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  • 1
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Isolates of Discula destructiva Redlin and an undescribed species of Discula, the filamentous fungi that cause anthracnose of flowering (Cornus florida L.) and Pacific (Cornus nuttalli Aud.) dogwoods, were analyzed for genetic variation by nucleic acid scanning with arbitrary mini-hairpin oligonucleotide primers. While the fungal population was highly homogeneous throughout the disease range in eastern and western North America, the generation of arbitrary signatures from amplification profiles (ASAP) distinguished isolates from the northeast, middle and southern Appalachian mountain range, and western United States and Canada. ASAP involves a dual-step arbitrary primer-based amplification procedure that generates a large number of informative allelic characters by amplification of monomorphic DNA fingerprints. ASAP analyses showed a fine fungal population structure consistent with the recent and separate introduction of the pathogen on the west and east coasts of North America.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Crop science 38 (1998), S. 1415-1424 
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Turfgrasses constitute an heterogeneous group of species differing widely in reproductive strategy, genome organization, and evolutionary history. Cultivars derived from vegetative propagation or from apomictic or self-pollinated species can be homogeneous at the genetic level, exhibiting little genetic variation. Alternatively, cultivars with an outcrossing breeding system can be genetically heterogeneous, such as those from open-pollinated seeded species. A careful study of the degree and distribution of turfgrass genetic variation is therefore essential for the efficient selection of superior plant material for breeding, an adequate management of genetic resources, and the effective preservation of biodiversity. An array of molecular techniques have targeted nucleic acids to evaluate molecular diversity at the species, population, and within-population levels. These techniques have only recently been applied to the breeding and management of turfgrass germplasm. Using the hybridization and amplification of nucleic acids, DNA profiling techniques have established patterns of genetic variation at the species level in grass systematics, and at the subspecies level in the study of natural populations, breeding lines, cultivars, and accessions. In some cases, chromosome analysis by flow cytometry and genomic in situ hybridization have notably complemented the use of nucleic acid markers. DNA profiling techniques have also assessed the genetic stability of cultivars and the appearance of offtypes, and have provided molecular estimates of turfgrass evolution. The review of current efforts to evaluate turfgrass genetic diversity clearly indicates that the application of the tools of genome analysis to the study of germplasm diversity may finally unlock the genetic potential of wild and cultivated turfgrass resources.
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 9 (1991), S. 553-557 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The surprising finding that amplification of genomic DNA can be directed by only one oligonucleotide primer of arbitrary sequence to produce a characteristic spectrum of short DNA products of varying complexity, was applied as a strategy to detect genetic differences between organisms. This ...
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 10 (1992), S. 937-937 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: The advent of a novel strategy for DNA fingerprinting that uses a single oligonucleotide to prime arbitrary segments of a DNA template to produce a characteristic set of amplified fragments promises to be of immense value in the analysis of genetic relationships.1 The idea was ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 14 (1996), S. 1668-1674 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Nucleic acids can be characterized using a variety of “fingerprinting” techniques usually based on nucleic acid hybridization or enzymatic amplification. The scanning of nucleic acids by amplification with arbitrary ollgonucleotide primers has become popular because it can generate ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 12 (1994), S. 619-623 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The enzymatic amplification of DNA directed by very short oligonucleotides of arbitrary sequence produces complex DNA profiles useful for genome analysis and identity testing. Mini-hairpins harboring a “core” arbitrary sequence at the 3′ terminus primed the amplification of a wide ...
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  • 7
    ISSN: 1432-2048
    Keywords: Agrobacterium ; Co-inoculation ; Medicago ; Mutant (Rhizobium) ; Nodulation ; Rhizobium ; Root nodule initiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nodule formation on alfalfa (Medicago sativa L.) roots was determined at different inoculum dosages for wild-typeRhizobium meliloti strain RCR2011 and for various mutant derivatives with altered nodulation behavior. The number of nodules formed on the whole length of the primary roots was essentially constant regardless of initial inoculum dosage or subsequent bacterial multiplication, indicative of homeostatic regulation of total nodule number. In contrast, the number of nodules formed in just the initially susceptible region of these roots was sigmoidally dependent on the number of wild-type bacteria added, increasing rapidly at dosages above 5·103 bacteria/plant. This behavior indicates the possible existence of a threshold barrier to nodule initiation in the host which the bacteria must overcome. When low dosages of the parent (103 cells/plant) were co-inoculated with 106 cells/plant of mutants lacking functionalnodA, nodC, nodE, nodF ornodH genes, nodule initiation was increased 10- to 30-fold. Analysis of nodule occupancy indicated that these mutants were able to help the parent (wild-type) strain initiate nodules without themselves occupying the nodules. Co-inoculation withR. trifolii orAgrobacterium tumefaciens cured of its Ti plasmid also markedly stimulated nodule initiation by theR. meliloti parent strain. Introduction of a segment of the symbiotic megaplasmid fromR. meliloti intoA. tumefaciens abolished this stimulation.Bradyrhizobium japonicum and a chromosomal Tn5 nod- mutant ofR. meliloti did not significantly stimulate nodule initiation when co-inoculated with wild-typeR. meliloti. These results indicate that certainnod gene mutants and members of theRhizobiaceae may produce extracellular “signals” that supplement the ability of wild-typeR. meliloti cells to induce crucial responses in the host.
