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This thesis was elaborated within the framework of the European Erasmus Mundus Programme “Agricultural Transformation by Innovation (AGTRAIN)”; L’objectif principal de cette thèse a été de rechercher une technique alternative de protection du niébé Vigna unguiculata (L.) contre le thrips des fleurs Megalurothrips sjostedti Trybom en se basant d’une part sur les pratiques actuelles des petits producteurs au Kenya et d’autre part sur le comportement et l’écologie de cette espèce à l’égard des signaux olfactifs qui seraient susceptibles de les repousser. Plus spécifiquement les buts à atteindre étaient les suivants: (1) Identifier et recenser les dégâts et l’impact sur la production occasionnés par les ravageurs du niébé dans différents agrosystèmes du Kenya et les méthodes utilisées par les petits producteurs pour les éviter ou les limiter; (2) Estimer l’impact des changements climatiques attendus dans les différentes régions d’Afrique sub-Saharienne sur la distribution du thrips des fleurs du niébé; (3) Etudier l’effet répulsif et insecticide de plusieurs huiles essentielles et de leurs composants majeurs sur les thrips pour proposer des associations avec des plantes potentiellement répulsives dans le cadre de stratégies de protection intégrées. L’idée de départ a été de recenser les pratiques des petits producteurs en matière de protection des cultures de niébé mais aussi identifier leur connaissance et leur perception des différentes techniques utilisées qui pourraient servir au développement d’une stratégie de protection intégrée en alternative à la lutte chimique. Afin de recenser le statut des différents ravageurs et d’identifier les pratiques de lutte utilisées, j’ai réalisé une enquête auprès des familles de petits producteurs, basée sur un questionnaire semi-structuré et ce dans plusieurs districts représentatifs de la région Est du Kenya principale zone de production du niébé. D’après les producteurs, les principaux ravageurs du niébé sont le thrips des fleurs M. sjostedti, le puceron Aphis craccivora et le foreur des gousses Maruca vitrata. La lutte chimique serait la principale, si ce n’est la seule, technique utilisée par les petits producteurs pour la protection du niébé avec une augmentation des fréquences d’application et des doses de pesticides chimiques utilisés en mélange qu’ils doivent pulvériser pour conserver leur efficacité. Ce résultat suggère la sélection de populations de ravageurs devenues résistantes aux pesticides qui ne peut qu’accentuer la baisse d’efficacité de cette lutte chimique sans parler de son impact croissant sur la santé et l’environnement. Ce problème viendrait s’ajouter, toujours aux dires des producteurs, à un régime pluviométrique irrégulier qui constitue avec les dégâts des ravageurs les principales contraintes de cette culture. Ces résultats nous ont permis de confirmer et compléter ceux de la littérature concernant en particulier les ravageurs et le niveau de connaissances des petits producteurs en matière de protection de la culture du niébé et de montrer la nécessité de développer des méthodes de lutte alternatives à la lutte chimique qui pourraient être adaptées aux conditions de cultures et adoptées par les producteurs. Nos résultats d’enquête ayant montré que les aléas climatiques étaient aussi un facteur important de perte de production pour 93% des producteurs, j’ai tenté d’estimer l’impact des changements climatiques potentiels en Afrique sub-Saharienne sur la distribution géographique du thrips M. sjostedti en me basant sur sa répartition actuelle (166 références) et la répartition du niébé (350 références). J’ai utilisé pour cela les outils MAXENT (Maximum Entropy) et AFRICLIM pour prédire les effets des changements climatiques en 2055. La pluviométrie et la température ont été les variables environnementales retenues en utilisant une méthode de ré-échantillonnage de type ‘jacknife’. J’ai aussi étudié l’effet répulsif et insecticide de 24 huiles essentielles et de leurs composés majeurs sur des adultes de thrips M. sjostedti en utilisant un olfactomètre à colonnes placées verticalement sous une hotte. Les résultats ont mis en évidence un fort effet répulsif de 7 extraits de plantes. J’ai effectué des analyses chimiques par hromatographie en phase gazeuse couplée à un spectrophotomètre de masse (GCMS) pour identifier les composés hydro-carbonés de ces 7 extraits. J’ai pu montrer l’effet répulsif mais pas insecticide de 16 de ces composés sur larves et adultes de M. sjostedti en utilisant différents bioessais. Les résultats de mes études ont montré le potentiel de l’utilisation d’extraits de plantes pour repousser les thrips. L’utilisation d’extraits de plantes répulsives pourrait être intégrée à une nouvelle stratégie de protection du niébé. Cependant aucun des composants testés n’a montré de propriété insecticide. Des plantes productrices de certains de ces composés volatiles répulsifs pourraient aussi être utilisées en association pour mieux protéger les cultures de niébé dans le cadre d’une stratégie de lutte intégrée de type push-pull. Mais ces plantes potentiellement répulsives devront avant tout être validés en laboratoire puis dans des expérimentations en plein champ.

