Aliou Guisse

Impact of irrigation water quality on soil nitrifying and total bacterial communities

Disturbance induced by two contrasting irrigation regimes (groundwater versus urban wastewater) was evaluated on a sandy agricultural soil through chemical and microbial analyses. Contrary to wastewater, groundwater displayed very high nitrate contents but small amounts of ammonium and organic matter. Despite these strong compositional shifts, soil organic carbon and nitrogen, nitrate and ammonium contents were not significantly different in both types of irrigated plot. Moreover, neither microbial biomass nor its activity, determined as fluorescein diacetate hydrolysis activity, was influenced by irrigation regimes. Bacterial community structure, assessed by denaturing gradient gel electrophoresis (DGGE) of 16S ribosomal DNA fragments, was also weakly impacted as molecular fingerprints shared an overall similarity of 85%. Ammonia-oxidizing bacterial community (AOB) was monitored by DGGE of the functional molecular marker amoA gene (alpha subunit of the ammonia monooxygenase). Surprisingly, no amoA signals were obtained from plots irrigated with groundwater, whereas signal intensities were high in all plots under wastewater. Among the last, compositional shifts of the AOB community were weak. Overall, impact of irrigation water quality on soil chemistry could not be evidenced, whereas effects were low on the total bacterial compartment but marked on the AOB community.

In Situ Effect of Some Tropical Litters on N Mineralization

ABSTRACT Soil nitrogen mineralization patterns were investigated under field conditions in the presence of five leaf litters of different qualities, Faidherbia albida, Azadirachta indica, Andropogon gayanus, Casuarina equisetifolia, and Eragrostis tremula. The experimentation was conducted in a tropical sandy soil in central Senegal over 12 months. No relationship could be drawn between litter quality (N content, cellulose, hemicellulose, lignin) and N mineralization during this field experimentation. By contrast, the presence of the litter modified the soil N cycle. At all sampling dates, the patterns of N mineralization were most high in litter amendment. The content of mineral N was highest in Casuarina equisetifolia amendment (17.03 μg N g−1 soil in November 2000, and 28.53 μg N g−1 soil in March 2001). Soil incubated in the absence of the different litters exhibited a different pattern of N mineralization. Net mineralization was observed when the soil had been previously submitted to the influence of Casuarina equisetifolia (4.87 μg N g−1 soil), while net immobilization was observed in the case of Azadirachta indica (8.13 μg N g−1 soil).

Phylogenetic diversity of indigenous cowpea bradyrhizobia from soils in Japan based on sequence analysis of the 16S-23S rRNA internal transcribed spacer (ITS) region.

Cowpea [Vigna unguiculata (L.) Walp.] is an important legume crop and yet its rhizobia have not been well characterized in many areas. In the present study, sequence analysis of the bacterial 16S-23S rRNA internal transcribed spacer (ITS) region was performed to characterize genetically 76 indigenous cowpea rhizobia from five different geographic regions (Okinawa, Miyazaki, Kyoto, Fukushima and Hokkaido) of Japan. The sequence analysis clustered all isolates in the genus Bradyrhizobium. They were conspecific with B. japonicum, B. yuanmingense, B. elkanii and Bradyrhizobium sp., although none of them grouped with B. liaoningense, B. canariense, B. betae or B. iriomotense. B. yuanmingense was only isolated from the southern region (Okinawa) where it achieved the highest frequency of 69%. B. japonicum was predominant at Miyazaki, Fukushima and Hokkaido with more than 60% of the isolates. B. elkanii was mainly recorded in the southern (Okinawa: 31%, Miyazaki: 33%) and middle (Kyoto: 33%) regions. This species was present at a very low frequency in Fukushima and absent in Hokkaido in the northern area. Bradyrhizobium sp. like-strains were absent in the southern part (Okinawa, Miyazaki) but were concentrated either in the middle regions with 67% of Kyoto isolates and 28% of Fukushima isolates, and in the northern region with 40% of the Hokkaido isolates. This study revealed a geographical distribution of cowpea bradyrhizobia which seemed to be related to the differences in the environmental characteristics (soil type and soil pH, temperature, climate, moisture) of the different regions in Japan.

