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  • 1
    ISSN: 1432-2242
    Keywords: Key words  Tef ; Eragrostis tef ; Genetic linkage map ; AFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A genetic linkage map of tef was constructed with amplified fragment length polymorphism (AFLP) markers using F5 recombinant inbred lines (RILs) derived by single seed descent from the intraspecific cross of ’Kaye Murri’×’Fesho’. A total of 192 EcoRI/MseI primer combinations were screened for parental polymorphism. Around three polymorphic fragments per primer combination were detected, indicating a low polymorphism level in tef. Fifty primer combinations were selected to assay the mapping population, and 226 loci segregated among 85 F5 RILs. Most AFLP loci behaved as dominant markers (presence or absence of a band), but about 15% of the loci were codominant. Significant deviations from the expected Mendelian segregation ratio were observed for 26 loci. The genetic linkage map comprised 211 markers assembled into 25 linkage groups and covered 2,149 cM of genome. AFLP is an efficient marker system for mapping plant species with low polymorphism such as tef. This is the first genetic linkage map constructed for tef. It will facilitate the mapping of genes controlling agronomically important traits and cultivar improvement in tef.
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  • 2
    ISSN: 1573-5060
    Keywords: Eragrostis curvula ; E. pilosa ; E. tef ; genetic diversity ; RAPD ; Tef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tef is one of the staple cereal crops in Ethiopia. To evaluate genetic diversity of tef and its relatives, 47 accessions of tef, three accessions of E. pilosa, and six accessions of E. curvulawere analyzed using random amplified polymorphic DNA (RAPD) markers. The level of polymorphism among the wild species was extremely high, while low polymorphism was detected among tef accessions. All cultivars and wild species under study could be distinguished with the help of different primers, thereby indicating the potential of RAPD in the genetic fingerprinting of tef. Accessions from E. curvula and E. pilosa can be differentiated by a single selected primer. In spite of low polymorphism within tef, accessions under study could be distinguished by a combination of selected primers. Cluster analysis indicated that tef is a very closely related species to E. pilosa with 45%similarity, supporting the hypothesis that tef originated from E. pilosa based on morphological data. Given that RAPD are relatively quick, simple to use, and are not subjected to environmental influences, they provide a valuable new approach for the genetic fingerprinting and study of genetic diversity in tef.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5060
    Keywords: epistasis ; Eragrostis tef ; generation means ; grain yield ; heritability ; t'ef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Quantitative genetics of grain yield and other agronomic characters of t'ef (Eragrostis tef) were studied using the F1, F2, BC1, and BC2 of the cross Fesho × Kay Murri. The study was carried out to estimate gene effects controlling the inheritance of grain yield and related agronomic characters. Significant additive [d] and dominance × dominance [l] interaction effects were detected for grain yield. The variations of yield per panicle and panicle weight were explained in terms of [d], dominance [h], and additive × additive [i] interactions. Non-allelic gene interactions were also detected for kernel weight, harvest index, tiller number, plant height, days to heading and days to maturity. The simple additive-dominance model explained the variation for panicle length, culm diameter and plant weight, allowing unbiased estimates of additive (D) and dominance (H) variance components. Large dominance variances (H) were estimated for grain yield, yield per panicle, and panicle weight. The additive variances for plant height, panicle length, days to heading and days to maturity were higher than the respective dominance variances. High narrow-sense heritability (h2) values (〉 0.50) were estimated for plant height, panicle length, days to heading and days to maturity. The lowest h2 (0.09) was obtained for kernel weight for which there was little variability. Since grain yield and several important agronomic characters of t'ef are influenced by non-allelic gene interaction, it is advisable to delay selection for yield to later generations with increased homozygosity.
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  • 4
    ISSN: 1573-5060
    Keywords: epistasis ; Eragrostis tef ; quantitative traits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The normal and selfed families of the triple test cross were employed to detect gene action in t'ef for grain yield and other useful agronomic characters in the breeding programme. Cultivars Kay Murri and Fesho were used as L1 and L2 testers, respectively. Eight randomly selected cultivars and two released varieties (DZ-01-354 and DZ-01-196) were crossed with the testers L1, L2 and L3 (the F1 of L1 × L2). In the case of the selfed families, 14 cultivars and two released varieties were used for crossing with the testers. The normal families were grown on an Inceptisol developed from volcanic ash whilst the selfed families were grown on a pellic Vertisol at the Debre Zeit Agricultural Research Centre, Ethiopia. The rainfall during the experimental season was 463 mm. Epistasis was detected for grain yield, yield per panicle, panicle weight, plant weight, harvest index, tiller number, panicle length, culm diameter, days to heading and days to maturity in the normal families of the triple test cross (TTC) of t'ef. Similarly the characters grain yield, yield per panicle, panicle weight, plant height, panicle length, days to heading and days to maturity showed epistasis in the selfed families of the TTC. Epistatic interaction was not important for shoot biomass and for harvest index (for the transformed data) in this family. Therefore, both the normal and selfed families of the TTC were in agreement with regard to detecting epistasis for grain yield, yield per panicle, panicle weight, panicle length, days to heading and days to maturity. Significant additive (D) and dominance (H) components were estimated for the characters in both families, although the magnitudes might have been inflated due to epistasis. The dominance component for panicle length was unimportant in both families of the TTC and as a result the additive components were not biased. In general, the additive, dominance and epistatic components were important in t'ef. Since the crop is self-fertilized only the additive and additive × additive terms are important to develop pure breeding varieties. Therefore, selection for superior segregants should start in advanced generations as homozygosity increases.
