Fatty acid and tocopherol patterns of variation within the natural range of the shea tree (Vitellaria paradoxa)

The shea tree, Vitellaria paradoxa, is one of the most economically and culturally important indigenous tree species in the Sudano-Sahelian region. Its seeds contain a vegetable fat, internationally known as shea butter, which is widely used in edible, cosmetic and pharmaceutical sectors. Based on samples from 456 trees distributed in 17 locations across the species natural range from Senegal to Uganda, the fatty acid and tocopherol variation, and its relationship with geographic and climatic variables, was assessed in order to address the pattern and the origin of this variation across the natural range. Significant differences between Western and Eastern regions for oleic, stearic acid, saturated–unsaturated acid ratio and γ-tocopherol were identified that it is postulated maybe a result of genetic drift due to the evolutionary history of shea tree populations. Within regions the difference among stands was significant for most constituents; however the major part of the variation was observed among trees within stand (53–90 %). Relationships with climatic variables were not verified, weakening evidence for clinal variation hypotheses suggested by previous studies.     

Characterisation of the lymph node immune response following Mycoplasma mycoides subsp. Mycoides SC infection in cattle

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides biotype Small Colony (MmmSC), is still a major cattle disease in Africa. Development of long-term protective vaccines, the only relevant strategy to achieve CBPP eradication, requires the characterisation of the protective immune mechanism. To this aim, the present study investigated the cellular immune response persisting in the lymph nodes of cattle infected naturally and experimentally by contact, one year post exposure. The lymph node cell composition, MmmSC responsiveness and phenotype of the MmmSC-responding lymphocytes were compared between animals according to the different outcomes of the infection. To unravel the protective mechanism, the study focussed on the MmmSC-specific memory immune response generated in recovered cattle, known to develop long-term immunity and to be resistant to reinfection. An MmmSC-specific immune response, mediated by IFNgamma-secreting CD4 T-cells, was detected in the lymph nodes of all recovered cattle. Furthermore, the magnitude of this immune response was significantly higher in animals with complete recovery than in recovered animals presenting lung sequestra. The findings suggest that, in recovered cattle, a subset of MmmSC-primed IFNgamma-secreting CD4 T-cells homed to the regional lymph nodes as MmmSC-specific memory T-cells, likely responsible for the protective anamnestic response. Induction and expansion of this subset of MmmSC-specific CD4 memory T-cells might be a major goal to develop efficient long term protective vaccines against CBPP.     

Trenching: A Necessity for Assessment of N ² Fixation in Field Grown Faidherbia albida Using N-Enrichment Methodology

In Senegal at Nioro experimental station the 15 N 2 isotope dilution technique was used at field conditions for estimating fixation of N 2 in Faidherbia albida, mono cultured and mixed with the reference species, Parkinsonia aculeata. Trenched and nontrenched plots within the plantation were labeled with 15 N 2 - ammonium sulphate containing 2 atom % 15 N excess at the equivalent amount of 20 kg N ha -1. The proportion of fixed N 2 was lower than that previously measured in experiments using Parkia biglobosa as a reference tree species: 20.3% vs. 54.7%. This difference might be due to physiological differences between the two reference species. Significant effect of trenching vs. nontrenching to the labeled area was observed on the percentage of N 2 derived from atmosphere (% Ndfa) of F. albida. The % Ndfa was higher in trenched than in nontrenched labeled area (+ 34.3%). There was no difference however in the amount of N 2 fixed in trenched and nontrenched plots although the estimate in the former (6.70 2 g N plant -1) was slightly higher than that in the later (5.60 g N plant -1). Thus trenching the labeled area seems to be necessary for estimating the N 2 fixed by F. albida in the field.     

Policy and Legal Frameworks Governing Trees: Incentives or Disincentives for Smallholder Tree Planting Decisions in Cameroon?