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  • 8
    ISSN: 1432-2048
    Keywords: Feedback regulation (nodulation) ; Medicago (nodulation) ; Nodulation (spontaneous) ; Rhizobium ; Symbiosis (legume-Rhizobium)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A small subpopulation of alfalfa (Medicago saliva L.) plants grown without fixed nitrogen can develop root nodules in the absence of Rhizobium. Cytological studies showed that these nodules were organized structures with no inter- or intracellular bacteria but with the histological characteristics of a normal indeterminate nodule. Few if any viable bacteria were recovered from the nodules after surface sterilization, and when the nodular content was used to inoculate alfalfa roots no nodulation was observed. These spontaneous nodules were formed mainly on the primary roots in the region susceptible to Rhizobium infection between 4 and 6 d after seed imbibition. Spontaneous nodules appeared as early as 10 d after germination and emerged at a rate comparable to normal nodules. The formation of spontaneous nodules on the primary root suppressed nodulation in lateral roots after inoculation with R. meliloti RCR2011. Excision of spontaneous nodules at inoculation eliminated the suppressive response. Our results indicate that the presence of Rhizobium is not required for nodule organogenesis and the elicitation of feedback regulation of nodule formation in alfalfa.
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  • 9
    ISSN: 1432-2048
    Keywords: Medicago ; Mutant (Rhizobium) ; Rhizobium (host-specificity mutants) ; Root nodule initiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pairs of Rhizobium meliloti nod mutants were co-inoculated onto alfalfa (Medicago saliva L.) roots to determine whether one nod mutant could correct, in situ, for defects in nodule initiation of another nod mutant. None of the Tn5 or nod deletion mutants were able to help each other form nodules when co-inoculated together in the absence of the wild-type. However, as previously observed, individual nod mutants significantly increased nodule initiation by low dosages of co-inoculated wild-type cells. Thus, nod mutants do produce certain signal substances or other factors which overcome limits to nodule initiation by the wild-type. When pairs of nod mutants were co-inoculated together with the wild-type, the stimulation of nodulation provided by individual nodABC mutants was not additive. However, clearly additive or synergistic stimulation was observed between pairs of mutants with a defective host-specificity gene (nodE, nodF, or nodH). Each pair of host-specificity mutants stimulated first nodule formation to nearly the maximum levels obtainable with high dosages of the wild-type. Mutant bacteria were recovered from only about 10% of these nodules, whereas the co-inoculated wild-type was present in all these nodules and substantially outnumbered mutant bacteria in nodules occupied by both. Thus, these mutant co-inoculants appeared to help their parent in situ even though they could not help each other. Sterile culture filtrates from wild-type cells stimulated nodule initiation by low dosages of the wild-type, but only when a host-specificity mutant was also present. The results from our studies seem consistent with the possibility that pairs of host-specificity mutants are able to help the wild-type initiate nodule formation by sustained production of complementary signals required for induction of symbiotic host responses.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 38 (1992), S. 70-76 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary We have amplified short arbitrary stretches of total bacterial DNA to produce highly characteristic and complex DNA fingerprints. This DNA amplification fingerprinting (DAF) strategy involves enzymatic amplification of DNA directed by a single arbitrary oligonucleotide primer. Amplification produces a characteristic spectrum of products that is adequately resolved by polyacrylamide gel electrophoresis and visualized by silver staining. Although DAF is simple in concept, we found that amplification parameters must be within an optimal range for reproducibility. We establish a safe window for these parameters, which include magnesium, primer and enzyme concentration as well as cycle number. The refined procedure was used to distinguish between clinical isolates of Streptococcus uberis, Klebsiella pneumoniae, and Escherichia coli. The use of template DNA concentrations higher than 1 ng·μl−1 and high MgCl2 levels was especially important for reproductibility when amplifying small bacterial genomes. We tested a truncated Thermus aquaticus DNA polymerase, the Stoffel fragment, and found it more tolerant of reaction conditions, more efficient in the amplification of short products, and able to produce more informative fingerprints when compared to the normal thermostable polymerase from which it was derived. Because DAF produces representative fingerprints quickly and reliably from bacteria regardless of prior genetic or biochemical knowledge, we anticipate the general use of this diagnostic tool for bacterial identification and taxonomy.
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