Allal F.,CIRAD - Agricultural Research for Development |
Sanou H.,Institute dEconomie Rurale |
Millet L.,CIRAD - Agricultural Research for Development |
Vaillant A.,CIRAD - Agricultural Research for Development |
And 5 more authors.
Heredity | Year: 2011
The evolution of the savanna biome has been deeply marked by repeated contraction/expansion phases due to climate perturbations during the Quaternary period. In this study, we investigated the impact of the last glacial maximum (LGM) on the present genetic pattern of Vitellaria paradoxa (shea tree), a major African savanna tree. A range-wide sampling of the species enabled us to sample 374 individuals from 71 populations distributed throughout sub-Sahelian Africa. Trees were genotyped using 3 chloroplasts and 12 nuclear microsatellites, and were sequenced for 2 polymorphic chloroplast intergenic spacers. Analyses of genetic diversity and structure were based on frequency-based and Bayesian methods. Potential distributions of V. paradoxa at present, during the LGM and the last interglacial period, were examined using DIVA-GIS ecological niche modelling (ENM). Haplotypic and allelic richness varied significantly across the range according to chloroplast and nuclear microsatellites, which pointed to higher diversity in West Africa. A high but contrasted level of differentiation was revealed among populations with a clear phylogeographic signal, with both nuclear (F ST = 0.21; R ST = 0.28; R ST > R ST (permuted)) and chloroplast simple sequence repeats (SSRs) (G ST = 0.81; N ST = 0.90; N ST > N ST (permuted)). We identified a strong geographically related structure separating western and eastern populations, and a substructure in the eastern part of the area consistent with subspecies distinction. Using ENM, we deduced that perturbations during the LGM fragmented the potential eastern distribution of shea tree, but not its distribution in West Africa. Our main results suggest that climate variations are the major factor explaining the genetic pattern of V. paradoxa. © 2011 Macmillan Publishers Limited All rights reserved.
Davrieux F.,CIRAD - Agricultural Research for Development |
Allal F.,CIRAD - Agricultural Research for Development |
Piombo G.,CIRAD - Agricultural Research for Development |
Kelly B.,Institute dEconomie Rurale |
And 4 more authors.
Journal of Agricultural and Food Chemistry | Year: 2010
The Shea tree (Vitellaria paradoxe) is a major tree species in African agroforestry systems. Butter extracted from its nuts offers an opportunity for sustainable development in Sudanian countries and an attractive potential for the food and cosmetics industries. The purpose of this study was to develop near-infrared spectroscopy (NIRS) calibrations to characterize Shea nut fat profiles. Powders prepared from nuts collected from 624 trees in five African countries (Senegal, Mali, Burkina Faso, Ghana and Uganda) were analyzed for moisture content, fat content using solvent extraction, and fatty acid profiles using gas chromatography. Results confirmed the differences between East and West African Shea nut fat composition: eastern nuts had significantly higher fat and oleic acid contents. Near infrared reflectance spectra were recorded for each sample. Ten percent of the samples were randomly selected for validation and the remaining samples used for calibration. For each constituent, calibration equations were developed using modified partial least squares (MPLS) regression. The equation performances were evaluated using the ratio performance to deviation (RPDP) and Rp 2 parameters, obtained by comparison of the validation set NIR predictions and corresponding laboratory values. Moisture (RPDP = 4.45; R p 2 = 0.95) and fat (RPDP = 5.6; R p 2 = 0.97) calibrations enabled accurate determination of these traits. NIR models for stearic (RPDp = 6.26; Rp 2 = 0.98) and oleic (RPDP = 7.91; Rp 2= 0.99) acids were highly efficient and enabled sharp characterization of these two major Shea butter fatty acids. This study demonstrated the ability of near-infrared spectroscopy for high-throughput phenotyping of Shea nuts. © 2010 American Chemical Society.
Ndjiondjop M.N.,Africa Rice Center |
Futakuchi K.,Africa Rice Center |
Cisse F.,Institute dEconomie Rurale |
Baimey H.,IITA Benin |
Bocco R.,Africa Rice Center
Crop Science | Year: 2012
A total of 327 rice (Oryza spp.) genotypes were screened for tolerance to drought at the Africa Rice Center in Cotonou, Benin, in 2007 and 2008. Plants were subjected to full irrigation from sowing to harvest or to 21-d drought from 34 d after sowing. Drought-affected plants showed narrower leaves, reduced grain yield, and shorter stature. Tillering and plant maturity were negatively affected by drought whereas values for leaf temperature and leaf greenness were significantly higher under drought than under control condition. Under control condition, for 54% of genotypes, flowering occurred between 71 and 90 d after sowing. But under drought, flowering occurred at 90 or more days after sowing for the majority of genotypes. Significant genotype × environment interactions were observed for plant height, leaf greenness, flowering, grain yield, maturity, leaf rolling, and leaf tip burning. More traits were correlated with grain yield under drought for Oryza glaberrima Steud. than for other genotype groups. No relationship was observed between plant recovery ability and all other traits selected. More than 90% of plants evaluated resumed growth after drought in both years. TOG6208, TOG5691, TOG5591, TOG6594, and RAM122 were identify ed as best performing genotypes in terms of grain yield under drought. Their performance was similar to that of most of the 24 top yielding in terms of leaf rolling, leaf tip burning, and plant recovery after drought release. © Crop Science Society of America.
Benjaminsen T.A.,Norwegian University of Life Sciences |
Aune J.B.,Norwegian University of Life Sciences |
Sidibe D.,Institute dEconomie Rurale
Geoforum | Year: 2010
The aim of this article is to analyse the influence of commodified cotton production on soil fertility in southern Mali. From the late 1950s and until recently, production of both cash-crop cotton and food crops have increased rapidly in this region, giving it a reputation of being an African 'success story'. The flip side of this economic success is, however, said to be environmental degradation especially in terms of loss of soil fertility. We collected 273 soil samples in 19 villages located in various zones of land use intensity. In each village, the samples were collected on up to six different land use types varying with intensification. The analysis of the soil samples showed that soil fertility was highest in the sacred groves that have been protected and never cultivated. However, comparing soils under continuous cultivation and soils under fallow no clear trends in soil fertility were found. Cotton yields have declined since the early 1990s, while the total use of fertilisers has increased. This is often interpreted as proof of soil exhaustion, but there is no clear indication in this study that cotton-cereal rotation as practiced by smallholders in southern Mali reduces soil fertility. We argue that the decline in yields has been caused by an extensification process. Cotton fields expanded rapidly, due to attractive cotton prices in the 1990s, leading to falling investments per ha and cultivation of more marginal lands. These findings also have implications for a political ecology of commodity production and lead us to argue for an open-ended and empirically based 'critical political ecology'. © 2010 Elsevier Ltd.
Weber J.C.,World Agroforestry Center |
Mounkoro B.,World Agroforestry Center |
Dakouo J.-M.,Institute dEconomie Rurale
Development in Practice | Year: 2010
Native species of trees and shrubs contribute significantly to farmers' livelihoods by supplying food, medicinal products, fodder, and wood. In the case study reported in this article, this contribution to farmers' annual revenue varied from 26 per cent to 73 per cent, and was as high as US$ 650 a year for households for which agroforestry products were the primary source of revenue. Household consumption was not quantified in the study, but farmers' comments confirmed that native trees also played an important role in assuring food security, especially in the 'hunger period' when grain stores are low and farmers are waiting for the next harvest. © 2010 Taylor & Francis.