The roots of plant biotechnology can be traced back to the time when humans started collecting seeds from their favorite wild plants and began cultivating them in tended fields. It appears that when the plants were harvested, the seeds of the most desirable plants were retained and replanted the next growing season. While these primitive agriculturists did not have extensive knowledge of the life sciences, they evidently did understand the basic principles of collecting and replanting the seeds of any naturally occurring variant plants with improved qualities, such as those with the largest fruits or the highest yield, in a process that we call artificial selection. This domestication and controlled improvement of plant species was the beginning of plant biotechnology. This very simple process of selectively breeding naturally occurring variants with observably improved qualities served as the basis of agriculture for thousands of years and resulted in thousands of domesticated plant cultivars that no longer resembled the wild plants from which they descended.
The second era of plant biotechnology began in the late 1800's as the base of knowledge derived from the study of the life sciences increased dramatically. In the 1860's Gregor Mendel, using data obtained from controlled pea breeding experiments, deduced some basic principles of genetics and presented these in a short monograph modestly titled "Versuche tiber Pflanzenhybriden" (in Verhandlungen des naturforschenden Vereins, 1866; Experiments with Plant-Hybridisation, 1910). In this publication, Mendel proposed that heritable genetic factors segregate during sexual reproduction of plants and that factors for different traits assort independently of each other. Mendel's work suggested a mechanism of heritable factors that could be manipulated by controlled breeding of plants through selective fertilization and also suggested that the pattern of inheritance for these factors could be analyzed or, in some cases, predicted by the use of mathematical statistics.
These findings complemented the work of Charles Darwin, who expounded the principles of descent with modification and selection as the chief factor of evolutionary change in his 1859 book On the Origin of Species by Means of Natural Selection. The application of these principles to agriculture resulted in deliberately produced hybrid varieties for a large number of cultivated plants via selective fertilization. These artificially selected hybrids soon began to benefit humankind with tremendous increases in both the productivity and the quality of food crops.
Genetic Engineering
The third era of plant biotechnology involves a drastic change in the way crop improvement may be accomplished, by direct manipulation of genetic elements.
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Public Concern
It is perhaps this lack of natural boundaries for genetic exchange that seems so foreign to conventional scientific thought and that makes plant genetic engineering controversial.
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Economic Goals
To what end are humans genetically engineering plants?
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Nutritional Goals
Additionally, some products appearing in the scientific literature but awaiting commercialization have the potential to dramatically improve human nutritional deficiencies, which are especially prevalent in developing countries.
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Novel Products
Novel products include those not traditionally associated with plants and are limited only by imagination and currently available techniques.
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Plant Tissue Cultures
Central to plant biotechnology is the use of in vitro methods. Researchers use plant tissue cultures, for example, to grow plant cells on sterile nutrient media.
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Micropropagation
Micropropagation, another biotechnology technique, is the production of many clonal plants using tissue culture methods.
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Steps in Genetic Engineering
The first genetically engineered plants, tobacco plants, were reported in the scientific literature in 1984.
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Plant Transformation Methods
Currently plant transformation with foreign genes may be accomplished by several proven methods, including bacteria mediated transfer, microparticle bombardment, electroporation, microinjection, sonication, and chemical treatment.
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Selection of Transformed Plant Cells
Selecting the few transformed plant cells out of all the plant cells in an explant requires some advance planning.
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Regenerating Whole Transformed Plants
After successfully getting a gene construct into a plant cell and selecting the transformed cells, it is possible to get the plant cells to multiply in tissue culture.
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