124 research outputs found

    Smallholder marketed surplus and input use under transactions costs: maize supply and fertilizer demand in Kenya

    Get PDF
    This paper assessed the effects of transactions costs—relative to price and non-price factors—on smallholder marketed surplus and input use in Kenya. A selectivity model was used that accounts not only for the effects of fixed and variable transactions costs but also for the role of assets, technology, and support services in promoting input use and generating a marketable surplus. Output supply and input demand responses to changes in transactions costs and price and non-price factors were estimated and decomposed into market entry and intensity. The results showed that while transactions costs indeed have significant negative effects on market participation, cost-mitigating innovations—such as group marketing—are also emerging to mitigate the costs of accessing markets. Output price has no effect on output market entry and only provides incentives for increased supply by sellers. On the other hand, both price and non-price factors have significant influence on adoption and intensity of input use. Overall, the findings suggest that policy options are available other than price policies to promote input use and agricultural surplus.Commercialization, Marketed surplus, Fertilizer use, Transactions cost, Kenya, Agricultural and Food Policy, Agricultural Finance, Consumer/Household Economics, Environmental Economics and Policy, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Institutional and Behavioral Economics, International Relations/Trade, Marketing, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies, Research Methods/ Statistical Methods,

    Harnessing modern biotechnology for tropical tuber crop improvement: Yam (Dioscorea spp.) molecular breeding

    Get PDF
    Yams (Dioscorea spp.) constitute a staple food crop for over 100 million people in the humid and subhumid tropics. They are polyploid and vegetatively propagated. The Guinea yams, Dioscorea rotundata and D. cayenensis, are the most important yams in West and Central Africa where they are indigenous, while D. alata (referred to as water yam) is the most widely distributed species globally. The genetics of yams is least understood among the major staple food crops due to several biological constraints and research neglect. Research to unravel the apparent complexity of the yam genome will have far-reaching implications for genetic improvement of this important tuber crop. Some progress has been made in recent years in germplasm characterization and the development of molecular markers for genome analysis. A genetic linkage map based on amplified fragment length polymorphism (AFLP) markers has been constructed for Guinea and water yams. These linkage maps were used to scan the genome for quantitative trait loci (QTL) associated with genes conferring resistance to Yam Mosaic Virus (YMV) in D. rotundata and anthracnose (Colletotrichum gloeosporioides) in D. alata. In addition, candidate random amplified polymorphic DNA (RAPD) markers associated with major genes controlling resistance to YMV and anthracnose have been identified that could be used for selection and pyramiding of YMV and anthracnose resistance genes in yam improvement. Also, molecular markers such as RAPDs, AFLPs, and microsatellites or simple sequence repeats (SSRs) have been developed for yam genome analysis. An initial c-DNA library has been constructed in order to develop expressed sequence tags (ESTs) for gene discovery and as a source of additional molecular markers. This paper will review the advances made, discuss the implications for yam genetic improvement and germplasm conservation, and outline the direction for future research. Key words: Genetic mapping, genome analysis, molecular breeding, PCR-based markers, QTLs, resistance genes, yam. African Journal of Biotechnology Vol. 2 (12), pp. 478-485, December 200

    Livelihood Strategies of Resource-Poor Farmers in Striga-Infested Areas of Western Kenya.

    Get PDF
    Striga hermonthica (del) Benth is threatening rural livelihoods in western Kenya where maize is the major food and cash crop. Vulnerability analysis was conducted on a sample of 802 households in eight districts of Nyanza and Western provinces. Farmers perceived Striga as the major cause of poverty and food insecurity. Both household income and child nutrition indicators showed alarming conditions for the majority of households. The coping strategies and informal safety nets were not capable of addressing the vulnerability issue successfully. A logistic regression model of determinants of poverty was estimated to examine the determinants and correlates of poverty. Results revealed certain characteristics of households that were more likely to be poor: poor access to land and farm assets; high dependency ratio; headed by older farmer with low education attainment; no off-farm work, no cash crops; depend on credit; Striga has been on the farm for long, high perceived yield loss to Striga given high dependency on maize for livelihoods; adopt no integrated Striga control options; and live in Bondo and Vihiga districts. The paper concludes with implications for policy to improve the livelihoods of small-scale farmers in the Striga-affected areas of western Kenya. Key words: livelihoods, maize, Striga, Kenya, Logitlivelihoods, maize, Kenya, Striga, logit, Agricultural and Food Policy, Community/Rural/Urban Development, Consumer/Household Economics, Environmental Economics and Policy, Farm Management, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Health Economics and Policy, Land Economics/Use, Marketing, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies,