Aim: To find an in vitro system for the measurement of the androgenic effects of different extracts of Hibiscus macranthus (Malvaceae) and Basella alba (Basellaceae). Methods: The production of testosterone from testes slices incubated in two media, either Krebs-Henseleit buffer containing 0.5 % Bovine serum albumin (BSA) or Dubecco’s Modified Eagle’s medium-F12 Ham nutrient mixture (DME/Ham F12), under a mixture of 5 % CO2 in 95 % air was determined either in the presence or absence of cofactors and Hibiscus macranthus plus Basella alba (HMBA) extracts. Results: The testosterone production was increased in testes slices incubated in DME/Ham F12 medium in response to the cofactors (49 %) and aqueous extracts (34 %–60 % according to dilutions). Under the same atmospheric conditions, there was no positive response of the testes slices to either cofactor or HMBA extract stimulation in Krebs-Henseleit buffer containing 0.5 % BSA. In further investigations related to the effect of HMBA, the DME/ Ham F12 medium was used. The results obtained from the in vitro test showed that the activity was present mainly in methylene chloride and methanol, since these extracts induced an increase in testosterone production by testes slices. Conclusion: The testes slice system is suitable to be used for further in vitro investigations of the isolation of androgenic bioactive components of plants. (Asian J Androl 2006 Jan; 8: 111–114)

We report the anti-Chagasic activity of the natural dihydrostilbenoid isonotholaenic acid and several simple derivatives, as well as that of some representative compounds of related synthetic series, with basic structures of benzalphthalides, dihydrostilbamides, isoindoles, phthalazin-1-ones, imidazo[2,1-a]isoindoles and pyrimido[2,1-a]isoindoles. The evaluation was performed in vitro on cultures of epimastigote and trypomastigote forms of Trypanosoma cruzi. Some of the tested compounds resulted to be as potent as benznidazole (epimastigotes), and others were shown to be more active than gentian violet (trypomastigotes), used as reference drugs.

International audience; In order to understand the action mechanism of non-antibiotic growth promoters on the growth performance of birds and to improve their use, the origin of individual variability response must be determined. For this purpose, the performance of chicken fed with or without plant extract blends were studied according to their growth potential estimated by their body weight at d10. A plant extract blend (EXVa) with an antimicrobial effect was used alone or preceded by another blend (EXVb) whose main effects were antioxidant and immunomodulator. Three experimental dietary treatments were performed (control, Exp1 and Exp2). In the control one, birds were fed on a diet with no growth promoter, in the Exp 1 the control diet was supplemented up to d22 with EXVa and in the Exp2, the control died was supplemented with EXVb from d0 to d10 and then with EXVaThis study was performed at two stocking densities, in 3m2 floor pens, either 12 birds/m² (normal density) or 17 birds/m² (high density). Body weight was recorded until broilers were 39 days old.Data were subjected to analysis of variance with two factors (dietary treatment, stocking density) and the body weight at d10 as co-variate. This analysis showing a significant effect on body weight at d10, three groups, with similar number, were defined according to d10 weight (Light, Medium, and Heavy). For each groups, growth data were subjected to analysis of variance with 2 factors (dietary treatment, stocking density). Significant differences between treatments were determined by Student-Newman-Keuls test (p≤0.05). Non significant differences showing biological differences were also specified (p