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  • 5
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Styrene was polymerized using different amounts of azoisobutyronitrile as initiator at temperatures of 70°C, 75°C and 80°C in suspension. The course of reaction up to almost complete conversion was modeled within a classical kinetic framework. Optimal simultaneous descriptions of both conversion and average degree of polymerization data were possible using two sets of values for the variation of the overall termination rate coefficient kt with conversion. One explanation for this is that kt is chain length dependent. Evidence for this necessity was derived by considering all kinetic parameters, except the termination rate coefficient, as reliable absolute values.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5044
    Keywords: Ergrostis ; spikelet culture ; t'ef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spikelets of t'ef, Eragrostis tef were cultured from the pre-anthesis stage to seed maturation, although only a small proportion of these seeds germinated to produce adult plants. A liquid culture medium originally formulated for wheat spikelets was used and it is of interest that grass stigmas normally classified as ‘dry’ function under these conditions. Varietal differences of response were observed and examples were found where although seed setting within the spikelet was less than under in vivo situation. The implications are considered for spikelet culture in an ‘old’ genus such as Eragrostis where one species, E. tef, is recognised as conspicuously variable.
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  • 7
    ISSN: 1573-5109
    Keywords: diversity ; Eragrostis tef ; germplasm ; tef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A total of 3600 entries of tef [Eragrostis tef (Zucc.) Trotter] germplasm collections representing 36 populations from six regions of Ethiopia were evaluated for phenotypic diversity in six qualitative and phenologic characters. High values of Shannon–Weaver diversity index ( $${H'}$$ ) were recorded for most characters in each population. Monomorphism was high for anther color (purple) and panicle form (loose). Larger variances for $${H'}$$ were obtained among regions than among populations within a region from hierarchical analysis of variance. Significant (P〈0.05) to highly significant (P〈0.01) t-values were observed among $${H'}$$ values of some regions for seed color, panicle form and days to maturity. A substantial level of variance (P〈0.05) was obtained for populations within altitudinal zones only for days to maturity. Altitudinal zones exhibited similar levels of diversity across characters for these collections. Generally, considerable variations important for tef improvement work have been observed and regions with highest diversity for some traits have been suggested for future in situ or ex situ germplasm conservation works. Although similar mean diversity indices were obtained among regions, they were non overlapping.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5060
    Keywords: clustering ; diversity ; Eragrostis tef ; genetic advance ; germplasm ; heritability ; principal components ; tef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three hundred twenty germplasm lines of the major Ethiopian cereal, tef, [ Eragrostis tef (Zucc.) Trotter], were evaluated for 20 morphological, phenological and agronomic characters in two-replicated randomized complete blocks at Debre Zeit and Melkassa Agricultural Research Centers in Ethiopia during the 1995 main season. The objectives were to assess the diversity of the lines, and to estimate the broad sense heritability (H) and genetic advance (GA) of the various characters. The mean squares of genotypes were highly significant (p ≤ 0.001) for all the traits. The phenotypic and genotypic coefficients of variation ranged in that order from about 6–40% and 3–23% for days to maturity and grain yield/plant, and days to maturity and number of spikelets/main shoot panicle, respectively. The cluster analysis grouped the genotypes into 14 major complexes consisting of one to 183 lines. Of the 19 principal components involved in explaining the entire variation among the genotypes the first five which had eigenvalues of more than one explained about 73.8%. The first principal component which accounted for about 34% of the total variance was due chiefly to plant height, culm and panicle length, diameters of the two basal culm internodes, main shoot panicle mass and grain yield, number of main shoot panicle branches and spikelets, and days to panicle emergence and maturity. Estimates of H varied from about 22% for length of the lowest main shoot stem internode to 74% for number of main shoot panicle branches. Values of GA (expected from selection of the superior 5% of the lines and expressed relative to the means) ranged from about 3% for days to maturity to 36% for number of spikelets/main shoot panicle. Overall, the study indicated the existence of trait diversity in tef germplasm and this can be exploited in the genetic improvement of the crop through hybridization and selection.
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  • 9
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eragrostis tef (Zucc) Trotter], is a major cereal crop in Ethiopia. The objective of this study was to investigate the genetic relationships among tef accessions by the amplified fragment length polymorphism (AFLP) technique. Forty-seven accessions of tef and one accession each of E. pilosa and E. curvula were analyzed. A total of 316 polymorphic DNA fragments across the three Eragrostis species were identified. The level of polymorphism within tef accessions was low (18%). However, with four or more primer pairs and a cluster analyses procedure, all the accessions included in the study were differentiated from each other. The three species studied fell in to three distinct clusters. Within tef, two major groups can be differentiated at 89% similarity. Because AFLP is reliable and enables assessment of potentially unlimited numbers of genetic loci, it permits greater insights into the genetic diversity of tef than had been possible with other available markers. Despite the low polymorphism level in tef, the availability of a large number of primer combinations and the high speed of the assay make AFLP an efficient marker technology for genetic diversity study of tef.
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  • 10
    Publication Date: 2018-06-02
    Description: Evaluation choreography - or who knows what when through the process of impact evaluation - has an important influence on the credibility and usefulness of findings. We explore such choreography from technical, political and ethical perspectives through reflection on a collaborative case study that entailed collaborative design of a qualitative impact evaluation protocol ('the QuIP') and its pilot use in Ethiopia and Malawi. Double blind interviewing was employed to reduce project specific confirmation bias, followed by staged 'unblinding' as a form of triangulation. We argue that these steps can enhance credibility of evidence and that ethical concerns associated with blinding can be addressed by being open with stakeholders about the process. The case study suggests qualitative impact evaluation can contribute to a more deliberative and less rigid style of international development practice.
    Keywords: ddc:330 ; Blinding ; confirmation bias ; impact evaluation ; international development practice ; qualitative methods
    Repository Name: EconStor: OA server of the German National Library of Economics - Leibniz Information Centre for Economics
    Language: English
    Type: doc-type:workingPaper
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