Biochemical composition and nutritional value of Balanites aegyptiaca (L.) Del fruit pulps from Northern Ferlo in Senegal

Balanites aegyptiaca , a forest species of socio-economic interest for rural people, was chosen to be planted in the frame-work of the Great Green Wall project in Senegal. Although in vastly demand during food scarcity period before crops harvest, the species’ fruit is poorly valued despite its important production. In this study, the fruit pulps were harvested at maturity and the biochemical characteristics were accessed in order to better understand the fruit’s nutritional value. The moisture, sugars, proteins, amino acids, ash, fat, minerals and some vitamins were determined by standard methods of analysis. The results indicated that the fruits are a good alimentary source of sugar, minerals (mainly potassium) and ascorbic acid. The pulp proteins were qualitatively balanced, but were present only in weak quantities. Its caloric value is high due to the high concentration of sugars. Low humidity should allow a fairly good postharvest fruit conservation. The dietary intake of this fruit for local people is very valuable especially in terms of nutrition. Keywords: Balanites aegyptiaca , pulp, biochemical, nutritional value African Journal of Biotechnology , Vol. 13(2), pp. 336-342, 8 January, 2014

Effect of pearl millet–cowpea cropping systems on nitrogen recovery, nitrogen use efficiency and biological fixation using the 15N tracer technique

Abstract Nitrogen is one of the most limiting nutrients for crop production in many areas of Africa. One strategy to improve yields is to choose crops with high nitrogen use efficiency (NUE) that can produce economic yields under limited water supply. Little information is available on the comparative performance of pearl millet (Pennisetum glaucum L. R. Br.) and cowpea (Vigna unguiculata L. Walp.) in sole crops and intercrops systems for the NUE of applied fertilizers. This study was conducted under field conditions at the Senegal Agricultural Research Institute from July to October 2001. Two cropping systems were used and included sole crops of pearl millet and cowpea and a millet–cowpea intercrop. 15N-labeled urea at rates of 20 kg ha−1 (sole and intercrop cowpea) and 41 kg ha−1 (sole millet and intercrop millet) was applied. Sole millet produced 6,041 kg yield ha−1 and accumulated 95.27 kg N ha−1, of which 15.30% was derived from the nitrogen fertilizer and 84.70% from nitrogen mineralized in soil. Therefore, the NUE of the fertilizer was 36.29%. In intercrop millet, sole cowpea and intercrop cowpea, the NUEs were 15.20, 45.33 and 46.00%, respectively, indicating that the use of nitrogen fertilizer significantly decreased in intercrop only for millet. However, no significant difference was observed between sole and intercrop cowpea relative to the nitrogen derived from N2 fixation. The amount of nitrogen immobilized in the soil was significantly higher in sole millet than in sole cowpea and millet–cowpea intercrop. The Land Equivalent Ratio (LER) of grains and total dry matter showed an advantage of the millet–cowpea cropping system over sole crops.

L’Observatoire hommes–milieux international Tessékéré (OHMi) : un outil de recherche pour étudier la complexité des écosystèmes arides du Sahel

In the Sahelian zone, the drought phenomenon, combined with anthropic factors (monoculture, bush fires, defect or deficit of manure, overgrazing, etc.), has seriously affected ecological great balances, involving a degradation of the natural resources as well as a fall in agricultural productions, pointing to a process of desertification. To face these challenges, in the course of the 8th ordinary session of the conference of the Heads of States of the African Union held in January 2007 in Addis Ababa (Ethiopia), 11 countries adopted the Panafrican project called the Green Great Wall (GGW). The total objective of the GGW is to contribute i) to the fight against the deserts advance, ii) to the development of the Saharan-Sahelian zones toward a durable management of the natural resources, and iii) to the fight against poverty. It deals with the construction of a set of zones of afforestation crossing the whole African continent in the long term (7000km of which are in the west). Even if some decisions in the launching phase the GGW must be taken quickly, one cannot do without investment in interdisciplinary research. In particular, associating fundamental research and applied research will allow us to ensure the success in the medium and long term of such a large-scale reforestation project. Research segmented in compartmentalized knowledge fields needed to get adequate tools, among which OHMi Tessékéré, initiated by INNEE (Centre national de la recherche scientifique [CNRS]), in partnership with UCAD, constitutes an example. This suitable scientific tool, capable of action flexibility, of self-financing capacity, anchored in civil society, ready to implement a pragmatic and local interdisciplinarity founded currently on the concept of socio-ecological system (SES), is the one we chose to conduct our studies on the Ferlo arid ecosystems.

