Managing Global Genetic Resources Agricultural Crop Issues and Policies (1993) / Chapter Skim
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7. Biotechnology and Germplasm Conservation
7. Biotechnology and Germplasm Conservation
Pages 189-204
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From page 189... ...
technology, it is used here in a broader sense to include tissue culture, cryopreservation, plant micropropagation, and animal regeneration from early embryos. Biotechnology influences germplasm conservation in several ways.
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From page 190... ...
In vitro cell and tissues cultures are providing new approaches to multiply germplasm resources and open opportunities for long-term cryopreservation. In Vitro Conservation of Plants The germplasm of vegetatively propagated crops is normally stored and shipped as tubers, corms, rhizomes, roots, or in the case of woody perennials, as cuttings.
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From page 191... ...
~: ~ ~ ~~ ~ _ s A..: a. J Advances in biotechnology provide tools for conserving and managing plant genetic resources.
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From page 192... ...
Stress is an intrinsic factor in slow growth, and little is known about its effect on somaclonal variation. What began as a clonal culture may change into a population of cells consisting of the original genotype plus variant genotypes.
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From page 193... ...
No conservation collections or germplasm banks are yet using cryopreservation for non-seed germplasm storage, although several are involved in cryopreservation research. Collecting Germplasm In Vitro The laboratory facilities required for in vitro culture normally include a sterilizer, a laminar flow hood (to provide a clean, sterile
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From page 194... ...
Although there is some potential for using in vitro collection for vegetatively propagated crops and those with short-lived seeds, there are serious implications for plant quarantine since the collected explants may carry pests or pathogens that might well be detected or excluded in material cultured by more rigorous methods. In Vitro Exchange of Germplasm During the past 20 years, advances in tissue culture technology have led to the development of commercial micropropagation, a relatively new industry that supplies young plants for a variety of horticultural, agronomic, and plantation crops (Constantine, 1986~.
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From page 195... ...
They can be stored in the dark for more than 4 months, and the recipient can plant them directly into pots or nursery beds without a further culture step. In modern potato breeding programs, in vitro cultures provide a disease-free reference collection during the years of field testing needed to select the most desirable clones.
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From page 196... ...
Generally one embryo is transferred per recipient in cattle and horses, two in sheep and 20 in pigs. Related technologies allow in vitro fertilization, embryo sex determination, splitting of embryos into parts to produce identical clones, and the creation of chimeras by associating cells derived from embryos of different genotypes.
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From page 197... ...
For economic and technical reasons it is unlikely, in the foreseeable future, that gene synthesis will make the physical storage of germplasm in the form of seeds, whole plants, or tissue cultures obsolete. The conservation of DNA and the assembly of sequence data bases are not alternatives to conventional germplasm conservation because they are not coordinated in a genome (Peacock, 1984~.
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From page 198... ...
DNA Sequence Data Banks There is now so much DNA sequencing carried out in various laboratories worldwide that the ability to compare new sequences with those that have already been described and well characterized is of considerable importance. Comparisons may suggest unsuspected functions or may reveal useful homologies between unrelated organisms.
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From page 199... ...
The same digest tested with different DNA probes shows different band patterns that are also constant and characteristic for each probe. When the DNA digests from separate organisms are compared, the differences in banding patterns are called restriction fragment length polymorphisms (RFLPs)
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Polymerase Chain Reaction The polymerase chain reaction (PCR) is an extremely sensitive and accurate method for recovering microgram amounts of single specific DNA sequences present in biological samples at very low concentrations.
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From page 201... ...
PCR analyses will be useful for comparative genetic studies, which, until now, have depended on morphological or chemical comparisons rather than functional genetic analyses using the tools of molecular biology. As with isolated DNA, cloned DNA, and DNA sequence information stored in data banks, the DNA of inviable specimens and cryogenically stored tissues cannot be used directly to reconstitute an organism.
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From page 202... ...
RECOMMENDATIONS Recent advances in biotechnology provide powerful tools for conserving, evaluating, and using genetic resources. Cloned DNA fragments and synthetic DNA are unlikely to replace conventionally stored seeds and other germplasm in the foreseeable future.
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From page 203... ...
The rapid development of DNA sequence data banks, plasmid libraries, and cloned DNA fragments has created a genetic resource of growing size and importance. However, with this expansion comes a vast amount of data and information.
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From page 204... ...
DNA sequences used as probes can detect viruses in germplasm bank materials and also reveal RFLPs that can be used to construct linkage maps and, as linked markers, to select desirable traits. Linked RFLP markers might be used to detect genes for resistance to pests and pathogens that themselves cannot be used because of quarantine restrictions.
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