bezançon, S. Cayeux, E. Couturon, V. Dedieu, I. Gamatché, A. Hamidou, D. Moussa, M. Sadou, M. Seydou, O. Seyni, M. Tidjani and A. Sarr: “Diversity management in farming environment: influence of anthropological factors and gene flows on genetic variability of wild and cultivated pearl millet (Pennisetum glaucum) in two places in Niger.”

36The project was settled mainly in two localities in west Niger (Zarma-Songhai region). It includes both anthropologic and genetic analyses and aims at: i) studying the relationships between farmers’ practices, gene flow and the organization of diversity at morphological and molecular levels: ii) analysing the genetic relationships between domesticated, wild and intermediate forms (soun) of pearl millet based on their genetic and morphological evaluation at the field level. The purpose was to understand the origin of so-called soun (plants with intermediate domesticated/ wild phenotypes) and to evaluate the level of introgression of cultivated populations by genes from the wild.

37The results showed that, although diverse, farmer practices favour very large genetic admixture at the village and even regional scale, through important seed flows (seed exchanges and supply networks). A consequence of this is the near-absence of any genetic differentiation (at the molecular level) between populations of the same variety cultivated by different farmers, even in remote villages. Both the abundant seed flows and the existence of a large seed bank in the soil could explain why soun are so abundant in large areas in the region, even where no wild forms are found. Moreover, the very low level of genetic differentiation between different varieties (including between early and semi–late flowering ones) can be used as a proof of the sizeable gene flow through hybridization at the field level (different varieties are often found in the vicinity of each other or even in the same field).

38Farmers are able to identify the different varieties they grow and to manage them separetely. Nevertheless, different factors act together to lead both to the homogeneization of the cultivated gene pools, and then varieties, at large geographical scales and to the existence of gene flow between domesticated and non domesticated forms of pearl millet. In particular, farmers pressures during the seed selection process cannot be neither strong nor evenly applied due to the scarcity in production. We think also they are probably less strong that they used to be; cultural practices and the largely preponderant outcrossing mating system promote hybridization between different varieties; weeding is not efficient and/or discriminant enough to remote all the soun growing in the field, so that the proportion of these plants can sometimes reach several tens per cent.

39However, it is difficult to ascertain whether we are facing a recent evolutionary process due to dramatic social and ecological (repeated drought) changes. If this were the case, this could lead to a decrease in the level of adaptation of cultivated populations to their local environment and to an increase in their introgression by genes from the wild. At the end, this could lead to a «de-domestication» of pearl millet in this region that already suffers of scarcity in the production of this crop, reinforcing therefore this situation.

40Key words: Africa — Niger — Pearl millet — Local knowledge and farmer practices — Genetic resources — Gene flow — AFLP — On farm management.

41B. Dossou, D. Balma, M. Sawadogo and D. Jarvis: “Women’s part and participation in in situ conservation process in Burkina Faso.”

42The in situ conservation approach is being experimented in Burkina Faso.

43Research was conducted to evaluate the real participation of women in the process of in situ conservation. Thus, 109 women and 48 men from four villages (Médéga, Ouahigouya, Gourga, Pobé Mengao) were surveyed. Individual and group interviews were carried out. Collected data were completed with direct observations in fields, granaries, markets, places of transformation, etc.

44The women are involved in the process of in situ conservation at several levels:

  • level of farm works: women of Burkina Faso devote more than 70% of their time to these different works: the women intervene in ploughing (30 – 45%), seedling (95%), wee–ding (40%), transportation of products (45%), shelling (90%), stocking (80%).

  • In some regions, according to their age and social rank, they intervene also in the selection, distribution, exchanges and conservation of varieties in the village and vicinities.

  • In the sector of the transformation, women are the main actors (more 95% of products are transformed by women).

45The women add value to agricultural products;

  • Women are totally in charge of seeds retail sale; the wholesale is done both by men and women.

46Women know and respect rules of conservation: plants used for preservation, the forms of the granaries, bottles, practices and good lunar periods. The women ensure the tradition and transmit it from generation to generation.

47Women, especially the Bixa in Médéga (village) have a large power to select varieties of sorghum, pearl millet, ground-nut and cowpea.

48For okra, they alone select, maintain, exchange varieties. In all visited villages, only seeds of Frafra potatoes are exclusively selected by men.

49Women of Burkina Faso address social, environmental and economical needs though their commitment and their knowhow. They get from in situ conservation direct and indirect benefits (money, protection of the environment, food security).

50Key words: Women — In situ conservation — Agrobiodiversity — Burkina Faso — Participation.

© IRD Éditions, 2004

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