The Orussidae (Insecta: Hymenoptera) of Africa

Abstract. The African fauna of the rare family of parasitoid wasps, Orussidae, is reviewed. Five genera with 24 valid species are recognized. Chalinus davidi Vilhelmsen n. sp. is described; the male of Chalinus albitibialis Vilhelmsen, 2005, the male of Leptorussus madagascarensis Vilhelmsen, 2007 and the female of Orussus smithi Blank et al., 2006 are described. A neotype is designated for Oryssus plumicornis Guérin-Meneville, [1849] to properly define the genus-group name Chalinus Konow, 1897. Chalinus braunsi (Enslin, 1911), C. orientalis Guiglia, 1937 and C. somalicus Guiglia, 1935 are regarded as new junior synonyms of C. plumicornis. Leptorussus kwazuluensis Vilhelmsen, 2003 is regarded as a new junior synonym of L. africanus Benson, 1955. Distribution records for specimens examined by us are listed. The Afrotropical component of the African orussid fauna shows a high degree of endemism, with two endemic genera and 13 endemic species; only Chalinus timnaensis Kraus, 1998 and Pseudoryssus niehuisorum Kraus, 1998 have a cross-Saharan distribution. In contrast, there are only three species of Orussidae occurring exclusively in North Africa. An additional six North African species also occur outside Africa, in adjacent parts of the Palaearctic. The Atlas Mountain range spanning Morocco, Algeria and Tunisia is a hotspot for orussid diversity, nine species having been recorded from there. The current Afrotropical assemblage of orussids are a result of several independently derived lineages, some possibly resulting from vicariance events dating as far back as the Late Cretaceous. The North African orussids have probably appeared as the result of several dispersal or speciation events, some putatively occurring as recently as the Pleistocene. Online Lucid interactive identification keys are available at: http://www.waspweb.org.

Pratiques paysannes de gestion des cultivars de manioc ( Manihot esculenta Crantz) au Sud du Tchad

Dans les petites exploitations familiales, les paysans detiennent un nombre important de cultivars de manioc inexploites par la recherche. L’objectif de cette etude est d’evaluer le niveau de la diversite du manioc et d’en analyser les pratiques locales de gestion. Une enquete suivant une approche participative avec des questionnaires a ete conduite aupres de 636 paysans dans 43 villages. Une importante diversite varietale a ete revelee par l’indice de Shannon (3,38). Soixante-quinze noms vernaculaires ont ete inventories. Des differences hautement significatives ont ete observees pour le nombre de cultivars qui varie de 2 a 12 par village (6 en moyenne). La variation entre menages est faible, 1 a 4 cultivars (2 en moyenne). Le nombre de cultivars disparus varie de 1 a 14 (3,81 en moyenne) par village. La perte de la diversite est en moyenne de 18,20% et varie entre 11% et 50% selon les villages. Les paysans identifient les cultivars a partir des feuilles et tiges. La productivite, le gout et la grosseur des tubercules sont les criteres prioritaires de selection. Les echanges des boutures se font entre paysans locaux (60,84%) et par des introductions individuelles (37,43%). Ces connaissances seront integrees dans le programme d’amelioration varietale. Mots cles : Diversite varietale, conservation in situ, taxonomie locale, criteres d’identification.