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Search Results: 1 - 10 of 26231 matches for " Martin Fregene "
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Mapeo genético y análisis de QTL para carotenos en una población s1 de yuca
Marín Colorado,Jaime Alberto; Ramírez,Hernando; Fregene,Martin;
Acta Agronómica , 2009,
Abstract: the s1 population of the thai variety mtai8 (am320), which shows patterns of segregation defined by the content of total carotenes (beta-carotene), underwent an analysis of segregating bulk (bsa = bulk segregating analysis) using 700 molecular markers type microsatellites or ssr. there were generated 25 tying groups and identifying 3 major qtls associated with a region of the genome of cassava with the content of total carotenes. three markers ssr; explained the 37.2% (ns109), 32% (rssry251) and 27.7% (rssry313) of the total phenotypic variance, placed in the group d strongly tying, associated with the content of total carotenes in the family am320 s1, which established a strong positive correlation between color and content root pulp carotenes total (r = 0.81), and between negative and carotenes total dry matter (r = -0.31). the three possible qtls showed positive and additive effect for the content of totals carotenes and could be an opportunity to implement assisted selection markers for total carotenes in cassava.
Yield traits as selection indices in seedling populations of cassava
Ojulong, Henry Fred;Labuschagne, Maryke Tine;Herselman, Liezel;Fregene, Martin;
Crop Breeding and Applied Biotechnology , 2010, DOI: 10.1590/S1984-70332010000300002
Abstract: the cassava breeding scheme currently used is long, because initial stages concentrate mainly on improving yield, with root quality selection following later. to shorten the scheme, yield and root quality should be selected simultaneously, starting at the seedling nursery. in this study, a nursery comprising of eight cassava families and 1885 seedlings developed from parents adapted to three major agro-ecologies, were evaluated for yield related traits in colombia. percentage dry matter content (dmc) and harvest index produced similar ranking of the parents. tuber yield, weight, and number showed potential of increasing yield through conventional breeding. a selection index including fresh root yield, percentage dmc, root weight and roots per plant, with heavier weights being assigned to root weight and roots per plant, should be used.
Diversidad y diferenciación genética de la yuca ( Manihot esculenta Crantz) con marcadores microsatélites en poblaciones de áfrica y Latinoamérica
Castelblanco Cepeda Wilson Hernando,Fregene Martin,Perea Dallos Margarita
Acta Biológica Colombiana , 2004,
Abstract: Se estudió la diversidad y diferenciación genética de 224 accesiones de yuca tradicionalmente cultivadas en Uganda. Adicionalmente, se incluyeron estudios previos de diversidad, 20 materiales de Tanzania, 20 de Ghana, 22 de Nigeria, 20 de Guatemala y 12 accesiones representando la colección núcleo de Latinoamérica, mantenidas en CIAT. Nueve grupos basados en el país de origen fueron creados para estudiar la variación genética dentro y entre países. Usando secuencias simples repetidas (SSR) o marcadores microsatélites, la variación en las frecuencias alélicas en 35 loci no ligados sirvió para estimar los parámetros de diversidad y diferenciación genética. Los resultados afirman una divergencia genética entre accesiones africanas y latinoamericanas, y una fuerte diferenciación de algunas accesiones de Guatemala con respecto a los otros países. Ellos también muestran una alta diversidad genética dentro de países y una moderada diferenciación entre ellos. En particular Uganda mantiene alta diversidad genética dentro Distritos aún después de una reciente epidemia de CMD (cassava mosaic disease) pero baja diferenciación entre ellos. Se discuten las posibles fuerzas implicadas en la dinámica de la diversidad genética, la importancia de Guatemala en los programas de mejoramiento de yuca en la búsqueda de grupos con potencial heterótico, el bajo impacto causado por CMD en la constitución genética del cultivo en Uganda y la observación de una distribución continua de la diversidad genética.
Mapeo genético y análisis de QTL para carotenos en una población s1 de yuca
Marín Colorado Jaime Alberto,Ramírez Hernando,Fregene Martin
Acta Agronómica , 2009,
Abstract: La población S1 de la variedad tailandesa de yuca MTAi8 (AM320), la cual presenta patrones de segregación definidos para el contenido de carotenos totales (Beta-caroteno), se sometió a un análisis de agrupamiento segregante (BSA = Bulk Segregant Analysis) empleando 700 marcadores moleculares tipo microsatélites o SSR. Se generaron 25 grupos de ligamiento identificando 3 QTL mayores asociados con una región del genoma de yuca con el contenido de carotenos totales. Tres marcadores SSR explicaron el 37.2% (NS109), 32% (rSSRY251) y 27.7% (rSSRY313) de la varianza fenotipica total, situados en el grupo de ligamiento D fuertemente asociados con el contenido de carotenos totales en la familia AM320 S1, se estableció una fuerte correlación positiva entre color de pulpa de raíz y contenido de carotenos totales (r=0.81), y negativa entre carotenos totales y materia seca (r= -0.31). Los tres posibles QTL presentaron efecto positivo y de carácter aditivo para el contenido de carotenos totales, pueden ser la oportunidad para implementar selección asistida por marcadores para carotenos totales en yuca.