Agroforestry and planting trees on farmers’ fields have been reported as important elements in a strategy to meet the millennium development goals of poverty reduction and climate change improvement. However, their uptake seems to be constrained by factors both internal and external to the household and related to the policy and legislative environment. This paper examines the impact of these factors on farmers’ decisions to plant trees. Cameroon is used as a case to analyse whether existing policies and legislation governing trees support or discourage tree planting, using qualitative content analyses. Although their mission papers and statements suggest most national government policies in Cameroon address tree planting and agroforestry, actual legislation designed to follow up the policies mostly contradicts the poverty reduction goals. Often legislation and regulations are more conservation-oriented and do not provide a clear procedure to distinguish between products from trees found in the wild and those gathered from farmers’ fields.     

Farmers’ practices,utilization, conservation and marketing of Bambara groundnut (<Emphasis Type="Italic">Vigna subterranea</Emphasis> (L.) Verdc.) in Dosso Region,Western Niger

Bambara groundnut (Vigna subterranea (L.) Verdc.) is one of the important legume crop grown in marginal soils of sub-Saharan Africa. Despite its importance in food security and income generation for small scale farmers, it remains as a neglected and underutilized crop and the productivity is very low in the field due to the lack of improved varieties and lack adequate farming practices. Thus, the aim of this study is to investigate all aspects related to its production including source of seeds supply and farmers management practices, utilization, conservation and marketing. The results revealed that in this Region of Western Niger Bambara groundnut was mainly produced by female (95%) compared to male (5%). Farmers use their own recycled seed (80%) which is the main source followed by provision of recycled seeds by relatives (5%) and purchasing from the local market (15%). Also, this finding shows that there is a lack of adequate farming practices and the crop is mostly produced on inherited land without any inputs as reported by 80% of the respondents. Mono-cropping is mainly practiced by 97% of farmers while a few of them do rotation (2%) and most of pre and postharvest handling technologies are traditional. The most important traits preferred by Bambara farmers is seed colour (cream color), followed by high grain yield, early maturity and cooking ability according to the respondents with 98, 92, 88 and 72% respectively. Several features have to be taking into account in order to promote Bambara nut including its ability to do well in harsh conditions, its nutritional benefits, and its ability to fix nitrogen, thereby increasing soil fertility in mixed cropping systems.     

SUSTAINABLE DEVELOPMENT OF CROP-LIVESTOCK FARMS IN AFRICA

Crop-livestock farms across Africa are highly variable due to in agroecological and socioeconomic factors, the latter shaping the demand and supply of livestock products. Crop-livestock farms in Africa in the 20-first century are very different from most mixed farms elsewhere in the world. African crop-livestock farms are smaller in size, have fewer livestock, lower productivity and less dependency on imported feed than farms in most countries of Europe, the Americas and the intensive agricultural systems of Asia. This paper discusses the role African crop-livestock farms have in the broader socio-agricultural economy, and how these are likely to change adapting to pressures brought on by the intensification of food systems. This intensification implies increasing land productivity (more food per hectare), often leading to more livestock heads per farm, producing fertilized feeds in croplands and importing feed supplements from the market. This discussion includes (1) the links between crop yields, soil fertility and crop-livestock integration, (2) the increasing demand for livestock products and the land resources required to meet to this demand, and (3) the opportunities to integrate broader societal goals into the development of crop-livestock farms. There is ample room for development of crop-livestock farms in Africa, and keeping integration as part of the development will help prevent many of the mistakes and environmental problems related to the intensification of livestock production observed elsewhere in the world. This development can integrate biodiversity, climate change adaptation and mitigation to the current goals of increasing productivity and food security. The inclusion of broader goals could help farmers access the level of finance required to implement changes.     

