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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 38 (1982), S. 13-18 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Weed research 45 (2005), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The parasitic angiosperms, Striga hermonthica and Striga asiatica, severely constrain cereal production in sub-Saharan Africa by causing huge losses in grain yield. Understanding the diversity of Striga populations is important because it allows identification of races or biotypes thus improving chances of breeding success. Amplified fragment length polymorphism (AFLP) analysis was used to study genetic diversity among 17 populations of S. asiatica and 24 populations of S. hermonthica from Kenya. A total of 349 DNA fragments ranging from 51 to 500 bp were obtained from four EcoRI and MseI primer combinations. Genetic distances for S. asiatica populations ranged from 0.009 to 0.116 with a mean of 0.032. S. hermonthica populations had a genetic distance that ranged from 0.007 to 0.025 with a mean of 0.015. Only two clusters were found in S. asiatica populations whereas no apparent structure was evident in S. hermonthica populations. There was no evidence of isolation by distance for the two species. Although the low genetic diversity suggests Striga is relatively uniform across the populations studied, it is possible that pathogenicity and virulence genes may be located in genomic regions that were not sampled. The data, however, does not provide evidence to support diversification of both Striga species in the region where the study was conducted.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Arachis hypogaea L.), an important agronomic crop, exhibits a considerable amount of variability for morphological traits and for resistance to diseases and pests. In contrast, molecular marker assays have detected little variation at the nucleic acid level. Identification of molecular markers would be of great help to peanut breeders, geneticists, and taxonomists. The objectives of this work were to identify simple sequence repeat (SSR) markers in cultivated peanut and to test these markers for their ability to discriminate among accessions. Peanut total genomic DNA libraries were constructed and screened with 32P-labeled dinucleotide repeats, (GT)10 and (CT)10. DNA sequences were obtained from the SSR-containing clones and, when possible, primer pairs were designed on the basis of DNA sequences flanking the repeat motif. Primer pairs were tested in polymerase chain reaction (PCR) assays using a collection of 22 peanut DNAs, representing both cultivated peanut and wild species. In all, six SSR markers, five from the library screening procedure and one additional marker obtained from a search of publicly available DNA sequences, detected polymorphisms among the peanut DNAs. Discrimination power was high among the cultivated peanuts, with 17 unique genotypes represented among the 19 accessions tested. From two to 14 DNA fragments were amplified per SSR marker, and as a group, the six markers may amplify up to 10 putive SSR loci. The SSR markers identified in this study were more effective in detecting molecular variation in cultivated peanut than all other DNA-based marker evaluated to date.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Sorghum bicolor (L.) Moench] inbreds were used to compare the discrimination abilities of 15 SSR primers with 104 RFLPs and to compare the associations among lines revealed by these molecular data and by pedigrees. RFLP data allowed all lines to be uniquely identified; two lines could not be distinguished by the SSR data. The mean polymorphism information content (PIC) values were 0.62 (RFLPs) and 0.58 (SSRs). Correlations for pairwise molecular profile distances with pedigree distances among the maintainer female (B) lines were 0.52 and 0.53 for RFLP and SSR data, respectively; data for the male parental restorer (R) lines were 0.41 and 0.47. This set of SSRs could be used to help genetic conservation management and to support IPP. Data from additional SSRs that collectively cover more of the genome will be required for applications to assist in breeding.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Sorghum bicolor (L.) Moench] accessions identified as 'Orange' presently maintained by the U.S. National Plant Germplasm system (NPGS) were assayed with 15 simple sequence repeat (SSR) markers. Genotyping was performed with fluorescent primers with five primer sets in each of three multiplex polymerase chain reactions (PCRs) and automated allele sizing. A total of 96 individuals were analyzed, five plants from each of 19 Orange accessions and one individual from an elite inbred line, 'RTx430'. The SSR markers provided substantial genetic resolution among the Orange entries. Average heterozygosity estimates were low, and phenetic analyses (neighbor-joining dendograms) were generally consistent with known historical relationships among accessions. Most accessions were genetically distinct, but two redundant groups (involving a total of five entries) were found among the 19 Orange accessions evaluated. The molecular variance analysis (AMOVA) showed that 90% of the total genetic variation was partitioned among accessions, while one-tenth of the variation resulted from genetic differences between individual plants within accessions. The variance analysis also indicated that it should be possible to reduce the number of Orange accessions held by NPGS by almost half without seriously jeopardizing the overall amount of genetic variation contained in these holdings. This study demonstrated that a limited number of SSR markers can be used in a cost-efficient manner to rapidly assess variation in accessions of Orange sorghum.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2242
    Keywords: Key words AMOVA ; Conservation ; Curation ; Genetic markers ; Molecular genetic screening ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To better characterize and conserve crop genetic resources, the assessment of genetic identity, relatedness, and structure among entries and collections becomes a priority. In the present study, a random amplified polymorphic DNA (RAPD) assay was applied as a quick, cost-effective, and preliminary screen to quantify and partition the molecular variation among accessions. Fourteen phenotypically uniform accessions of Brassica oleracea var. capitata L. (cabbage) similarly designated as `Golden Acre' were tested with nine decamer oligonucleotide primers. These amplifications generated 110 fragments, of which 80 were polymorphic ranging in size from 370 to 1720 bp. The 80 polymorphic fragments were sufficient to distinguish between all 14 accessions. Data based on the partitioning of variation among accessions indicated that `Golden Acre' entries could be reduced to as few as four groups, with the potential loss of variation being only 4.6% of the absolute current genetic variation in those holdings as estimated from RAPD analysis. This proposed grouping would concurrently save approximately 70% [$750–1000 (US) per accession] for each cycle of regeneration (approximately 20–25 years at most) which alternatively could then be used for other priorities in B. oleracea conservation and use. This case represents but one example where targeted use of a molecular-marker assay linked with rigorous statistical analysis will be useful for plant genebank management, particularly for questions at the intraspecific level. Molecular markers will provide genebank curators with additional sources of information to better plan and organize collection holdings and use finite financial support in a more effective manner.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2242
