De l'eau aux dattes : aperçu de la filière datte tunisienne et perspectives d'interventions

La modernisation et l'extension des aménagements hydrauliques dans les oasis du Sud tunisien renchérissent le coût de l'eau tout en accentuant la pression sur la ressource. Or ces oasis sont majoritairement orientées vers la production d'une variété de datte destinée principalement au marché international, la Deglet el Nour. La valorisation de l'eau par ces systèmes de production, et plus généralement, leur durabilité économique et écologique sont donc dépendantes du fonctionnement et des performances de la filière datte, particulièrement dans sa composante exportatrice. Partant des nombreuses études réalisées, complétées par un ensemble d'interviews réalisé dans le cadre du projet Sirma, cet article présente un aperçu de l'organisation et du fonctionnement de la filière. Celle-ci comprend 3 grands types d'acteurs : des producteurs nombreux, de petite taille et atomisés, des conditionneurs-exportateurs peu nombreux mais intégrant faiblement l'amont et l'aval, et des collecteurs jouant le rôle d'intermédiaires entre les précédents. La filière fonctionne essentiellement sous la forme d'un marché spot, sans réelle maîtrise des quantités et qualités livrées. Des stratégies d'investissement dans des capacités de stockage apparaissent néanmoins avec le décalage à venir entre la période de récolte (octobre à décembre) et le ramadan, pic de consommation. Quelques perspectives d'intervention sont tirées de ce premier diagnostic, replacées dans une problématique plus générale de supply chain management

Analysis of Tunisian date palm germplasm using simple sequence repeat primers

Inter Simple Sequence Repeat (ISSR) markers involve polymerase chain reaction (PCR) amplification of DNA using a single primer composed of a microsatellite sequence. ISSR technology rapidly reveals high polymorphic fingerprints and determines genetic diversity. We used genetic markers generated from selected ISSR primers to assess genetic diversity among a set of Tunisian date palm varieties. Seven primers were used to cluster 12 date palm varieties and 77 polymorphic markers were sufficient to identify all of the varieties. These discrete molecular markers were used to estimate genetic distances among the 12 accessions and to examine their genetic relationships. Data analysis identified phenetic groups that were in agreement with those obtained according to agronomic traits and random amplified polymorphic DNA (RAPD) markers. Among the 12 simple sequence repeat (SSR) motifs tested, the most abundant were AG. Key Words: Genetic diversity; ISSR polymorphisms; date palm; Pheonix dactylifera. African Journal of Biotechnology Vol. 3 (4), 2004: 215-21

Oral colistin sulfate in pigs: pharmacokinetics and effect on fecal Escherichia coli excretion of weaned pigs challenged with Escherichia coli F4 (K88)

Colistin sulfate (CS), a polymyxin antibiotic, is used in Canada for the treatment of post-weaning diarrhea in pigs as an alternative to neomycin. The aim of the present study was to evaluate some pharmcokinetics parameters of CS and its effect on the evolution of the intestinal Escherichia coli population in pigs challenged with enterotoxigenic E. coli (ETEC): F4

Impacts of colistin sulfate on fecal Escherichia coli resistance and on growth performance of piglets in a post-weaning diarrhea model

Colistin sulfate (CS) is used in Canada for the treatment of post weaning diarrhea (PWD), to overcome conventional therapeutic antibiotics failures. The aim of the present study was to determine the effect of a conventional oral regimen of CS for the treatment of PWD, on the development of E. coli CS resistance and to evaluate the effect of ETEC: F4 infection on CS intestinal absorption. A total of 48 pigs were used, challenge was carried out by oral administration of 109CFU of a hemolytic ETEC: F4 strain resistant to nalidixic acid. CS was administered at a dose of 50.000 UI/kg twice a day for 5 days. Feces were examined clinically and bacteriologically before and after challenge to evaluate presence of diarrhea and E. coli fecal excretion. ETEC: F4 virulence factors were monitored and CS plasma concentrations were quantified by an HPLC-MS/MS. From one until six days after CS administration, a significant reduction in the fecal excretion of ETEC: F4, total E. coli, ETEC: F4 virulence factors and in diarrhea scores was observed in the challenged treated group compared to the challenged untreated group (p\u3c0.0001). No significant difference in growth performances was observed in treated compared to non-treated pigs (p\u3e0.71). A significant selection pressure on E. coli total population was observed following CS treatment (p\u3c0.0001). Challenge with ETEC: F4 resulted in an increase in intestinal absorption of CS. Our study is the first to demonstrate in an experimental model of PWD, that CS at a dose of 50,000 IU/kg is effective in reducing fecal excretion of E. coli. However, this regimen was associated with a selection pressure on E. coli CS resistance, and did not improve growth performance in challenged pigs. Thus, the use of this antibiotic in pig should be revised

