Development and diffusion of integrated Striga control practices for small-scale farmers in western Kenya

The parasitic weed Striga hermonthica has become one of the most significant constraints to cereal production in western Kenya. In 1995 a collaborative project was initiated to develop control technologies for Kenyan farmers

Identification of Genes Contributing to the Virulence of Francisella tularensis SCHU S4 in a Mouse Intradermal Infection Model

Background: Francisella tularensis is a highly virulent human pathogen. The most virulent strains belong to subspecies tularensis and these strains cause a sometimes fatal disease. Despite an intense recent research effort, there is very limited information available that explains the unique features of subspecies tularensis strains that distinguish them from other F. tularensis strains and that explain their high virulence. Here we report the use of targeted mutagenesis to investigate the roles of various genes or pathways for the virulence of strain SCHU S4, the type strain of subspecies tularensis. Methodology/Principal Findings: The virulence of SCHU S4 mutants was assessed by following the outcome of infection after intradermal administration of graded doses of bacteria. By this route, the LD\u2085\u2080 of the SCHU S4 strain is one CFU. The virulence of 20 in-frame deletion mutants and 37 transposon mutants was assessed. A majority of the mutants did not show increased prolonged time to death, among them notably \u394pyrB and \u394recA. Of the remaining, mutations in six unique targets, tolC, rep, FTT0609, FTT1149c, ahpC, and hfq resulted in significantly prolonged time to death and mutations in nine targets, rplA, wbtI, iglB, iglD, purL, purF, ggt, kdtA, and glpX, led to marked attenuation with an LD\u2085\u2080 of >10\ub3 CFU. In fact, the latter seven mutants showed very marked attenuation with an LD\u2085\u2080 of 6510\u2077 CFU. Conclusions/Significance: The results demonstrate that the characterization of targeted mutants yielded important information about essential virulence determinants that will help to identify the so far little understood extreme virulence of F. tularensis subspecies tularensis.Peer reviewed: YesNRC publication: Ye

Improving the value of maize as livestock feed to enhance the livelihoods of maize-livestock farmers in East Africa

Presentation by D. Friesen (CIMMYT) to the CGIAR Systemwide Livestock Programme Livestock Policy Group Meeting, 1 December 2009Presentation by D. Friesen (CIMMYT) to the CGIAR Systemwide Livestock Programme Livestock Policy Group Meeting, 1 December 200

Liming and lime-phosphorus-zinc interactions in two Nigerian Ultisols: I. Interactions in the soil

Interactions of lime, phosphorus (P), and zinc (Zn) in two coarse-textured Ultisols from southeastern Nigeria were examined by means of factorial soil incubation and phosphate sorption experiments. In both soils, liming reduced exchangeable aluminum (Al) saturation from 45% to < 5% at pH 5.0 and soil solution Al concentration to < 1.0 µg/ml also near pH 5.0. There was no significant lime-P interaction on active Al levels, indicating a lack of any ameliorating value of P on Al toxicity. Adsorption isotherms showed that liming reduced P adsorption in both soils at equilibrium solution concentrations of approximately 0.2 µg P/ml or higher, but at lower concentrations the effect became inconsistent. Soil incubation studies indicated that the concentration of P in soil solution (null-point estimate) was first reduced by lower rates of lime then increased when soils were limed to approximately pH 6.0 or higher. Zinc activity in soil solution declined sharply when soils were limed to pH above 5.0, but was unaffected by P applications within the pH range studied (pH 4.3 to 7.2)