Assessing the vulnerability of selected sorghum lines from the United States of America to long smut (Sporisorium ehrenbergii Vánky) disease

Long smut is a limiting factor in sorghum productivity in some countries and therefore, a threat to food security. Long smut (Sporisorium ehrenbergii Vánky) disease response was assessed in experiments on 51 sorghum accessions including 31 commercial hybrids and 20 cultivars from the United States of America (USA) in 2004 and 2005 at the Agronomic Research Stations in Bambey and Nioro, Senegal, West Africa. The highest disease incidence of 44.33% in 2004 and 16.47% in 2005 was observed in hybrid A425, and no infection was noted in hybrids 3552 and A571 in 2005 at both locations. Hybrids 730, 837, P84552, TR438, TR65G, and Wac660 exhibited low levels of infection. Among the cultivars and parental lines, SRN39 recorded the highest disease incidence of 48.0% followed by B.Tx623 with 45.8%, whereas B.9612 and R.9645 consistently recorded low levels of infection. These two cultivars B.9612 and R.9645 may possess genes for long smut resistance. All other promising sorghum cultivars and parental lines to be released/registered in the USA exhibited varied levels of susceptibility. In order to establish the sources of long smut resistance, it is of paramount importance to conduct additional screenings of aforesaid hybrids/lines in a wide spectrum of selections that would be carried out under varied environmental conditions.     

Biodiversity field trials to inform reforestation and natural resource management strategies along the African Great Green Wall in Senegal

Forest restoration is carried out with varying objectives in mind, one of which is biodiversity conservation. The present study examines the extent by which tree biodiversity could potentially be maximized in the context of the pan-African Great Green Wall for the Sahara and the Sahel Initiative (GGW). Towards this end, ten indigenous tree species were selected for study in the Ferlo region in Northern Senegal based on previous ethnobotanical studies in the zone. The species included Acacia senegal, Acacia nilotica, Acacia tortilis subsp. raddiana, Acacia seyal, Adansonia digitata, Balanites aegyptiaca, Dalbergia melanoxylon, Sclerocarya birrea, Tamarindus indica and Ziziphus mauritiana. Germination experiments were first performed in the laboratory on seed lots from Senegal, Burkina Faso, Kenya, and South Africa prior to in situ sapling production in the nursery in Northern Senegal situated along the GGW. A split plot field design was employed and the effects of seed provenance (two per species) and the addition of organic fertilizer at the timing of planting were determined. Over the course of the 2 year experimental period, the newly planted trees, in addition to the naturally regenerating woody vegetation and herbaceous grasses were monitored in the fenced-in experimental field plot. Of the ten species, only B. aegyptiaca, A. tortilis subsp. raddiana, and S. birrea exhibited moderate survival rates. The effects of provenance and fertilizer addition were sporadic and species-dependent. Natural regeneration of woody species was abundant albeit characterized by low biodiversity whereas herbaceous grass species showed extensive biodiversity, especially under tree canopies as compared to open areas.     

Controlled ectomycorrhization of an exotic legume tree species Acacia holosericea affects the structure of root nodule bacteria community and their symbiotic effectiveness on Faidherbia albida, a native Sahelian Acacia

Many fast growing tree species have been introduced to promote biodiversity rehabilitation on degraded tropical lands. Although it has been shown that plant productivity and stability are dependent on the composition and functionalities of soil microbial communities, more particularly on the abundance and diversity of soil symbiotic micro-organisms (mycorrhizal fungi and rhizobia), the impact of tree introduction on soil microbiota has been scarcely studied. This research has been carried in a field plantation of Acacia holosericea (Australian Acacia species) inoculated or not with an ectomycorrhizal fungus isolate, Pisolithus albus IR100. After 7 year's plantation, the diversity and the symbiotic properties of Bradyrhizobia isolated from the plantation soil or from the surrounding area (Faidherbia albida (Del.) a. Chev. parkland) and able to nodulate F. albida, a native Sahelian Acacia species, have been studied. Results clearly showed that A. holosericea modified the structure of Bradyrhizobia populations and their effectiveness on F. albida growth. This negative effect was counterbalanced by the introduction of an ectomycorrhizal fungus, P. albus, on A. holosericea root systems.In conclusion, this study shows that exotic plant species can drastically affect genotypic and symbiotic effectiveness of native Bradyrhizobia populations that could limit the natural regeneration of endemic plant species such as F. albida. This effect could be counterbalanced by controlled ectomycorrhization with P. albus. These results have to be considered when exotic tree species are used in afforestation programs that target preservation of native plants and soil ecosystem rehabilitation.