Micropropagation of a West African wild grape (Lannea microcarpa)

The propagation of Lannea microcarpa (an African wild grape) by seeds causes considerable variation in the offspring, making very difficult the selection, and multiplication of superior genotypes of interest. The species is also very difficult to propagate using conventional asexual technique. Therefore, micro cutting explants of young shoots from seedlings of Lannea microcarpa were grown in vitro on semi-solid Woody Plant Medium (WPM) supplemented for each experiment with three cytokinins at seven different concentrations for shoot formation and development. The cytokinins tested were 2iP (2-isopentenyladenine), TDZ (Thidiazuron), Zea (Zeatin) plus 0.05 µM IAA in the medium. Two subcultures were performed at 35 days interval after the initial in vitro culture establishment. Shoot development occurred primarily from axillaries buds formation that was greatest on a medium containing 56 µM of 2iP (plus 0.05µM IAA), with an average number of 4.5 ± 0.3 shoots per single node cutting and an average length of 4.7 ± 0.7 cm. After removal from culture, the shoots were induced rooting using IAA (Indole-3-Acetic Acid) and IBA (1H-indole-3-butanoic acid) at seven different concentrations. Shoots rooted in response to treatment with auxins (IBA and IAA) in the WPM medium and also in talc. The WPM medium produced an average number of 7 ± 0.5 roots per cutting at 32 µM IBA and with nearly 4.5 ± 0.7 cm in length. But the 1.5% of IBA in talc gave a better result with a higher number of 7.5 ± 0.4 roots per cutting with 5.5 ± 0.6 cm in length. The objective of this study is to develop a reproducible protocol for the rapid propagation of Lannea microcarpa in a semi-solid WPM medium supplemented with various concentrations of hormones.Keywords: In vitro propagation, Sahelean tree, Cytokinins, auxins

Quelques paramètres biologiques de Orseolia oryzivora H. & G. (Diptera: Cecidomyiidae) au Burkina Faso

La cecidomyie africaine du riz, Orseolia oryzivora Harris & Gagne est lfun des principaux insectes ravageurs du riz dans plusieurs pays dfAfrique tropicale dont le Burkina Faso. De nombreux travaux ont ete realises sur lfinsecte mais jusqufici, certains parametres biologiques du diptere nfont pas encore ete explores. Ce travail a ete realise pour permettre  dfameliorer la connaissance du Nematocere dans une perspective de gestion. Ainsi, le developpement post-embryonnaire, la fecondite  potentielle, la fertilite et la sex-ratio de lfinsecte ont ete investigues. Cette etude a ete realisee a Bobo-Dioulasso, dans des cages de dimensions 60 x 90 x 65 cm et dans des conditions proches de celles de la nature. Les stades pre-imaginaux de lfinsecte ont ete prepares, conserves dans lfalcool 70 ‹ et photographies a la loupe binoculaire. La fecondite potentielle moyenne etait de 300 oeufs (192 a 404 oeufs). La fertilite moyenne individuelle etait de 36 descendants des 2 sexes. Les  descendants etaient constitues en majorite de femelles mais la distribution des males etait plus homogene. La sex-ratio obtenue a partir dfindividus sauvages etait de 1: 2,24. La larve neonate, a lfeclosion, mesurait 540 ƒÊm et comportait une petite capsule cephalique. Sur la face ventrale de la jeune larve, dans la partie anterieure a chaque segment, etaient disposees plusieurs rangees paralleles de petits tubercules cuticulaires. La pupe etait libre, elle etait depourvue de cocon. Les ebauches alaires et pedieuses etaient nettement visibles.Mots cles : Cecidomyie, fecondite, fertilite, sex-ratio, developpement

Analyse des déterminants de la demande en poisson des ménages au Burkina Faso: cas du milieu rural (Vallée du Kou) et du milieu urbain (Bobo Dioulasso et Ouagadougou)

