A manual for large-scale sample collection, preservation, tracking, DNA extraction, and variety identification analysis

Several alternative options have been used for varietal identification. However most of the traditional methods have inherent uncertainty levels and estimates often have wide confidence intervals. In an attempt to circumvent traditional survey-based measurement errors in varietal identification, DNA-based varietal identification has been implemented in the Cassava Monitoring Survey (CMS) of Nigeria — a large adoption study involving 2500 cassava farming households. The DNA fingerprinting technique offers a reliable method to accurately identify varieties grown by farmers and increases accuracy and credibility in the interpretation of adoption rates and associated economic and policy analyses. Unlike phenotype-based methods, DNA is not affected by environmental conditions or plant growth stage and is more abundant than morphological descriptors. However, undertaking a credible DNA-based varietal identification is not a trivial matter because of the logistical challenges involving sample collection and tracking by a large team of field enumerators. This manual presents the detailed steps required for undertaking reliable DNA-fingerprinting-based identification of cassava varieties. In particular, the manual gives detailed information on the establishment of a sample tracking system, preparation of a readily available and cheap sample collection kit, field sample collection methodology, preparation of samples for DNA isolation, and development of a pipeline for variety identification analysis. This manual is part of the outputs of the CMS project funded by the CGIAR Research Program on Roots, Tubers and Bananas (RTB), the Bill & Melinda Gates Foundation, and the International Institute of Tropical Agriculture (IITA)

Cassava farmers' preferences for varieties and seed dissemination system in Nigeria: gender and regional perspectives

The Cassava Monitoring Survey (CMS) project was funded by the CGIAR-RTB Program and the Bill & Melinda Gates Foundation. The main goal was to carry out a study on cassava adoption and diffusion patterns in Nigeria. This includes explaining why farmers are adopting certain varieties and describing preference differences across regions and gender. This specific study and report is part of Component IV of the broader CMS Project, and it covered gender-differentiated, end-user surveys on varietal and trait preferences. The objective of this component was to use qualitative methods to probe deeper into some of the information that was obtained in the quantitative survey on gender-based trait preferences and seed dissemination pathways

Can smallholder farmers adapt to climate variability, and how effective are policy interventions? Agent-based simulation results for Ethiopia

Climate variability with unexpected droughts and floods causes serious production losses and worsens food security, especially in Sub-Saharan Africa. This study applies stochastic bioeconomic modeling to analyze smallholder adaptation to climate and price variability in Ethiopia. It uses the agent-based simulation package Mathematical Programming-based Multi-Agent Systems (MPMAS) to capture nonseparable production and consumption decisions at household level, considering livestock and eucalyptus sales for consumption smoothing, as well as farmer responses to policy interventions. We find the promotion of new maize and wheat varieties to be an effective adaptation option, on average, especially when accompanied by policy interventions such as credit and fertilizer subsidy. We also find that the effectiveness of available adaptation options is quite different across the heterogeneous smallholder population in Ethiopia. This implies that policy assessments based on average farm households may mislead policy makers to adhere to interventions that are beneficial on average albeit ineffective in addressing the particular needs of poor and food insecure farmers

Ammonia gas sensing characteristics of V2O5 nanostructures: A combined experimental and ab initio density functional theory approach

A combined experimental and density functional theory of α-V2O5 for ammonia gas sensing have been investigated. The material was synthesized from hydrated NH4VO3 in CVD at 400 °C in N2 atmosphere for different time (12 h and 24 h). Highly crystalline orthorhombic α-V2O5 nano-rods with dominant (001) and (110) planes/facets nano-rods were observed from XRD, SEM and TEM characterizations. Using VSM technique, para-to ferro-magnetic transition was observed in the α-V2O5 nanoparticles synthesized at 24 h. Improved gas sensing was observed in case of the paramagnetic α-V2O5 nano-rods (nanoparticles synthesized at 12 h) compared with the one synthesized at 24 h. Additionally, significant rise in gas sensing response was observed around the metal to insulator transition temperature. Calculation of adsorption of NH3 molecule(s) on (001), (110), (200) and (400) facets showed that (001), (200) and (400) possessed more active sites than (110) surface. However, at higher concentration of NH3 molecules, the number of adsorbed molecules was found to be limited by the available adsorption sites in the case of (001) thereby causing the surface to be unstable. DFT calculations were also used to investigate NH3 adsorption on (110) surface of α-V2O5 with the analysis showing exponential decrease in the electronic band gap of the material's surface with the increasing numbers of NH3 loadings.</p