Horizontal Gene Transmission
For centuries, humankind has made improvements to crop plants through selective breeding and hybridization, the controlled pollination of plants. Plant technology is an extension of this traditional plant breeding with one important difference, plant biotechnology allows for the transfer of a greater variety of genetic information in a more precise controlled manner. Since introduction of plant biotechnology, many farmers have planted millions of acres of biotech corn, cotton, soybeans, fruit, and other crops. While these new varieties have enhanced, crop protection reduced production costs and increased yields, raising concern among some consumers, legislators, and activists.
Many critics of agricultural biotechnology have often been dismissed. Sywanen, a professor of medical microbiology, defends the concerns of biotechnology opponents in his article titled, “In search of a horizontal gene transfer”. The impact of horizontal gene transfer concerns agricultural biotechnology critics who claim that genes inserted into domesticated organisms might be transferred to wild organisms, an example would be the transfer of antibiotic resistance marker genes to soil bacteria. Sywane’s studies of bacterial and plant phylogeny indicate horizontal gene transfer is involved in evolutionary change. A disturbing consequence of horizontal gene transfer in bacteria is the potential for antibiotic resistance, and other traits carried on plasmids to migrate from one type of bacterium to another. There has been evidence suggesting that genomic DNA is transmitted in nature. In bacteria, conjugation is the most likely mechanism responsible for gene transfer. Another research stated that transposon-like elements are likely vehicles for cutting and pasting genomic DNA from one organism to another, and that viruses may be responsible for transmitting genes between eukaryotes. Sywanen argues that some of the gene frequency studies provide weak evidence of the dangers of gene transfer because the gene was already present, so it is far from clear that its presence in genetically engineered plants will add significantly to the existing danger. He states, If horizontal transfer is found out to occur naturally, perhaps the most significant outcome would be the reshaping of our evolutionary paradigms . However Sywanen does argue, If and when experiments prove that horizontal transfer occurs, the implications will be debatable. In such scenario, some vectors might indeed create an unacceptable risk .
Another scientist that is a supporter of plant biotechnology is Jonathan Gressel. His argument is not for limiting biotechnology, but instead for encouraging responsible biotechnology geared to make GMO s safe. Much of his research has to do with herbicide resistant crops. Herbicide use may lead to artificial selection of herbicide resistant weeds due to the reproductive advantage on weeds possessing natural herbicide resistant genes. Encouragement of superweed evolution by artificial selection is not the only argument built against using herbicide resistant crops. Gressel is concerned that transgenic crops may interbreed with nearby weeds . Suggesting transgenic traits can be horizontally transferred to wild relatives of domesticated plants. Gressel criticizes GMO risk analyses that ignore the utility of GE technology designed to prevent gene transfer. He states that gene transfer could be prevented by using tandem constructs, the piggybacking of genes that affect germination by altering seed dormancy, ripening, and dissemination, with genes for the desired trait in the construct. Some other strategies include adding traits that cause dwarfing, inhibit flower production, prevent maturation, or induce pollen sterility. For instance, an antibolting trait will work well to prevent the transmission of genes in biennials such as cabbage. Gressel notes that tandem constructs can also be used for further development of crops carrying traits for insect resistance and enhanced nutritional value.
In the other hand, some groups use evidence of horizontal gene transfer as grounds to protest the continued cultivation of transgenic crops. They argue that wild plant populations are being genetically polluted with traits not normally found in the population, and that may harm wild populations by causing extinction of the species, development of pest resistant plants and loss of economically useful alleles. Several European Governments are banning the use of genetically modified crops to prevent all of these outcomes to occur.
For a conclusion, I feel that the supporters of horizontal gene transfer have the strongest argument. Horizontal gene transfer allows plants breeders to develop crops with specific beneficial traits. Many of these beneficial traits in new plant varieties fight plant pests that can be devastating to crops and others provide quality improvements.