Analysis of the Determinants of Households'Fish Demand in Burkina Faso: the Case of a Rural Area (Vallée du Kou) and Urban Areas (Bobo-Dioulasso and Ouagadougou). A study was conducted in 2004 in Burkina Faso in order to analyze the determinants of households' fish demand in both rural (Vallée du Kou) and urban (Bobo-Dioulasso and Ouagadougou) areas. To achieve this objective, 535 households were surveyed, the data collected were analyzed and a double-log regression function was constructed. The results of this study showed that households' fish consumption varied considerably according to the area (rural or urban). Households' fish demand was influenced by the availability of the product in the market. In addition to that, when the fish supply frequency increased, the duration of the conservation of the product was reduced or was annulled. The study revealed that the determinants of fish demand in rural area in Vallée du Kou included the size of the household, the prize of the fish in the market, the level of education and the revenue of the head of the household. In urban areas, these determinants include mainly the revenue of the head of the household, fish supply frequency, and conservation methods of the product

Amélioration de la disponibilité du phosphore par la gestion de la macrofaune du sol : cas d’un lixisol en zone semi-aride du Burkina Faso

La carence en phosphore des sols de l’Afrique de l’Ouest constitue une contrainte majeure à l’intensification des systèmes de production agricole. Cette étude a été conduite pour évaluer les effets de l’interaction entre la macrofaune et des technologies de gestion de la fertilité des sols sur la disponibilité du phosphore d’un lixisol en zone semi-aride du Burkina Faso. Un dispositif expérimental en split-plot comprenant deux traitements principaux (parcelles avec et sans macrofaune) et cinq technologies de gestion de la fertilité des sols a été utilisé. La disponibilité du phosphore a été évaluée en utilisant la méthode Bray I. Les résultats montrent qu’il y a une interaction positive entre les technologies de gestion de la fertilité et la macrofaune du sol. La présence de la macrofaune a entraîné une augmentation significative du phosphore assimilable du sol. De même, l’apport de compost seul ou combiné à l’urée, augmente significativement la teneur en phosphore assimilable du sol. Ces résultats suggèrent de repenser les stratégies de protection des cultures, en réduisant et en utilisant de façon judicieuse les pesticides chimiques de synthèse. Les producteurs doivent en effet, adopter les biopesticides et les pesticides naturels afin de préserver la diversité biologique des sols agricoles.Mots clés : Macrofaune, qualité de la matière organique, phosphore assimilable, interaction Burkina Faso

Cumulative effects of 20 years of fire, grazing and selective tree cutting on soil water infiltration in sudanian savanna-woodland ecosystem of West Africa

Structural and functional dynamics of savanna-woodland ecosystems are mainly shaped by fire, grazing and wood removal which effects depends both on their intensities. The long-term effects of those disturbances on key soil parameters are still largely unknown. We studied the cumulative effect of 20 years of early fire, grazing and selective tree cutting on soil water infiltration at two experimental sites with contrasting soil conditions (deep silty-clay versus shallow silty-sand) in the sudanian savanna-woodland ecosystems of Burkina Faso. Measurements were carried with a single ring infiltrometer at intervals of 5, 10, 20 and 30 minutes. Results showed that Grazing had negative effect at both sites (P<0.0001). Fire has no effect on infiltration rate at deep soil whereas it has a negative effect on shallow one. Selective wood cutting had beneficial effects for infitration rate at the site with shallow soil. Further, all combined effect of the diffreent treatment resulted in decrease infiltration rate as compared with the control (interaction exclosure, no cutting and no fire). The result suggested that projects which aim to manage or improve soil water properties must take in consideration occurrence of disturbances, soils type and avoid disturbance interaction mainly in shallow sandy soils.Keywords: Disturbances, soil water properties, Burkina Faso, soil compaction, early fire, savanna ecosystem

Effet de la macrofaune et des modes de gestion de la fertilité sur le carbone d’un lixisol au Burkina Faso

La matière organique du sol est un élément déterminant de l’activité biologique, pour laquelle, la macrofaune du sol constitue un facteur important. Cette étude a été conduite pour appréhender les effets de la macrofaune et des modes de gestion de la fertilité des sols sur l’évolution du carbone d’un lixisol en zone semi-aride du Burkina Faso. Pour ce faire, un dispositif expérimental en split-plot à trois répétitions comprenant deux traitements principaux (parcelles avec et sans macrofaune) et quatre modes de gestion de la fertilité, a été mis en place. Les résultats ont montré que la macrofaune, les modes de gestion de la fertilité et leur interaction n’ont pas eu d’effet significatif (P > 0,05) sur le carbone total et l’indice de gestion du carbone à court terme. Toutefois, la macrofaune a augmenté l’indice de gestion du carbone de 35 % ; elle a également augmenté la teneur en carbone des différentes fractions granulométriques. L’interaction entre la macrofaune et les modes de gestion de la fertilité a amélioré le rendement du niébé. L’intensification écologique des agrosystèmes par un usage raisonné des pesticides chimiques de synthèse et un apport de matière organique, pourraient améliorer à long terme, la séquestration du carbone.Mots clés : Biologie des sols, séquestration du carbone, pesticides, Burkina Faso