Identificación de microsatélites en yuca asociados con la resistencia al ácaro Mononychellus tanajoa (Acari: Tetranychidae) Microsatellite identification associated with resistance to the mite Mononychellus tanajoa (Acari: Tetranychidae)
ELIANA DEL PILAR MACEA CHOPERENA,CESAR OSPINA,MARTIN FREGENE,JAMES MONTOYA-LERMA
Revista Colombiana de Entomología , 2012,
Abstract: El desarrollo del mapa genético de yuca ha facilitado las investigaciones en la búsqueda de genes asociados con resistencias a plagas que disminuyen producción y calidad. Las herramientas moleculares como los marcadores facilitan la identificación de los genes que dominan la resistencia a plagas como el caso del ácaro verde (AVY) Mononychellus tanajoa en yuca (Manihot esculenta). Inicialmente se identificaron los individuos de poblaciones retrocruces (BC1) progenie de las cuatro familias denominadas CW. De estos BC1 se seleccionaron individuos resistentes y susceptibles teniendo en cuenta la escala de da o reportada por el programa de Entomología del Centro Internacional de Agricultura Tropical. Se evaluaron 500 cebadores microsatélites mediante análisis de grupos segregantes (BSA), cinco de ellos expresaron polimorfismo y mostraron diferencias significativas entre los parentales, los grupos contrastantes y tres cebadores SSRY 11 SSRY 346 y NS 1099. Al realizar los análisis estadísticos correspondientes se encontró que los cebadores NS 1099 y NS 346 presentaron asociación entre estos y los individuos de las familias CW 67 CW 66 y CW 67 respectivamente. Las familias CW67 Y CW66 presentaron la mejor asociación con los marcadores y éstos presentaron mayor asociación con la característica de resistencia al da o causado por M. tanajoa en la población segregante (cebador NS1099 familias CW66 0.56 CW67 0.61 y NS346 familia CW67 0.61). Con base en estos resultados se puede sugerir la utilización de microsatélites en análisis posteriores en otras poblaciones para lograr la identificación de algunas regiones cromosómicas que confieren la resistencia al ácaro verde de la yuca. The development of the cassava genetic map has promoted research such as the finding of genes associated with the resistance of pests that diminish the production and quality of the crop. Molecular tools, such as markers can facilitate the identification of the genes that dominate resistance to pests this is the specific case of the presence of resistance to the green mite Mononychellus tanajoa (CGM) in cassava (Manihot esculenta). Initially, at International Center for Tropical Agriculture CIAT, individuals populations of backcrosses (BC1), lineage of four denominated families CW, were identified. These BC1 were identified and categorized according to 1-5 scale of damage reported by the Entomology Program at International Center for Tropical Agriculture. Resistant and susceptible individuals were identified. A total of 500 microsatellite markers were evaluated using the bulk segregant analy
Neural Stabilization/Excitation Control of a High-Order Power System by Adaptive Feedback Linearization
Kingsley Fregene,Diane Kennedy
Mathematics , 2000,
Abstract: This paper discusses the systematic design of an adaptive feedback linearizing neurocontroller for a high-order model of the synchronous machine/infinite bus power system. The power system is first modelled as an input-output nonlinear discrete-time system approximated by two neural networks. The approach allows a simple linear pole-placement controller (which is itself not a neural network) to be designed. The control law is specified such that the controller adaptively calculates an appropriate feedback linearizing control law at each sampling instant by utilizing plant parameter estimates provided by the neural system model. The control system also adapts itself on-line. This avoids the requirement for exact knowledge of the power system dynamics and full state measurement as well as other difficulties associated with implementing analytical input-output feedback linearizing control for a complex power system model. Furthermore, a departure is made from the `ad hoc' manner in which many neural controllers have been designed for power systems; the approach used here has foundations in control theoretic concepts of adaptive feedback linearization and pole-placement control design. Simulation results demonstrate the performance of this controller for a representative example of a single-machine/infinite bus power system configuration under various operational conditions.