    Keywords: Microsatellite ; Germplasm ; Genetic resources ; Genetic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Simple sequence repeats (SSRs), also known as microsatellites, are highly variable DNA sequences that can be used as markers for the genetic analysis of plants. Three approaches were followed for the development of PCR primers for the amplification of DNA fragments containing SSRs from sorghum [Sorghum bicolor (L.) Moench]: a search for sorghum SSRs in public DNA databases; the use of SSR-specific primers developed in the Poaceae species maize (Zea mays L.) and seashore paspalum grass (Paspalum vaginatum Swartz); and the screening of sorghum genomic libraries by hybridization with SSR oligonucleotides. A total of 49 sorghum SSR-specific PCR primer pairs (two designed from GenBank SSR-containing sequences and 47 from the sequences of genomic clones) were screened on a panel of 17 sorghum and one maize accession. Ten primer pairs from paspalum and 90 from maize were also screened for polymorphism in sorghum. Length polymorphisms among amplification products were detected with 15 of these primer pairs, yielding diversity values ranging from 0.2 to 0.8 with an average diversity of 0.56. These primer pairs are now available for use as markers in crop improvement and conservation efforts.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2242
    Keywords: Key words DNA marker ; Genetic analysis ; Genetic diversity ; Genotyping ; Microsatellite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The application of simple sequence repeat (SSR) genotyping for the characterization of genetic variation in crop plants has been hindered by ready access to useful primer pairs and potentially limited conservation of the repeat sequences among related species. In this phase of work, we report on the identification and characterization of SSRs that are conserved in Brassica napus L. (rapeseed) and its putative progenitors, B. oleracea L. (cabbage, and related vegetable types) and B. rapa (vegetable and oil types). Approximately 140 clones from a size-fractionated genomic library of B. napus were sequenced, and primer pairs were designed for 21 dinucleotide SSRs. Seventeen primer pairs amplified products in the three species and, among these, 13 detected variation between and within species. Unlike findings on SSR information content in human, no relationship could be established between the number of tandem repeats within the target sequence and heterozygosity. All primer pairs have been designed to work under identical amplification conditions; therefore, single-reaction, multiplex polymerase chain reaction (PCR) with these SSRs is possible. Once moderate numbers of primer pairs are accessible to the user community, SSR genotyping may provide a useful method for the characterization, conservation, and utilization of agricultural crop diversity.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2242
    Keywords: Key words Cassava ; Microsatellites ; Fluorescence-based genotyping ; Heterozygosity ; Linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Fourteen microsatellites containing GA-repeats were isolated and characterized in cassava (Manihot esculenta Crantz, Euphorbiaceae). Microsatellite heterozygosity (h) was estimated in 48 accessions using (32P)-end-labeled primers and in more than 500 accessions using fluorescence-based genotyping. Heterozygosity values ranged from 0.00 to 0.88 and the number of alleles detected varied from 1 to 15. The reproducibility of allele sizing was also assessed using fluorescence-based genotyping. The average inter-gel size difference was 1.03 nucleotides. Chi-square tests (χ2) were performed to analyse segregation distortion and the linkage between alleles segregating from either or both parents in an F1 mapping population. Most microsatellite loci segregated in the expected 1 : 1, 1 : 2 : 1 or 1 : 1 : 1 : 1 ratio. Linkage was detected between loci segregating from either parent, and segregation distortion from the male parent was detected for locus GA-131. Approximately 80% of the microsatellites detected one or two alleles per accession, suggesting a low degree of microsatellite locus duplication, an unexpected finding for a putative allopolyploid, highly heterozygous species. The high h values of most microsatellites, their amplification in other Manihot taxa and their suitability for high-throughput, fluorescence-based genotyping, make microsatellites the marker of choice for germplasm characterization and saturation of the cassava map.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2242
    Keywords: DNA typing ; Genetic similarity ; Genetic structure ; Genetic resource conservation ; Vegetable and forage cole crops
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Effective conservation and the use of plant genetic resources are essential for future agricultural progress. Critical to this conservation effort is the development of genetic markers which not only distinguish individuals and accessions but also reflect the inherent variation and genetic relationships among collection holdings. We have examined the applicability of the random amplified polymorphic DNA (RAPD) assay for quick, cost-effective, and reliable use in addressing these needs in relation to collection organization and management. Twenty-five decamer oligonucleotide primers were screened individually with a test array composed of individuals representing a range of genetic relationships in Brassica oleracea L. (vegetable and forage cole crops). Over 140 reproducible, polymorphic fragments were generated for study. Each individual of the test array exhibited a unique molecular genotype and composites specific for accessions and botanical varieties could be established. An analysis of similarity based on amplified DNA fragments reflected the known genetic relationships among the selected entries. These results demonstrated that RAPD markers can be of great value in gene bank management for purposes of identification, measurement of variation, and establishment of genetic similarity at the intraspecific level.
    Type of Medium: Electronic Resource
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