    Seed yam production from whole tubers versus minisetts

    Get PDF
    Open Access Article; Published online: 22 June 2020Yam (Dioscorea rotundata Poir.) is a major staple and cash crop for millions of households in West Africa, where about 93% of the world crop is produced. The tuber serves as food and seed. Depending on the size, seed tubers are often cut into setts, minisetts, or planted whole. An experiment was conducted to investigate the effects of using whole tubers versus minisetts to produce seed yams. Six treatments constituted combinations of whole tubers and minisetts, and three tuber-size classes, viz., 30–59 g, 60–89 g, and 90–120 g (averaged and referred to as 45 g, 75 g, and 105 g, respectively). The experiment was conducted as a randomized complete block design with three replications. Results showed that plants from whole tubers emerged from the soil faster and yielded 48% more than those from minisetts. The mean yield of 105 g minisetts (18.3 t/ha) was statistically similar to that of 45 g whole seed (17.9 t/ha). Using 45 g whole seed would save about 2 t/ha of the harvested crop for use as food instead of seed. So, planting small whole tubers is more profitable than minisetts and is recommended to yam growers

    A Standardized RNA Isolation Protocol for Yam (Dioscorea alata L) cDNA Library Construction

    Get PDF
    For the purpose of constructing yam cDNA libraries, attempts to isolate high quality RNA using several previously reported protocols were unsuccessful. Therefore a protocol was standardized for yam total RNA isolation by using guanidium buffer at the Department of Biology, Virginia State University. The RNA isolated using this standardized protocol was high in quality and led to successful good quality cDNA library construction and identification of functional ESTs in yam

    Molecular taxonomic, epidemiological and population genetic approaches to understanding yam anthracnose disease

    Get PDF
    Water yam (Dioscorea alata L.) is the most widely cultivated yam species globally. The major limitation to the profitable and sustainable production of D. alata is its susceptibility to anthracnose disease. The availability of resistant varieties could potentially form the cornerstone of an integrated management strategy for yam anthracnose; however, anthracnose resistance breeding is hampered by the dearth of knowledge on pathogen identity and diversity. Four forms of Colletotrichum are now known to be associated with foliar anthracnose of yam: the slow-growing grey (SGG), the fast-growing salmon (FGS), the fast-growing olive (FGO), and the fast-growing grey (FGG) forms. The close phylogenetic relationship of the first three forms to reference isolates of Colletotrichum gloeosporioides, and the fact that only strains of these forms have been observed to induce typical anthracnose symptoms on D. alata, recently confirmed that C. gloeosporioides is the causal agent of yam anthracnose disease. The FGG form possibly represents a distinct, endophytic, species as indicated by morphological, biological and molecular criteria. Previous research emphasized epidemiology and control but limited progress was made in understanding yam anthracnose disease based on this classical approach. Molecular approaches have started to unravel the systematics and ecology of Colletotrichum strains associated with yam anthracnose, as well the population biology of C. gloeosporioides on yam. Sexual recombination is a likely mechanism contributing to the high genetic diversity of C. gloeosporioides in yam-based cropping systems. Studies have been initiated to understand the mechanisms that generate genetic variation in C. gloeosporioides, and to gain some insight into the biochemistry of the interactions between the pathogen and yam. Our thesis in this article is that integrating traditional and molecular approaches to understanding C. gloeosporioides systematics, epidemiology and population genetics will lead to a much better understanding of yam anthracnose disease, and thus to the development of effective and sustainable control measures. Research successes and challenges are discussed, as well as their implications for future studies on pathogen evolutionary potential, anthracnose resistance breeding, and the deployment of resistance genes. Key words: Anthracnose, Colletotrichum gloeosporioides, Dioscorea spp., molecular markers, molecular systematics, population biology, resistance breeding, yam. African Journal of Biotechnology Vol. 2 (12), pp. 486-496, December 200

    Diversity of banana streak-inducing viruses in Nigeria and Ghana: Twice as many sources detected by immunoelectron microscopy (IEM) than by TAS-ELISA or IC-PCR

    Get PDF
    Our previous study had shown that some Musa leaf samples with Banana streak symptoms tested negative for Banana streak virus (BSV) in triple antibody-sandwich ELISA (TAS-ELISA). Therefore, in this study 63 additional Musa leaf samples were tested for BSV by TAS-ELISA, immunoelectron microscopy (IEM) and immunocapture polymerase chain reaction (IC-PCR). Sensitivity tests by sap dilution end-point analyses indicated that IC-PCR was considerably more sensitive than IEM fordetecting typical BSV, while IEM proved to be of similar sensitivity as TAS-ELISA. However, when leaf samples of Musa plants, obtained from different farmers’ fields in Nigeria and Ghana and some Nigeriansources maintained in the greenhouse were screened for BSV, more than twice as many samples revealed BSV-like particles by IEM than were detected by TAS-ELISA or IC-PCR. Of the 51 leaf samplesthat were BSV positive in all tests taken together, 48 were positive by IEM, 25 by IC-PCR and only 19 by TAS-ELISA. Upon IEM examination, typical bacilliform BSV-like particles were clearly recognized although in very diverse concentrations. Bacilliform particles deviating in length from the main particle populations or showing an angularly bent morphology were found. Occasionally, in certain samples and with certain antisera the IEM decoration tests revealed mixtures of strongly decorated and weaklydecorated BSV-like particles or bacilliform particles which did not at all react with the antibodies available. This proved, the occurrence, besides the presence of typical BSV, of diverse populations of BSV-like viruses in West Afric
    • …