Harmonizing the agricultural biotechnology debate for the benefit of African farmers
Segenet Kelemu, George Mahuku, Martin Fregene, Douglas Pachino, Nancy Johnson, Lee Calvert, Idupulapati Rao, Robin Buruchara, Tilahun Amede, Paul Kimani, Roger Kirkby, Susan Kaaria, Kwasi Ampofo
African Journal of Biotechnology , 2003,
Abstract: The intense debate over agricultural biotechnology is at once fascinating, confusing and disappointing. It is complicated by issues of ethical, moral, socio-economic, political, philosophical and scientific import. Its vocal champions exaggerate their claims of biotechnology as saviour of the poor and hungry, while, equally loudly, its opponents declare it as the doomsday devil of agriculture. Sandwiched between these two camps is the rest of the public, either absorbed or indifferent. Biotechnology issues specific to the African public must include crop and animal productivity, food security, alleviation of poverty and gender equity, and must exclude political considerations. Food and its availability are basic human rights issues—for people without food, everything else is insignificant. Although we should discuss and challenge new technologies and their products, bringing the agricultural biotechnology debate into food aid for Africa where millions are faced with life-or-death situations is irresponsible. Agricultural biotechnology promises the impoverished African a means to improve food security and reduce pressures on the environment, provided the perceived risks associated with the technology are addressed. This paper attempts to harmonize the debate, and to examine the potential benefits and risks that agricultural biotechnology brings to African farmers.
QTL analysis for early yield in a pseudo F2 population of cassava
E Okogbenin, J Marin, M Fregene
African Journal of Biotechnology , 2008,
Abstract: Genetic mapping of early bulking in a full-sib population of cassava was continued in a selfed family of 268 cassava plants derived from a single progeny of the full-sib population. The pseudo F2 population was analysed with 122 segregating SSR markers. A previously constructed linkage map of cassava consisting of 22 linkage groups covering 1236.7 cM, with an average marker distance of 18 cM was used for this study. The F2 population was evaluated for components of early yield, namely dry root yield (DR) at 7 months, harvest index (HI), and weight of fresh foliage (FF). Interval mapping, with single- and two-QTL models, was used to identify QTLs. The single-QTL model identified three QTLs each for DR, FF, and HI. The two-QTL model approach identified groups of QTLs that together explained 33% for FF, 43.5% for DR and 36% for HI. The identification of QTLs involved in early yield is an important step toward understanding quantitative genetic variation of early yield and implies reconsideration of breeding strategies for improvement of this complex trait.
Role of women in food security and seasonal variation of expenditure pattern in coastal fishing communities in Lagos State
TB Fregene, P.I Bolorunduro
Journal of Agricultural Extension , 2009,
Abstract: This study examined the socio-economic characteristics, role of women and expenditure pattern as it relates to seasonal variation in lagoon and marine fishing communities in Lagos State. A two stage stratified sampling method was used to select the sample size of 210 fishing (35 female and 175 male–headed) households from 25 lagoon and 10 marine fishing communities. Data were collected through field observation and administration of structured questionnaire at household level. Analytical technique used was descriptive statistics. Results indicate that though women do not fish in the high sea, female-headed households from among the Ilajes are actively involved in fishing in the lagoon waters. The study reveals that wives and daughters of fishermen are actively involved in fish processing, preservation and sales of fish caught as well as farming. Mean per Adult Equivalent Household Expenditure (MPAEHE) ranged from N350.74 for the first decile to N 3, 928.30 for the tenth decile. Percentage of the total expenditure spent on food decreased from 90.8% for the first decile to 41.9% in the tenth deciles. Other crucial roles of women in ensuring food security despite the seasonal variation are highlighted. The need to ensure food security should follow a multi-dimensional approach in order to achieve considerable improvement in the living standards of the poor fisher-folks.
Potential Impacts of Climate Change on Livelihood and Food Security of Artisanal Fisherfolks in Lagos State, Nigeria
Siyanbola Adewumi Omitoyin,Fregene Ben Tosan
Journal of Agricultural Science , 2012, DOI: 10.5539/jas.v4n9p20
Abstract: The artisanal fishery occupies a significant position in the Nigerian economy providing employment for about 5.8% of the Nigerian population and supplying 81.9% of the total domestic fish production. However, climate change is modifying the distribution of fish species with changes in habitat, size, species diversification and productivity. The study, therefore, examined the potential impact of climate change on livelihood and food security of artisanal fisherfolks in Lagos State, Nigeria A stratified sampling technique was used to select 88 fishing communities in Lagos State. A total of 311 respondents were interviewed using structured questionnaire. Data collected include socio-economic characteristics, livelihood parameters, fish species and productivity data while climatic data was obtained from the weather station and meteorology department. Data were analysed using descriptive statistics and stochastic frontier catch function analysis. The result of the analysis showed that there were changes in temperature and rainfall pattern which is a deviation from the normal trend. Variation in species diversity and abundance was also observed. There were other sources of livelihood engaged in either as primary or secondary occupation. There is the need to put in place strategies that will mitigate the effect of climate change
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