GMO Crops in Agriculture Notes

The Need for GMO Crops

• Global population is projected to reach nine billion by 2049, posing a significant challenge to agriculture.
• Current crop yields are stagnating, while demand for food increases.
• Conventional breeding methods may not be sufficient to meet the growing demand.
• Biotechnology and GM crops can potentially fill the gap in crop production.

Golden Rice Controversy

• Anti-GMO activists destroyed field trials of Golden Rice in the Philippines.
• Golden Rice is genetically modified to deliver high levels of β-carotene (a precursor of vitamin A).
• Vitamin A deficiency leads to blindness and compromised immune systems, especially in poverty-stricken areas.
• Golden Rice aims to provide a cheap and accessible dietary source of vitamin A.

GMOs in Medicine vs. Agriculture

• GMOs are widely accepted in the medical field for producing recombinant proteins like human insulin.
• GM crops face more controversy and less acceptance compared to biopharmaceuticals.

Population Growth and Food Demand

• Global population is increasing rapidly, especially in developing countries.
• The UN FAO reported that 868 million people suffered from hunger and malnutrition in 2012.
• Agricultural production needs to increase significantly (60-100% by 2050) to meet the growing demand.
• Current rates of yield increase for major crops (maize, wheat, rice, soybean) are insufficient.

Arable Land Limitations

• The amount of arable land available for food production is finite and decreasing.
• By 2050, there will be approximately 0.18 hectares of arable land per person.
• Yield increases must come from genetic improvement or greater agricultural inputs due to land limitations.
• Climate change and water resource problems further complicate crop production.

Conventional Breeding Limitations

• Conventional breeding relies on sexual crosses to introduce new traits, which can result in yield drag.
• Backcrossing is used to dilute out negative traits, requiring many generations and years.
• Conventional breeding is limited to genetic variation within the crop's gene pool or sexually compatible relatives.

Role of Biotechnology and GMOs

• Biotechnology and GMOs can accelerate crop improvement and introduce new sources of genetic variation.
• GMO technologies offer rapid crop improvement and the ability to use genes from all sources.

Defining GMOs

• FAO defines GMOs as plants or animals produced through techniques that alter genetic material in a way that does not occur naturally.
• A more precise definition is a modification to The Cartagena Protocol definition: “Genetic Modified Organism” means any living organism that possesses a novel combination of genetic material obtained through the use of modern biotechnology.

Producing GM Crops

• Two-step process: (1) gene delivery into a plant cell (transformation) and (2) regeneration of a transgenic plant.
• Gene delivery methods include direct transfer of DNA or using Agrobacterium tumefaciens.
• Direct DNA transfer techniques include electroporation, microinjection, and microparticle bombardment.
• Microparticle bombardment (gene gun) is a common technique using pressurized helium to fire DNA-coated microparticles into plant tissue.
• Agrobacterium tumefaciens is a soil bacterium that naturally inserts genes into plants, causing cell proliferation.
• Binary vectors are used to separate the T-DNA region onto a separate plasmid for easier gene insertion.

Selectable Marker Genes

• Selectable marker genes (e.g., antibiotic resistance) are used to identify transformed cells.
• The CRE-LOX system is used to remove antibiotic marker genes from GM plants.

Impact and Safety of GM Crops

• Since 1996, GM crop acreage has steadily increased, with 433 million acres in 2013.
• Economic benefits include increased farm income ($40.7 billion from 1996-2006, $116 billion by 2012).
• Yield increases are attributed to lower weed and pest damage, as well as superior genetics.
• GM crops have contributed to a global yield increase of 377 million tons from 1996 to 2012.
• GM crops can reduce the need for land conversion for agriculture.

Herbicide Tolerance

• Herbicide-tolerant GM crops are widely adopted, with >90% of corn, soybeans, and cotton in the U.S. being GM and herbicide-tolerant.
• Issues include herbicide-resistant weeds, transgene transfer, and environmental concerns.
• Gene flow between related plant species is a natural phenomenon, and transgenes act as markers to study this process.
• Over-reliance on a single herbicide can lead to herbicide-tolerant weeds.
• Integrated weed management programs are needed to mitigate the evolution of herbicide tolerance.
• GM herbicide-tolerant crops have enabled the adoption of conservative tillage practices, enhancing soil quality.

Environmental Impact Quotient (EIQ)

• EIQ is a metric that utilizes toxicity and exposure data to derive a risk/impact value for herbicides, pesticides, and fungicides.
• GM crops have generally reduced the amount of active ingredients used and the environmental load (EIQ).

Insect Resistance

• Insect-resistant GM crops synthesize CRY protein toxins from Bacillus thuringiensis (Bt).
• Bt toxins are specific to target insects, innocuous to vertebrates, and biodegradable.
• Concerns include the development of Bt-resistant insects, transgene transfer, and environmental concerns.
• Bt-GM crop free refuges are established to combat the development of resistance.
• Stacked Bt genes (more than one CRY protein gene) are being developed to slow insect resistance.
• Bt-GM crops have resulted in a significant decrease in the use of chemical pesticides.

Biodiversity

• Broad-spectrum pesticides have negative effects on biodiversity, while Bt-GM crops generally have positive effects.
• Studies have shown that Bt-GM crops have little or no effect on soil organisms or non-target organisms.
• The deployment of Bt-GM crops has led to a reduction in insecticide deployment in some areas.

Substantial Equivalence

• Substantial equivalence is a major paradigm in the risk assessment of GM crops.
• GM crops are compared to their non-GM counterparts to ensure there are no unintended hazards.
• Approaches to assess equivalence are constantly improving, including “omics” based analyses.
• GM crops are more rigorously tested for safety than conventionally bred crops.

On the Horizon

• Next-generation GM crops address traits such as drought tolerance, pest and disease resistance, and nutrient efficiency.
• Biofortification, such as golden rice, aims to address nutrient deficiencies.

What Does the Future Hold

• Conventional breeding methods, especially with the advent of genome level technologies, designed to both generate and exploit genetic variation in order to isolate effective alleles (variants) of genes that generate yield increases.
• Agriculture is a diverse endeavor ,and if we are to be successful we need to embrace that diversity.