International audience; Catala-Gregori, P., Mallet, S., Travel, A., Orengo, J. and Lessire, M. 2008. Efficiency of a prebiotic and a plant extract alone or in combination on broiler performance and intestinal physiology. Can. J. Anim. Sci. 88: 623-629. A 36-d trial was conducted to evaluate two potential alternatives to antibiotic growth promoters in broilers. The products tested were a prebiotic (PROFEED (R)) and a plant extract (XTRACT (TM)). Ross mate broiler performance and digestive tract function responses were studied. To evaluate the effect of these potential alternatives alone or in combination, seven diets were tested: positive control avilamycin 10 ppm (PC);negative control antibiotic-free (NC); NC+PROFEED (R) 600 ppm (P); NC+XTRACT (TM) 100 ppm (X); NC+PROFEED (R)/XTRACT (TM) 600/100 ppm (XPH); NC+PROFEED (R)/XTRACT (TM) 450/75 ppm (XPM); NC+PROFEED (R)/XTRACT (TM) 300/50 ppm (XPL). From 22 to 36 d of age, body weight gain (BWG) was improved by P, X, and XPM compared with NC (P < 0.05). Throughout the trial, broilers fed PC, P, X and XPL had a better feed conversion ratio (FCR) than those fed NC (P < 0.1). No relevant negative effect was observed for the parameters relative to the digestive tract function:ileal histomorphometry, anaerobic sulphite-reducing bacteria count (ASR), intestinal and caecal pH, caecal volatile fatty acids production (VFA) and litter score (LS). With the higher mixture dose (XPH), no improvement in broiler performance was observed, suggesting no synergistic effect of the two additives.

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Pig weaning period is frequently associated with infectious disease, mainly caused by enterotoxigenic Escherichia coli (ETEC) K88. Plant extracts exert different beneficial effects and may represent antibiotic alternatives to reduce piglet infection. In this study, plant extracts and other natural substances (PENS) have been evaluated on the pig intestinal IPEC-1 cells, for potential protection against ETEC K88 induced membrane damage. Several PENS have been considered: yeast extract, yeast nucleotides, unsaturated oligo-mannuronic acid, ulvan, bromelain and three fractions of bovine colostrums, as anti-inflammatory and immunomodulatory compounds; daidzein and Chlorella vulgaris extract, as anti-oxidant compounds; allicin, cinnamaldehyde and carvacrol, as anti-bacterial compounds. First, possible toxic effect of PENS on cell membrane permeability was verified by assessing the transepithelial electrical resistance (TEER) and paracellular flux of the extracellular marker phenol red. The highest non-toxic PENS concentration was added to ETEC infected cells to test the protection against membrane damage. The results showed that yeast extract, daidzein, bovine colostrum, bromelain and allicin protected the cells against the increased membrane permeability caused by ETEC, whereas the other PENS did not show this ability. Allicin protection was not due to its anti-bacterial activity, since ETEC growth was unaffected by the presence of allicin.

Abstract An aqueous extract from leaves of Crotalaria virgulata subsp. grantiana was assayed for its effects on second-stage juveniles of Meloidogyne incognita. The biological activity was nematostatic; nematodes were not killed but were completely paralysed in a 1 mg/ml (w/v) extract: the LD50 equivalent was estimated to be 0.5 mg/ml. The effect was reversible: juveniles previously paralysed by C. grantiana extract recovered complete mobility in water and were able to infest a susceptible tomato plant. Freeze-dried aqueous extract from C. grantiana leaves added to a sterile sandy substrate at 1 mg/ml protected susceptible tomato plants from M. incognita infestation. This suggests a promising use of C. grantiana as both a green manure and natural alternative to synthetic chemicals in nematode population control, especially in integrated pest management for vegetable crops in organic agriculture of tropical and temperate areas.

The in vitro paralysis of second-stage juveniles of Meloidogyne incognita, M. javanica and M. mayaguensis by aqueous extracts of 15 West African Crotalaria species was analysed. A multivariate analysis distinguished four groups, based on their nematostatic activity: i) C. glaucoides extracts were not active; ii) the root extracts from C. goreensis, C. lathyroides and C. perrottetii were more active than the shoot extracts; iii) the shoot extracts from C. comosa and C. cylindrocarpa were more active than the root extracts; iv) both shoot and root extracts of C. atrorubens, C. barkae, C. grantiana, C. hyssopifolia, C. pallida, C. podocarpa, C. retusa, C. senegalensis and C. sphaerocarpa have nematostatic effects depending on either the Crotalaria species or plant tissue from which the extracts were derived. However, considering the greater biomass contribution of the leaves and stems compared to the roots when the plants are used as green manure, C. barkae, C. grantiana, C. pallida and C. podocarpa are the most efficient Crotalaria species, whatever the Meloidogyne species targeted.

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