Effects of burning on soil macrofauna in a savanna-woodland under different experimental fuel load treatments

In West African savanna-woodland, the use of prescribed burning as a management tool has ecological implications for the soil biota. Yet, the effects of fire on soil inhabiting organisms are poorly understood. The aim of this study was to examine the responses of soil macro-invertebrates to early fires in a Sudanian savanna-woodland on a set of experimental plots subject to different fuel load treatments. The abundance of major macro-invertebrate taxa and functional groups, and taxon richness were quantified in soil cores collected from three different soil layers before and immediately after burning. The results indicated that, overall, there was substantial spatial and temporal variation in the composition of macro-invertebrate assemblages. The immediate effects of fire were to reduce total invertebrate numbers and numbers of many invertebrate groups dramatically. This is probably due to the fact that many of the surface-dwelling macrofauna perished as a result of less favorable microclimate due to fire, diminished resources, or migrate to safer environments. Fuel load treatment did not affect the community taxonomic richness or abundance of the soil-dwelling fauna. Furthermore, annual changes in community composition were more pronounced at the burnt site than in the control. This could be related to the inter-annual difference in precipitation pattern recorded during the two-year study period at our site. Since soil macrofauna population declines in fire-disturbed areas, increasing fire prevalence may jeopardize the long-term conservation of fire sensitive macrofauna groups. Special fire management attention is therefore recommended with due consideration to the type of burning and fuel properties to avoid the detrimental effects of intense fire affecting the resilience of savanna soil macrofauna species

Who are these youths? Language in the service of policy

In the 1990s policy relating to children and young people who offend developed as a result of the interplay of political imperatives and populist demands. The ‘responsibilisation’ of young offenders and the ‘no excuses’ culture of youth justice have been ‘marketed’ through a discourse which evidences linguistic changes. This article focuses on one particular area of policy change, that relating to the prosecutorial decision, to show how particular images of children were both reflected and constructed through a changing selection of words to describe the non-adult suspect and offender. In such minutiae of discourse can be found not only the signifiers of public attitudinal and policy change but also the means by which undesirable policy developments can be challenged

Young people, crime and school exclusion: a case of some surprises

During the 1990s the number of young people being permanently excluded from schools in England and Wales increased dramatically from 2,910 (1990/91) to a peak of 12,700 (1996/97). Coinciding with this rise was a resurgence of the debate centring on lawless and delinquent youth. With the publication of Young People and Crime (Graham and Bowling 1995) and Misspent Youth (Audit Commission 1996) the 'common sense assumption' that exclusion from school inexorably promoted crime received wide support, with the school excludee portrayed as another latter day 'folk devil'. This article explores the link between school exclusion and juvenile crime, and offers some key findings from a research study undertaken with 56 young people who had experience of being excluded from school. Self-report interview questions reveal that whilst 40 of the young people had offended, 90% (36) reported that the onset of their offending commenced prior to their first exclusion. Moreover, 50 (89.2% of the total number of young people in the sample), stated that they were no more likely to offend subsequent to being excluded and 31 (55.4%) stated that they were less likely to offend during their exclusion period. Often, this was because on being excluded, they were 'grounded' by their parents

Excavating youth justice reform: historical mapping and speculative prospects

This article analytically excavates youth justice reform (in England and Wales) by situating it in historical context, critically reviewing the competing rationales that underpin it and exploring the overarching social, economic, and political conditions within which it is framed. It advances an argument that the foundations of a recognisably modern youth justice system had been laid by the opening decade of the 20th Century and that youth justice reform in the post‐Second World War period has broadly been structured over four key phases. The core contention is that historical mapping facilitates an understanding of the unreconciled rationales and incoherent nature of youth justice reform to date, while also providing a speculative sense of future prospects