So, what’s next?
A succinct answer is provided here thanks to the Crop Science Society of America (CSSA): “First-generation genetically modified (GM) transgenic crops with novel traits have been grown in a number of countries since the 1990’s. Most of these crops had a single gene that allowed them to tolerate herbicide application, giving them an advantage over wild species.
Second-generation transgenic crops are now being tested in confined field trials around the world. Some of these traits will allow crops to tolerate environmental stress such as drought, cold, salt, heat, or flood. Other traits being developed may lead to increased yield or lower nutrient requirements, or increase tolerance to disease and pathogens.”
New generations of transgenic plants are being produced, as, perhaps, a way to counter potential “mid-life crises” of current GM crops.
Such “crises” include the emergence of “superweeds”, the ineffectiveness of insect resistance in some GM cotton, e.g., and the “contamination” of agricultural and natural landscapes by GM crops or by “transgene pollution” via horizontal gene transfer.
But how does one go about making such “second generation” GM plants?
More Is Better: “Trait-Stacking” & Multigene Transfer
According to the GMO Compass website: “Herbicide tolerance (HT) continues to be the most common transgenic trait in GM crops worldwide.” And “Insect resistance (mostly Bt) is the second most common genetically modified trait. Herbicide tolerance and insect resistance (Bt) often are introduced simultaneously to a crop in one transformation event. This is called trait stacking. The third most commonly grown transgenic crop was stacked insect resistant/herbicide tolerant maize. Combined herbicide and insect resistance was the fastest growing GM trait from 2004 to 2005, grown on over 6.5 million hectares in the US and Canada and comprising seven percent of the global biotech area.”
Another class of second generation GM plants is more complex phenotypically than “stacked” GM plants. Such “ambitious” phenotypes may result from the insertion of multiple genes – even artificial chromosomes called minichromosomes – into GM plants.
“Instead of attempting to generate useful transgenic plants by introducing single genes, we now see an increasing number of researchers embracing multigene transfer (MGT) as an approach to generate plants with more ambitious phenotypes. MGT allows researchers to achieve goals that were once impossible – the import of entire metabolic pathways, the expression of entire protein complexes, the development of transgenic crops simultaneously engineered to produce a spectrum of added-value compounds. The potential appears limitless.” (from reference 1 below)
So, whither plant genetic engineering? – “The potential appears limitless”!
1. Shaista Naqvi, Gemma Farré, Georgina Sanahuja, Teresa Capel, Changfu Zhu and Paul Christou (2010) “When more is better: multigene engineering in plants.” Trends in Plant Science Vol. 15, pp. 48-56. (Abstract)
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