Genetically Modified Crops
Description
Genetically Modified Crops
Genetically Modified crops have been commercially cultivated in the world since 1995. This brief outlines the background, techniques of producing GM crops, their potential benefits and associated concerns.
All living organisms—plants, animals, humans, and bacteria have DNA (Deoxyribonucleic acid). DNA contains the instructions required for life functions such as the development, survival and reproduction of an organism.
Genetic Modification (GM): Modern biotechnological techniques can directly manipulate the gene of an organism. This could be done by modifying the DNA of the organism by inserting genes from the same or another (foreign) species. The introduced gene is integrated into the organism’s genome but its location in the DNA is not known. This technique is referred to as genetic engineering and is also often called Genetic Modification (GM). The overall objective is similar to conventional breeding, i.e., to obtain desired traits.
Benefits of GM technology: GM technology has two major advantages over conventional breeding.
• First, it is faster to introduce certain traits as conventional breeding requires selection over many generations.
• Second, it enables changes in genetic makeup that may not be possible through conventional methods, such as the introduction of a gene from a different organism.
The application of GM methods in agricultural plants can result in the following benefits:
• increased yield,
• enhanced yield protection, i.e., resistance to pests and diseases,
• reduced costs for food
• reduced usage of environmentally damaging pesticides,
• enhanced nutritional value, and
• tolerance to drought hence reducing the use of groundwater.
Examples where a gene from a foreign organism was introduced in a plant include the following.
• Bt-Cotton: The bacterium Bacillus thuringiensis (Bt) produces Bt toxin which helps to kill certain pests but is not harmful to humans or other animals. The Bt-toxin genes were introduced in cotton to kill pests if they feed upon it.7
• Flavr Slavr Tomato: The anti-freezing property from an arctic fish was introduced in tomatoes to increase their shelf life.
Common GM traits in plants
GM technology has been used to introduce traits to boost crop production. Some examples are:
• Herbicide tolerance (HT): The application of herbicides to kill weeds can damage the crop too. GM crops are created with resistance to specific herbicides which can be used to manage weeds. HT crops reduce soil erosion as weed removal requires ploughing, leading to erosion. They can also be planted in weedy fields. HT crops include corn, cotton and soybeans.
• Insect resistance: Crops are created with insecticidal protein which is only harmful to certain pests that feed on them, this removes the need for the external application of chemicals. Bt-crops (cotton and corn) contain such insect-resistant traits.
• Virus resistance: Virus-resistant traits are introduced in susceptible plants which do not possess natural resistance. In the 1990s, GM Papaya was created to resist the papaya ringspot virus in Hawaii.
Traits like herbicide tolerance and insect resistance can also be combined, i.e., crops can have multiple traits (e.g., HT-Bt cotton). Other GM traits include aesthetic changes (non-browning Arctic apples) and enhanced nutritional quality (Vitamin A-rich crops such as Golden Rice).
GM Crops in World and India
The introduction of GM crops started with the approval of the Flavr Savr tomato in the USA in 1994. In 2018, GM crops were grown in 26 countries on an estimated 474 million acres (14% of the world’s arable land).
The top GM crops were soybean (50% of area sown of GM crops), maize (31%), cotton (13%), and canola or oilseed rape (5%). These numbers represent 78% of global soybean production, 76% of cotton, and 30% each of maize and canola.
USA, Brazil, Argentina, Canada, and India accounted for about 91% of the global GM crop acreage. EU grows only GM maize (mainly in Spain and Portugal).
GM Crops in India
- Bt-Cotton is the only approved GM crop (2002) for commercial cultivation. It was introduced to protect against the widespread infestation of bollworm. In 2018-19, Bt-cotton was 95% of the total cotton planted in India.
- Bt-Brinjal: In 2009, Bt-brinjal was cleared by GEAC for commercial cultivation, but it was put on a 10-year moratorium following public backlash and recommendations of brinjal growing states. Recently, GEAC has allowed field trials of new varieties of indigenously developed Bt-brinjal in eight states during 2020-23. The trial requires a no objection certificate (NOC) from concerned states and confirmed availability of isolated stretches of agricultural land.
- GM Mustard: In October 2022, GEAC approved the environmental release of GM mustard (Dhara Mustard Hybrid/DMH-11, developed in 2002) and its parental crops (Indian and east European lines). The primary objective was to obtain higher yield over its parental lines and other available mustard varieties. It is India’s first edible GM crop, and it underwent GEAC regulatory testing from 2008-2016.
GM mustard has not been released for commercial cultivation yet. The approval for environmental release is limited for four years during which it will undergo several post-environmental-release tests (e.g., performance comparison with currently available non-GM variants, effect on honeybees and pollinators). The environmental release of GM mustard has been challenged in the Supreme Court.
Regulatory Framework in India
• Environment Protection Act, 1986: Regulation of GM Crops is primarily governed by “The Manufacture, Use, Import, Export and Storage of Hazardous Micro Organisms Genetically Engineered Organisms or Cells Rules, 1989”
• Review Committee on Genetic Manipulation (RCGM): Under the Department of Biotechnology (DBT), this committee monitors various aspects of R & D projects involving GM organisms.
