Aïssata Mamadou

Bio: Aïssata Mamadou is an academic researcher from Institut national de la recherche agronomique. The author has contributed to research in topics: Genetic diversity & Germplasm. The author has an hindex of 5, co-authored 8 publications receiving 341 citations.

Diversity of wild and cultivated pearl millet accessions (Pennisetum glaucum [L.] R. Br.) in Niger assessed by microsatellite markers

Abstract: Genetic diversity of crop species in sub-Sahelian Africa is still poorly documented. Among such crops, pearl millet is one of the most important staple species. In Niger, pearl millet covers more than 65% of the total cultivated area. Analyzing pearl millet genetic diversity, its origin and its dynamics is important for in situ and ex situ germplasm conservation and to increase knowledge useful for breeding programs. We developed new genetic markers and a high-throughput technique for the genetic analysis of pearl millet. Using 25 microsatellite markers, we analyzed genetic diversity in 46 wild and 421 cultivated accessions of pearl millet in Niger. We showed a significantly lower number of alleles and lower gene diversity in cultivated pearl millet accessions than in wild accessions. This result contrasts with a previous study using iso-enzyme markers showing similar genetic diversity between cultivated and wild pearl millet populations. We found a strong differentiation between the cultivated and wild groups in Niger. Analyses of introgressions between cultivated and wild accessions showed modest but statistically supported evidence of introgressions. Wild accessions in the central region of Niger showed introgressions of cultivated alleles. Accessions of cultivated pearl millet showed introgressions of wild alleles in the western, central, and eastern parts of Niger.

Changes in the diversity and geographic distribution of cultivated millet ( Pennisetum glaucum (L.) R. Br.) and sorghum ( Sorghum bicolor (L.) Moench) varieties in Niger between 1976 and 2003

Abstract: Changes in the diversity of landraces in centres of diversity of cultivated plants need to be assessed in order to monitor and conserve agrobioversity—a key-element of sustainable agriculture. This notably applies in tropical areas where factors such as increased populations, climate change and shifts in cropping systems are hypothesized to cause varietal erosion. To assess varietal erosion of staple crops in a country subjected to various anthropogenic and natural environmental changes, we carried out a study based on a comparison of the diversity of pearl millet and sorghum varieties collected in 79 villages spanning the entire cereal-growing zone of Niger over a 26 year period (1976–2003). For these two crops, the number, name and type of varieties according to important traits for farmers were considered at different spatial scales (country, region, village) at the two collection dates. The results confirmed the high diversity of millet and sorghum varieties in Niger. No erosion of varietal diversity was noted on a national scale during the period covered. Some changes were observed but were limited to the geographical distribution of certain varieties. This highlights that farmers’ management can preserve the diversity of millet and sorghum varieties in Niger despite recurrent and severe drought periods and major social changes. It also indicates that rainfed cereal cropping systems in Niger should remain to be based on millet and sorghum, while reinforcing farmers’ seed systems.

Niger-wide assessment of in situ sorghum genetic diversity with microsatellite markers.

Abstract: Understanding the geographical, environmental and social patterns of genetic diversity on different spatial scales is key to the sustainable in situ management of genetic resources. However, few surveys have been conducted on crop genetic diversity using exhaustive in situ germplasm collections on a country scale and such data are missing for sorghum in sub-Saharan Africa, its centre of origin. We report here a genetic analysis of 484 sorghum varieties collected in 79 villages evenly distributed across Niger, using 28 microsatellite markers. We found a high level of SSR diversity in Niger. Diversity varied between eastern and western Niger, and allelic richness was lower in the eastern part of the country. Genetic differentiation between botanical races was the first structuring factor (Fst = 0.19), but the geographical distribution and the ethnic group to which farmers belonged were also significantly associated with genetic diversity partitioning. Gene pools are poorly differentiated among climatic zones. The geographical situation of Niger, where typical western African (guinea), central African (caudatum) and eastern Sahelian African (durra) sorghum races converge, explained the high observed genetic diversity and was responsible for the interactions among the ethnic, geographical and botanical structure revealed in our study. After correcting for the structure of botanical races, spatial correlation of genetic diversity was still detected within 100 km, which may hint at limited seed exchanges between farmers. Sorghum domestication history, in relation to the spatial organisation of human societies, is therefore key information for sorghum in situ conservation programs in sub-Saharan Africa.

Spatio-temporal dynamics of genetic diversity in Sorghum bicolor in Niger

Abstract: The dynamics of crop genetic diversity need to be assessed to draw up monitoring and conservation priorities. However, few surveys have been conducted in centres of diversity. Sub-Saharan Africa is the centre of origin of sorghum. Most Sahel countries have been faced with major human, environmental and social changes in recent decades, which are suspected to cause genetic erosion. Sorghum is the second staple cereal in Niger, a centre of diversity for this crop. Niger was submitted to recurrent drought period and to major social changes during these last decades. We report here on a spatio-temporal analysis of sorghum genetic diversity, conducted in 71 villages covering the rainfall gradient and range of agro-ecological conditions in Niger's agricultural areas. We used 28 microsatellite markers and applied spatial and genetic clustering methods to investigate change in genetic diversity over a 26-year period (1976-2003). Global genetic differentiation between the two collections was very low (F (st) = 0.0025). Most of the spatial clusters presented no major differentiation, as measured by F (st), and showed stability or an increase in allelic richness, except for two of them located in eastern Niger. The genetic clusters identified by Bayesian analysis did not show a major change between the two collections in the distribution of accessions between them or in their spatial location. These results suggest that farmers' management has globally preserved sorghum genetic diversity in Niger.

