The fruits and vegetables we eat today are the product of hundreds of years of genetic mutation and modification. Contemporary tomatoes are almost 20 times larger than their ancestors or counterparts in the wild, and today’s plants have much higher yields.
The journey from wild to domesticated began as early as 11,000 years ago as our ancestors shifted from hunting and gathering to agriculture. So began the long process of plant genetic modification, as growers began the use of artificial selection to save seeds from the most desirable plants each year.
Dr. Diane Beckles, associate professor and associate plant biologist at the University of California, Davis Department of Plant Sciences, asserts, “Everything we grow now developed from thousands of years of natural mutations or mistakes in the code.” When mistakes had positive results—such as making plants easier to grow or cultivate, she says, “It also made them more productive, better yielding, better tasting, and so on.” So the food we eat today is the product of generations of genetic mutation and artificial selection.
The Evolution of TILLING
TILLING, or targeted induced local lesions in genomes, may be thought of as the process of artificial selection—merely sped up. An official definition from the University of California, Davis’ Genome Center describes TILLING as “a general reverse genetic technique that uses traditional chemical mutagenesis methods to create libraries of mutagenized individuals that are later subjected to high-throughput screens for the discovery of mutations.”
In more basic terms, TILLING involves exposing a large seed sample to various physical or chemical agents to observe the mutations that occur. By selecting the favorably mutated seeds to begin the next wave of experiments, plant biologists can accelerate the process.
The scientific process of TILLING involves exposing anywhere between 10,000 to 20,000 seeds to influencing agents to cause mutations. Researchers typically do not know what mutations will occur or even if they will be useful. “We don’t really know where these changes are happening or what the result will be,” Dr. Beckles confirms. “We just know that we’re randomly introducing changes.”
Although methods for mutagenesis are not new, recent advances in DNA harvesting have created an opportunity for TILLING to be a viable solution to improve crop quality, or create new varieties without inserting or removing genes through genetic modification. The technology of DNA extraction has come such a long way that researchers can now extract strands from thousands of plants in a single day.
The fruits and vegetables we eat today are the product of hundreds of years of genetic mutation and modification. Contemporary tomatoes are almost 20 times larger than their ancestors or counterparts in the wild, and today’s plants have much higher yields.
The journey from wild to domesticated began as early as 11,000 years ago as our ancestors shifted from hunting and gathering to agriculture. So began the long process of plant genetic modification, as growers began the use of artificial selection to save seeds from the most desirable plants each year.
Dr. Diane Beckles, associate professor and associate plant biologist at the University of California, Davis Department of Plant Sciences, asserts, “Everything we grow now developed from thousands of years of natural mutations or mistakes in the code.” When mistakes had positive results—such as making plants easier to grow or cultivate, she says, “It also made them more productive, better yielding, better tasting, and so on.” So the food we eat today is the product of generations of genetic mutation and artificial selection.
The Evolution of TILLING
TILLING, or targeted induced local lesions in genomes, may be thought of as the process of artificial selection—merely sped up. An official definition from the University of California, Davis’ Genome Center describes TILLING as “a general reverse genetic technique that uses traditional chemical mutagenesis methods to create libraries of mutagenized individuals that are later subjected to high-throughput screens for the discovery of mutations.”
In more basic terms, TILLING involves exposing a large seed sample to various physical or chemical agents to observe the mutations that occur. By selecting the favorably mutated seeds to begin the next wave of experiments, plant biologists can accelerate the process.
The scientific process of TILLING involves exposing anywhere between 10,000 to 20,000 seeds to influencing agents to cause mutations. Researchers typically do not know what mutations will occur or even if they will be useful. “We don’t really know where these changes are happening or what the result will be,” Dr. Beckles confirms. “We just know that we’re randomly introducing changes.”
Although methods for mutagenesis are not new, recent advances in DNA harvesting have created an opportunity for TILLING to be a viable solution to improve crop quality, or create new varieties without inserting or removing genes through genetic modification. The technology of DNA extraction has come such a long way that researchers can now extract strands from thousands of plants in a single day.
Through the process of mutagenesis more than 2,000 plant species have been created over the past 50 years, according to Dr. Beckles. A well-known example of its success is the Ruby Red grapefruit. This particular variety came from a natural mutation within a grapefruit tree, which was used as the basis for further TILLING to create an even deeper red coloring.
Comparing TILLING and Genetic Modification
By process, TILLING is much faster than traditional crossbreeding. Scientists have been crossbreeding plants for years, from Gregor Mendel’s plant hybrids (considered the beginning of modern genetics) to mutation breeding.
In classical crossbreeding, two plants such as a mildew-resistant pea and a high yielding pea may be crossbred to produce a high yielding, mildew-resistant variety.
Crossbreeding typically aims to improve a plant’s survivability so it may continue to maturity and provide maximum yield. Despite its many advantages, however, the crossbreeding process is slow and often takes many years to produce a plant with the desired characteristics.
