Lessons from the field – Zimbabwe’s Conservation Agriculture Task Force

In the drier areas of southern Africa, farmers experience drought once every two to three years. Relief agencies have traditionally responded to the resulting famines by providing farmers with enough seed and inorganic fertilizer to enable them to re-establish their cropping enterprises. However, because of the lack of appropriate land and crop management interventions, vulnerable farmers are not necessarily able to translate these relief investments in seeds and fertilizer into sustained gains in productivity and incomes. A broad-based Task Force, led by the FAO (Food and Agriculture Organization of the United Nations) Emergency Office in Zimbabwe, is showing that relief and development are not mutually exclusive. Relief investments can be structured so as to yield both short- and long-term impacts. In 2004 the Task Force brainstormed a conservation farming strategy appropriate to the needs of vulnerable households with limited or no draft power. The strategy encompasses four major principles: (i) high management standard; (ii) minimum tillage – for instance, using planting basins which concentrate limited water and nutrient resources to the plant with limited labor input; (iii) the precision application of small doses of nitrogenbased fertilizer to achieve higher nutrient efficiency (from basal applications of organic and/or inorganic sources); and (iv) combining improved fertility with improved seed for higher productivity. These basic principles are taught and demonstrated to farmers who choose crop mixtures adapted to their local conditions and household resource constraints. This Precision Conservation Agriculture (PCA) spreads labor for land preparation over the dry seasons and encourages more timely planting, resulting in reduction of peak labor loads at planting, and higher productivity and incomes. Over the past three years, the PCA approach has been promoted by non-governmental organizations and national agricultural research and extension departments throughout Zimbabwe. It has consistently increased average cereal yields by 50 to 200% in more than 40,000 farm households (with the yield increase varying by rainfall regime, soil types and fertility, and market access). Rather than simply handing free seed and fertilizer inputs to farmers, teaching farmers PCA principles enables them to apply inputs (water, fertilizer and seed) more efficiently. The pursuit of input-use efficiency provides higher and more sustainable productivity gains needed to achieve better food security in drought-prone farming systems. The Task Force has generated (and quantified) substantial impacts in a short period; laid the foundation for sustainable development in a poor, drought-prone country; and provided lessons for future relief investment initiatives that will be valuable throughout sub-Saharan Africa

Overexpression of Hydroxynitrile Lyase in Cassava Roots Elevates Protein and Free Amino Acids while Reducing Residual Cyanogen Levels

Cassava is the major source of calories for more than 250 million Sub-Saharan Africans, however, it has the lowest protein-to-energy ratio of any major staple food crop in the world. A cassava-based diet provides less than 30% of the minimum daily requirement for protein. Moreover, both leaves and roots contain potentially toxic levels of cyanogenic glucosides. The major cyanogen in cassava is linamarin which is stored in the vacuole. Upon tissue disruption linamarin is deglycosylated by the apolplastic enzyme, linamarase, producing acetone cyanohydrin. Acetone cyanohydrin can spontaneously decompose at pHs >5.0 or temperatures >35°C, or is enzymatically broken down by hydroxynitrile lyase (HNL) to produce acetone and free cyanide which is then volatilized. Unlike leaves, cassava roots have little HNL activity. The lack of HNL activity in roots is associated with the accumulation of potentially toxic levels of acetone cyanohydrin in poorly processed roots. We hypothesized that the over-expression of HNL in cassava roots under the control of a root-specific, patatin promoter would not only accelerate cyanogenesis during food processing, resulting in a safer food product, but lead to increased root protein levels since HNL is sequestered in the cell wall. Transgenic lines expressing a patatin-driven HNL gene construct exhibited a 2–20 fold increase in relative HNL mRNA levels in roots when compared with wild type resulting in a threefold increase in total root protein in 7 month old plants. After food processing, HNL overexpressing lines had substantially reduced acetone cyanohydrin and cyanide levels in roots relative to wild-type roots. Furthermore, steady state linamarin levels in intact tissues were reduced by 80% in transgenic cassava roots. These results suggest that enhanced linamarin metabolism contributed to the elevated root protein levels

Cyanogenesis of Wild Lima Bean (Phaseolus lunatus L.) Is an Efficient Direct Defence in Nature

In natural systems plants face a plethora of antagonists and thus have evolved multiple defence strategies. Lima bean (Phaseolus lunatus L.) is a model plant for studies of inducible indirect anti-herbivore defences including the production of volatile organic compounds (VOCs) and extrafloral nectar (EFN). In contrast, studies on direct chemical defence mechanisms as crucial components of lima beans' defence syndrome under natural conditions are nonexistent. In this study, we focus on the cyanogenic potential (HCNp; concentration of cyanogenic glycosides) as a crucial parameter determining lima beans' cyanogenesis, i.e. the release of toxic hydrogen cyanide from preformed precursors. Quantitative variability of cyanogenesis in a natural population of wild lima bean in Mexico was significantly correlated with missing leaf area. Since existing correlations do not by necessity mean causal associations, the function of cyanogenesis as efficient plant defence was subsequently analysed in feeding trials. We used natural chrysomelid herbivores and clonal lima beans with known cyanogenic features produced from field-grown mother plants. We show that in addition to extensively investigated indirect defences, cyanogenesis has to be considered as an important direct defensive trait affecting lima beans' overall defence in nature. Our results indicate the general importance of analysing ‘multiple defence syndromes’ rather than single defence mechanisms in future functional analyses of plant defences

The elastic modulii of evaporated C60 films

Surface acoustic wave (SAW) pulses were excited in C60 films on a variety of substrates using pulses from Excimer lasers for excitation. An optical beam deflection technique and polymer electret transducers were utilized to detect the propagation of the SAW pulse with high spatial and temporal resolution, allowing an accuracy of better than 0.1% for SAW velocity measurements. With this technique the frequency dependence of the SAW velocity was determined for fullerite films and density, as well as elastic modulii of the films were derived by a theoretical analysis of the dispersion effect

Bilinear Discriminant Analysis for Face Recognition

International audienceIn this paper, we present a new statistical projection-based face recognition method, called Bilinear Discriminant Analysis (BDA). The proposed technique effectively combines two complementary versions of Two-Dimensional-Oriented Linear Discriminant Analysis (2DoLDA), namely Column-Oriented Linear Discriminant Analysis (CoLDA) and Row-Oriented Linear Discriminant Analysis (RoLDA). BDA relies on the maximization of a generalized bilinear projection-based Fisher criterion. A series of experiments was performed on various international face image databases in order to evaluate and compare the effectiveness of BDA to RoLDA and CoLDA. The experimental results indicate that BDA outperforms RoLDA, CoLDA and 2DPCA for face recognition, while leading to a significant dimensionality reduction

Oberflaechenmesstechnik mit Lasern. Duennschichtanalyse mittels lasergestuetzter Oberflaechenwellenspektroskopie (SAWS) Abschlussbericht

Available from TIB Hannover: F96B1717+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman