A study of Aerodynamic properties of Yam flour

The aerodynamic properties of five varieties of Yam namely: white yam, purple yam, three leaves yam, water yam and yellow yam were investigated under oven drying methods at 33oC. The dried yams were milled to flour and were taken to laboratory to determine their aerodynamic properties with respect to pneumatic conveying of the yam flours. The yam flour varieties recorded terminal velocity range of 1.38 to 1.60 m/s. Drag coefficient of 0.47 and Reynolds number varying from 0.63 to 0.97x10-5 kgm-2 /s. The analysis of variance conducted on the effect of yam varieties on the aerodynamic properties of yam flour did not show significant difference at both 5% and 1% level of probability. The study will guide engineers in design of yam flour pneumatic conveying equipment.

Environmental and economic impacts of pesticide treatment in the Yam Minisett Technique

White yam (Dioscorea rotundata) is an important tuber crop in a number of countries, but especially in West Africa where it serves as a food staple as well as a cash crop as excess production is sold in local markets. But the availability of quality planting material, most notably seed yams, for yam production remains an important constraint for farmers. Techniques have been developed to help address this limitation by cutting yam tubers into pieces (minisetts), treating them with the pesticide either via a seed dressing dust or pesticide ‘dips’ and planting to grow seed yams of the required size and quality. But while there have been many studies on the agronomy and adoption by farmers of these techniques, there have been fewer studies on their economic performance. Indeed, to date there have been no studies that compare the economic performance of treating setts compared to leaving them untreated, and neither has there been any analysis of the environmental impact of treating setts. This paper reports the results of a study designed to address these two gaps in knowledge and is based upon results from a series of farmer-managed seed yam plots established in the middle belt of Nigeria over 4 years (2013–2016). Results suggest that revenue and gross margin were higher for treated versus untreated setts although the latter still performed relatively well. Using the Field Use Environmental Impact Quotient (EIQ), the commonly recommended pesticide sett treatments were estimated to have a low-to-moderate environmental impact, and further research is needed to see how far pesticide use can be reduced to still be effective and minimise any environmental impact.

Functional properties of three native starches and their modified derivatives

Starches were isolated from cocoyam (Xanthosoma sagittifollium), white yam (Dioscorea rotundata) and bitter yam (Dioscorea dumentorum). Starch modification was carried out using acetic anhydride and phthalic anhydride. The native and modified starches were characterized using Fourier Transformed Infra-red Spectroscopy (FTIR) for identification of the functional groups. Functional properties such as water absorption capacities, oil absorption capacity, swelling power, solubility, gelation temperature, least gelation capacity, amylose content and pH were determined using standard procedures. Acetylation increased the water absorption capacity, oil absorption capacity, swelling power, amylose content, and solubility of the starches while phthalation decreased water absorption capacity, oil absorption capacity, swelling power, and solubility of the starches. Native cocoyam starch has the highest gelation temperature (85 °C) while Acetylated bitter yam has the lowest gelation temperature (74 °C). The pH of the native and modified starches was within the range of 4.14 − 6.55. Phthalation and acetylation increased the bulk density of the starches. Native cocoyam, white yam, and bitter yam starches had the lowest gelation concentration (6%). Modification of native starches will improve the usage of starch in food and non-food applications.

Genotyping-by-Sequencing to Unlock Genetic Diversity and Population Structure in White Yam (Dioscorea rotundata Poir.)

White yam (Dioscorearotundata Poir.) is one of the most important tuber crops in West Africa, where it is indigenous and represents the largest repository of biodiversity through several years of domestication, production, consumption, and trade. In this study, the genotyping-by-sequencing (GBS) approach was used to sequence 814 genotypes consisting of genebank landraces, breeding lines, and market varieties to understand the level of genetic diversity and pattern of the population structure among them. The genetic diversity among different genotypes was assessed using three complementary clustering methods, the model-based admixture, discriminant analysis of principal components (DAPC), and phylogenetic tree. ADMIXTURE analysis revealed an optimum number of four groups that matched with the number of clusters obtained through phylogenetic tree. Clustering results obtained from ADMIXTURE analysis were further validated using DAPC-based clustering. Analysis of molecular variance (AMOVA) revealed high genetic diversity (96%) within each genetic group. A network analysis was further carried out to depict the genetic relationships among the three genetic groups (breeding lines, genebank landraces, and market varieties) used in the study. This study showed that the use of advanced sequencing techniques such as GBS coupled with statistical analysis is a robust method for assessing genetic diversity and population structure in a complex crop such as white yam.

Multinomial Regression Analysis if Yam (Dioscorea Spp.) Consumers’ Preferences and Varietal Diversification Pattern in Nigeria

Multinomial regression analysis of yam consumers’ preference and varietal diversification in the yam production system in Nigeria was the thrust of this investigation. Five major yam farming communities were sampled randomly to get 200 respondents (suppliers and consumers) of yam. Parametric and non-parametric tests were employed to analyze the primary data collected with the questionnaire. The result indicates that white yam (Dioscorea rotundata) is the dominant variety among consuming households. The majority of the respondents prefer selling of white yam (76%) followed by water yam (13%) and yellow yam (l1%) in response to consumers’ preferences. The mean value of yam supplied was 505.34kg, while the mean quantity consumed was 14.56kg. The finding shows that the statistical relationship between the varieties consumed and supplied is strong and positive. It was concluded that as the demand-end is willing to purchase more quantity of white yam supplied, yam farmers and marketers are advised to scale-up production and supply respectively to take advantage of the increasing market demand for white yam in Nigeria. Also, more research works on yam varieties should be conducted by researchers to expand the value chain / industrial uses of other yam varieties to prevent their extinction.