Population genomics of sorghum (Sorghum bicolor) across diverse agroclimatic zones of Niger.

Abstract: Improving adaptation of staple crops in developing countries is important to ensure food security. In the West African country of Niger, the staple crop sorghum (Sorghum bicolor) is cultivated acro...

Drought stress adaptation: metabolic adjustment and regulation of gene expression

Abstract: Plants cope with drought stress by manipulating key physiological processes like photosynthesis, respiration, water relations, antioxidant and hormonal metabolism. There exist multiple and often redundant stress sensors, which transduce the stress signal through secondary signalling molecules to the nucleus, where the expression of stress-response genes is regulated. Transcription factors play an important role in regulating the expression of the stress-response genes. Another level of regulation of gene expression is at the epigenetic level and involves modifications either at the chromatin level or at the mRNA level. Crop plants show various adaptive and acclimatization strategies to drought stress, which range from seemingly simple morphological or physiological traits that serve as important stress tolerance markers to major upheavals in gene expression in which a large number of transcription factors are induced. Studies on contrasting crop genotypes or genetic engineering of crops help in differentiating responses to drought from those leading to drought tolerance. Of specific importance to crop plants is not whether they survive stress, but whether they show good yields under stress conditions.

The Potential Role of Neglected and Underutilised Crop Species as Future Crops under Water Scarce Conditions in Sub-Saharan Africa.

Abstract: Modern agricultural systems that promote cultivation of a very limited number of crop species have relegated indigenous crops to the status of neglected and underutilised crop species (NUCS). The complex interactions of water scarcity associated with climate change and variability in sub-Saharan Africa (SSA), and population pressure require innovative strategies to address food insecurity and undernourishment. Current research efforts have identified NUCS as having potential to reduce food and nutrition insecurity, particularly for resource poor households in SSA. This is because of their adaptability to low input agricultural systems and nutritional composition. However, what is required to promote NUCS is scientific research including agronomy, breeding, post-harvest handling and value addition, and linking farmers to markets. Among the essential knowledge base is reliable information about water utilisation by NUCS with potential for commercialisation. This commentary identifies and characterises NUCS with agronomic potential in SSA, especially in the semi-arid areas taking into consideration inter alia: (i) what can grow under water-scarce conditions, (ii) water requirements, and (iii) water productivity. Several representative leafy vegetables, tuber crops, cereal crops and grain legumes were identified as fitting the NUCS category. Agro-biodiversity remains essential for sustainable agriculture.

Millets: nutritional composition, some health benefits and processing - a review

Abstract: Millets are a major food source in arid and semi-arid parts of the world. Millets are good sources of energy.They provide protein, fatty acids, minerals, vitamins, dietary fibre and polyphenols. Typical millet proteincontains high quantity of essential amino acids especially the sulphur containing amino acids (methionine andcysteine). Processing millet by milling removes the bran and germ layers that are rich in fibre andphytochemicals, causing significant loss. The millets are source of antioxidants, such as phenolic acids andglycated flavonoids. Millet foods are characterized to be potential prebiotic and can enhance the viability orfunctionality of probiotics with significant health benefits. The nutritional significance of millets demands foran examination of the nutritional characteristics and functional properties of different millet cultivars as well asdeveloping value added products from millets.

Seed exchange networks for agrobiodiversity conservation. A review

Abstract: The circulation of seed among farmers is central to agrobiodiversity conservation and dynamics. Agrobiodiversity, the diversity of agricultural systems from genes to varieties and crop species, from farming methods to landscape composition, is part of humanity’s cultural heritage. Whereas agrobiodiversity conservation has received much attention from researchers and policy makers over the last decades, the methods available to study the role of seed exchange networks in preserving crop biodiversity have only recently begun to be considered. In this overview, we present key concepts, methods, and challenges to better understand seed exchange networks so as to improve the chances that traditional crop varieties (landraces) will be preserved and used sustainably around the world. The available literature suggests that there is insufficient knowledge about the social, cultural, and methodological dimensions of environmental change, including how seed exchange networks will cope with changes in climates, socio-economic factors, and family structures that have supported seed exchange systems to date. Methods available to study the role of seed exchange networks in the preservation and adaptation of crop specific and genetic diversity range from meta-analysis to modelling, from participatory approaches to the development of bio-indicators, from genetic to biogeographical studies, from anthropological and ethnographic research to the use of network theory. We advocate a diversity of approaches, so as to foster the creation of robust and policy-relevant knowledge. Open challenges in the study of the role of seed exchange networks in biodiversity conservation include the development of methods to (i) enhance farmers’ participation to decision-making in agro-ecosystems, (ii) integrate ex situ and in situ approaches, (iii) achieve interdisciplinary research collaboration between social and natural scientists, and (iv) use network analysis as a conceptual framework to bridge boundaries among researchers, farmers and policy makers, as well as other stakeholders.