Efficacy of the Non-Pathogenic Agrobacterium Strains K84 and K1026 against Crown Gall in Tunisia

The non-pathogenic Agrobacterium radiobacter strain K84 and its genetically modified (GEM) strain K1026 were tested for their effectiveness against local Tunisian strains and two reference strains (C58 and B6) of the crown gall bacterium Agrobacterium tumefaciens. Tests in planta were carried out on herbaceous plants (tomato and tagetes) and on some sensitive rootstocks (bitter almond, peach almond hybrid GF677 and quince BA29). In vitro tests showed that both K84 and K1026 were effective and that the difference between these strains was not statistically significant. On tomato and tagetes, strain K84 was effective against all crown gall isolates with the exception of the A. tumefaciens reference strain B6. GEM strain K1026 was very effective against all isolates from Tunisia and against the reference strains. Both antagonistic strains significantly reduced the percentage of galled plants as well as the number of galls per plant. Under field conditions, both antagonists controlled crown gall effectively. Best results were obtained on the bitter almond-tree rootstock. Antagonist effectiveness was less evident on quince BA29 and peach almond GF677 rootstocks. The genetically modified strain K1026 is of interest in controlling crown gall disease in Tunisia

Liposarcoma of the extremities: MR imaging features and their correlation with pathologic data

SummaryObjectiveTo describe the MRI features of liposarcomas of the extremities and correlate them with data from the histologic subtypes.Material and methodsRetrospective study of 20 cases of liposarcoma of the extremities identified on MRI, surgically removed and confirmed at pathology. On MRI examination, T1- and T2-weighted fat-suppressed and non-fat-suppressed images were acquired then gadolinium-enhanced fat-suppressed T1-weighted images were obtained in at least two orthogonal planes.ResultsSixteen female and four male patients aged 12 to 77 years old at presentation, in 16 cases, with a slowly enlarging painless mass (demonstrating no associated local or general inflammatory components), located in the lower extremity (16 cases) and predominantly located in the thigh (13 cases). Pathologic examination revealed three cases of well-differentiated liposarcoma, 12 cases of myxoid liposarcoma one of which with round cells, three cases of pleomorphic liposarcoma, one case of dedifferentiated liposarcoma and one case of mixed-type liposarcoma. MR images mostly showed well-circumscribed tumors (19 cases) . Well-differentiated liposarcomas typically demonstrated a very specific diagnostic appearance as a predominantly adipose mass containing nonlipomatous components seen as thick septa that may show nodularity. Other subtypes of liposarcoma demonstrated a small amount of adipose tissue thus producing a marbled textural pattern on T1-weighted images particularly in myxoid liposarcomas (9 cases), or even nonlipomatous elements in high-grade liposarcomas (in round cell liposarcoma and in two out of three pleomorphic liposarcomas). The myxoid subtype has also a relatively characteristic appearance as a low signal intensity noted on T1-weighted images and a marked high signal intensity on T2. The dedifferentiated liposarcoma has a very specific radiologic appearance as a nonlipomatous component within a predominantly adipose mass, simulating that of well-differentiated liposarcomas.ConclusionMRI of extremity liposarcomas is a highly reliable and sensitive method to characterize liposarcomas. Besides its value in the diagnosis of liposarcoma and locoregional extension control, it allows proper identification of the specific histologic subtypes of liposarcoma.Level of evidenceLevel IV. Rétrospective diagnostic study

Bifurcation curves of subharmonic solutions

We revisit a problem considered by Chow and Hale on the existence of subharmonic solutions for perturbed systems. In the analytic setting, under more general (weaker) conditions, we prove their results on the existence of bifurcation curves from the nonexistence to the existence of subharmonic solutions. In particular our results apply also when one has degeneracy to first order -- i.e. when the subharmonic Melnikov function vanishes identically. Moreover we can deal as well with the case in which degeneracy persists to arbitrarily high orders, in the sense that suitable generalisations to higher orders of the subharmonic Melnikov function are also identically zero. In general the bifurcation curves are not analytic, and even when they are smooth they can form cusps at the origin: we say in this case that the curves are degenerate as the corresponding tangent lines coincide. The technique we use is completely different from that of Chow and Hale, and it is essentially based on rigorous perturbation theory.Comment: 29 pages, 2 figure