Genetic modification (GM), the process of inserting or removing genes from an organism’s genome—began in the 1980s and expanded rapidly in the 1990s. Genetically modified crops have changed the world by providing plants able to withstand the devastating effects of drought or pest infestation. According to the International Service for the Acquisition of Agri-Biotech Applications, there were 175.2 million hectares of GM crops growing in the world in 2013.
The highest acreage of biotech crops is in the United States, made up of 70.1 million total hectares of maize, soybeans, cotton, canola, sugar beets, alfalfa, papaya, and squash. As a relatively new scientific process, it has become increasingly controversial as consumers worry about the repercussions of genetic modification—such as long-term effects on health and the environment.
Although TILLING involves influencing plant DNA, the process is distinctly different from genetically modified crop development. TILLING does not involve genetic engineering but rather genetic mutation. Genetically modified crops have extra, fewer, or modified genes, while the TILLING process does not add or remove genes and only works with genes already existing within an organism.
“The advantage with TILLING,” Dr. Beckles emphasizes, is “you haven’t added any DNA to the plant. All you’ve done is exposed it to agents that would cause mistakes in the gene pool.” Given the rising objections to GM plants, TILLING could be the wave of the future.
Applications, Benefits, and Risks
As a way to create plants with desirable characteristics—without the long timeframe of classical crossbreeding or the negative shadow of genetic engineering—TILLING is gaining favor both within and outside the scientific community.
A number of universities around the world are conducting TILLING experiments, from the University of California, Davis (projects with Arabidopsis thaliana [related to the Brassicaceae family of plants like mustard and cabbage], rice, tomatoes, and wheat) to India’s University of Hyderabad (tomatoes), as well as the National Institute for Agricultural Research in Paris, France (tomatoes and peas), West Lafayette, Indiana’s Purdue University (corn), and Southern Illinois University in Carbondale (soybeans).
In addition to university trials, the German Federal Ministry of Research has also been involved in multiple projects, using TILLING to improve qualities in grain, potatoes, and sugar beets. Stateside, Arcadia Biosciences, Inc. continues to work on several TILLING applications to enhance taste and extend shelf life. Early experiments with tomatoes were promising, and Arcadia is reportedly working on other commodities as well, including projects with lettuce, melons, and strawberries.
The use of TILLING could have a profound impact on the produce industry, such as extending shelf life for certain fruits by as much as an additional two weeks. Though this has already been achieved with some genetic engineering projects,
TILLING provides a path to improve fruits and vegetables without the public outcry and controversy.
Current crops typically used in TILLING include wheat, rice, soybeans, and maize, but there is room for fresh produce in the mix from tomatoes to melons or even peas. Dr. Beckles believes higher-volume crops (like melons) are the best candidates for TILLING because the process is rather expensive.
Despite its promise, there are risks and detractions to TILLING. Valuable characteristics cannot be added where they do not exist—which is possible with GMO varieties, such as the much-talked about nonbrowning Arctic apple—but time can be considerable due to the random nature of some mutations.
According to a March 2010 article in the European newsletter GMO Compass, “the random nature of the first-step mutations means that many plant genes may not function as they should.” Such occurrences slow the process and can hamper progress, creating plants with more undesirable than favorable characteristics. Because of this lack of precision, researchers can lose valuable time and money.
Regulatory Atmosphere
As previously noted, GM and TILLING are completely different methods for altering plant DNA. Due to this fundamental difference, the regulatory environment for TILLING-related crops is much less rigid. The more relaxed regulatory atmosphere has allowed for easier integration of TILLING into the agriculture industry. Additionally, environmental organizations such as Greenpeace are less opposed to TILLING than GM methods.
This is not the case, however, in Canada. Ottawa, Ontario-based Health Canada is more strict when it comes to any type of “mutation breeding” or biotechnology, which creates what are characterized as “novel foods.”
Any such processes and the resulting products require a “pre-market food safety assessment,” the first step in a stringent regulatory approval process. The True North also has tighter labeling restrictions than the United States, requiring any type of genetic engineering or modification to be listed on product labels.
Nevertheless, the University of British Columbia in Vancouver has been working on its own TILLING project (called “CAN-TILL,” the Canadian TILLING Initiative) for several years, related to the Brassicacace family of plants.
Final Thoughts
While TILLING could prove a valuable resource for the produce industry by fostering varieties with higher productivity and extended shelf life, GM plants can provide some of the same benefits.
If consumers are looking for a more ‘natural’ process, TILLING, like crossbreeding, fits the bill. Though TILLING is much faster than its predecessor, it is not without risks and requires considerable investment.
Despite the drawbacks, Dr. Beckles believes the benefits of TILLING could be tremendous—from increasing output and productivity, to creating better quality and longer lasting produce, to even reducing waste and environmental costs. For growers, the bottom line is much simpler: higher yields plus superior product equals happy customers.
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