• Genetic Engineering Appraisal Committee (GEAC): Under the Ministry of Environment, it is responsible for the assessment of proposals related to the release of GM organisms and products into the environment.
• GEAC Safety Assessment tests: Molecular characterisation (study of inserted genes), food safety studies (protein analysis, toxicity and allergenicity tests) and Environmental safety studies (field trials, Biosafety Research Level trials, impact on soil, pollen flow studies).
GEAC recommendations are considered by Environment Ministry which decides on the final approval of GM organisms and products. In India, gene-edited crops are exempted from biosafety assessment and they will be released as new varieties.
GM Regulatory Approaches in the World
• United Nations Cartagena Protocol on Biosafety (2000): Signatory countries may take a decision to minimise potential adverse effects on biological diversity and risks to human health with regard to import of living (genetically) modified organisms.
• USA: If the new variety, made with gene-editing technology could be bred using conventional methods, it does not require regulatory approval (only valid for single modification). Regulatory approval focuses on the traits rather than on the technology used.
• European Union: Evaluation of risks associated with new GM products is process-based, i.e., it depends on whether or not they were developed using GM methods. Gene-edited crops are also regulated as GM crops.
• Canada: All newly developed crops, whether GM or conventionally bred, go through the same risk assessment.
Concerns about GM Crops
While allowing GM crops, it may be necessary to ensure that certain adverse consequences do not arise. Some of the important issues include effect on human health and the impact on the environment and biodiversity. However, due to the complexity associated with the long-term assessment of environmental impacts, it may be difficult to reach definite conclusions.
• Impact on Human Health
Before any food produced from GM crops is permitted in the market, several safety tests must be completed. Based on decades of data and studies, the scientific community is in agreement that the currently available GM crops are as safe to consume as non-GM crops.
An example of potential adverse effect of a GM trait on human health comes from Australia. Toxins from beans were put in field peas to kill insects which used to destroy almost 30% of the yield. The feeding trials on animals indicated negative results, and the development of GM field peas was discontinued. Hence, the need for a robust regulatory framework becomes significant.
• Impact of herbicide-tolerant and pest-resistant crops
Overuse of herbicides on fields with herbicide-tolerant GM or non-GM crops can allow weeds to develop resistance against them. Glyphosate has been used as a herbicide in the USA since 1974, and its extensive use has led to glyphosate-resistant weeds.
a) Impact on soil
Most herbicides degrade quickly in the soil but the rate of degradation depends on soil temperature and moisture levelsThe time of application and amount of dosage in recommended limits of herbicides is critical for getting effective results with minimal impact on soil. However, some studies have reported undesired effects of herbicide residue on soil.
b) Impact of pest resistance
Similar to the case of weeds and herbicides, pests can develop resistance to pest-resistant traits such as the Bt toxins produced by the GM crop.
c) Impact on genetic diversity in crop varieties
Concerns have been raised regarding the potential of GM crops to reduce the genetic diversity of neighbouring crops, close relatives, and weeds. Genetic diversity is crucial for adapting to new environments, and as a protection of the species against diseases.
GM crops may crossbreed (physical contact with neighbouring plants, pollen transfer by insects or wind) with non-GM varieties of the same crop and other wild relatives. Such crossbreeding might be problematic if it results in a wild relative crop acquiring unwanted characteristics (weediness, invasiveness). Also weeds could cross breed with HT crops and result in herbicide-tolerant weeds.
d) Effect on honeybees and other pollinators
There is a concern that GM crops may pose a potential risk to the honeybee population and other pollinatorsA few focused scientific studies have not found any direct negative impact on the honeybee population by GM Canola and Bt Crops. However, HT crops may lead to the overuse of herbicides which may indirectly affect the weed population of an area and thus reduce the availability of pollen or nectar.60,63 For example, some studies indicate the negative impact of HT crops on the population of the monarch butterfly in the USA; other studies contest these findings and there is no consensus among scientists
GM Mustard (DMH-11)
The objective of using GM technology in mustard is to improve yields by crossing an Indian variant (Varuna) with a European line Early Heera (EH)-2. This is difficult to do by conventional breeding because mustard is self-pollinating, i.e., the pollen from the male part pollinates and fertilises the female part of the same plant. This makes it difficult to cross one variant of plant with a different variant.
To overcome this problem, the gene barnase is inserted in the Varuna plant which makes it male sterile (no pollen formation). This can now be crossed with EH-2. However, the plant growing from the resultant seed will be male-sterile and cannot produce any seed through self-pollination. Therefore, another gene barstar which restores male fertility is added to EH-2 before crossing. Thus, the new barstar-barnase variant can self-pollinate and produce mustard seeds, which is the desired crop.
As the process of adding the gene is probabilistic (only a few of the target plants get the gene added), another herbicide-tolerant gene bar is added along with barstar and barnase. The resultant (growing) plants are then sprayed with herbicide, and only those containing bar gene (and therefore with barnase and barstar) survive. Therefore, the seeds will have bar-barnase-barstar genes. This seed has been named Dhara Mustard Hybrid (DMH)-11.
