Genetic diversity of the blast fungus, Magnaporthe grisea (Hebert) Barr, in Burkina Faso

Trapping nurseries trialed at two screening sites in Burkina Faso appeared to be an effective tool to characterize the virulence spectrum of blast populations using limited equipment and reduced labor. Itmade it possible to identify the best site to be used for screening for durable resistance. The effectiveness of some resistance genes indicated that they could be pyramided to provide durableresistance to blast fungus in Burkina Faso. The study also revealed the possible existence of new pathotypes in Burkina Faso. Fifty-five isolates of the blast fungus, Magnaporthe grisea, collected fromthe nurseries and rice fields were analyzed using random amplified polymorphic DNA (RAPD) PCR. Five major groups (Mg-1, Mg-2, Mg-3 Mg-4 and Mg-5) were defined. Mg-1, Mg-2 and Mg-3 were the largestgroups representing, 30.9, 25.5 and 30.9% of the 55 isolates analyzed. Only 9.1 and 3.6% belong to Mg-4 and Mg-5, respectively. Our results confirmed that RAPD PCR offers an inexpensive and speedy meansof generating markers for analyzing the population structure of the blast fungus

First report of Rice yellow mottle virus on rice in the Democratic Republic of Congo

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Earth blocks stabilized by cow-dung

WOS:000379589500010International audienceIn developing countries, most of the population cannot afford conventional building blocks made with the sand-cement mixture. In addition, these blocks do not provide thermal comfort and have a high embodied energy compared to vernacular materials. The main objective of this work was to produce low cost, resistant and durable (good resistance to water) blocks with a thermal behaviour enabling quality comfort indoor. For that purpose, the effects of cow-dung on microstructural changes in earth blocks (adobes) are investigated by means of X-ray diffraction, thermal gravimetric analyses, scanning electronic microscopy coupled with energy dispersive spectrometry, and video microscopy. The effects of these changes on the physical properties (water absorption and linear shrinkage) and mechanical properties (flexural and compressive strengths) of adobe blocks are evaluated. It is shown that cow-dung reacts with kaolinite and fine quartz to produce insoluble silicate amine, which glues the isolated soil particles together. Moreover, the significant presence of fibres in cow-dung prevents the propagation of cracks in the adobes and thus reinforces the material. The above phenomena make the adobe microstructure homogeneous with an apparent reduction of the porosity. The major effect of cow-dung additions is a significant improvement in the water resistance of adobe, which leads to the conclusion that adobes stabilized by cow-dung are suitable as building materials in wet climates

Exploiting Distance Technology to Foster Experimental Design as a Neglected Learning Objective in Labwork in Chemistry

This article deals with the design process of a remote laboratory for labwork in chemistry. In particular, it focuses on the mutual dependency of theoretical conjectures about learning in the experimental sciences and technological opportunities in creating learning environments. The design process involves a detailed analysis of the expert task and knowledge, e.g., spectrophotometry as a method for the determination of the concentration of a compound in a solution. In so doing, modifications in transposing tasks and knowledge to the learning situation can be monitored. The remote laboratory is described, as well as the specific features that alter the degree of fidelity of the learning situation in comparison to the expert one. It is conjectured that these alterations might represent actual benefits for learning

Physical, mechanical and hygrothermal properties of lateritic building stones (LBS) from Burkina Faso

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