For many years major challenge for scientists has been developing the resistant varieties against pests in plants. However, this approach seems now inefficient due to a number of reasons and alternatively, genetic engineering for improving crop pest and disease resistance is being actively followed these days by the plant scientists, world-over. New tools and genes have been developed for use in the genetic engineering of plants to introduce effective resistance to biotic stresses and to understand the mechanisms of resistance.
Recent advances in genetic engineering, Bacillus thuringiensis Bt has resulted in successful control of many economically important pests in food crops. This approach should allow increases in both productivity and quality of plants in an environmentally friendly manner, thereby reducing the use of and reliance on chemical control of pests. Wilczek Progenies through Agroinoculation. How to cite this article: A. Karthikeyan, R. Valarmathi, S. Nandhakumar, Genetically Modified Crops: Insect Resistance.
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Biotechnology, DOI: Full Name:. Plants use non-photochemical quenching to protect them from excessive amounts of sunlight. Plants can switch on the quenching mechanism almost instantaneously, but it takes much longer for it to switch off again. During the time that it is switched off, the amount of energy that is wasted increases.
The plants had larger leaves, were taller and had more vigorous roots. Another improvement that can be made on the photosynthesis process with C3 pathway plants is on photorespiration. Some GM soybeans offer improved oil profiles for processing. A genetically modified cassava under development offers lower cyanogen glucosides and enhanced protein and other nutrients called BioCassava.
In November , the USDA approved a potato that prevents bruising and produces less acrylamide when fried. Plants have been engineered to tolerate non-biological stressors , such as drought ,     frost ,  and high soil salinity. Drought resistance occurs by modifying the plant's genes responsible for the mechanism known as the crassulacean acid metabolism CAM , which allows the plants to survive despite low water levels.
This holds promise for water-heavy crops such as rice, wheat, soybeans and poplar to accelerate their adaptation to water-limited environments. As of , the most prevalent GM trait was glyphosate -tolerance. The shikimate pathway is not present in animals, which instead obtain aromatic amino acids from their diet. This trait was developed because the herbicides used on grain and grass crops at the time were highly toxic and not effective against narrow-leaved weeds.
Thus, developing crops that could withstand spraying with glyphosate would both reduce environmental and health risks, and give an agricultural edge to the farmer. This transit peptide was used because it had shown previously an ability to deliver bacterial EPSPS to the chloroplasts of other plants. The DNA was injected into the soybeans using the particle acceleration method. Soybean cultivar A54O3 was used for the transformation.
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Tobacco plants have been engineered to be resistant to the herbicide bromoxynil. Crops have been commercialized that are resistant to the herbicide glufosinate , as well. Monsanto has requested approval for a stacked strain that is tolerant of both glyphosate and dicamba. The request includes plans for avoiding herbicide drift to other crops. However, these conditions typically only occur during June and July for a few hours at a time. Tobacco, corn, rice and some other crops have been engineered to express genes encoding for insecticidal proteins from Bacillus thuringiensis Bt.
This represents a In the late s, a genetically modified potato that was resistant to the Colorado potato beetle was withdrawn because major buyers rejected it, fearing consumer opposition. Papaya, potatoes, and squash have been engineered to resist viral pathogens such as cucumber mosaic virus which, despite its name, infects a wide variety of plants. Potatoes were engineered for resistance to potato leaf roll virus and Potato virus Y in Poor sales led to their market withdrawal after three years.
Yellow squash that were resistant to at first two, then three viruses were developed, beginning in the s. Squash was the second GM crop to be approved by US regulators. The trait was later added to zucchini. Many strains of corn have been developed in recent years to combat the spread of Maize dwarf mosaic virus , a costly virus that causes stunted growth which is carried in Johnson grass and spread by aphid insect vectors. These strands are commercially available although the resistance is not standard among GM corn variants.
In , the FDA approved the first plant-produced pharmaceutical , a treatment for Gaucher's Disease. Algae is under development for use in biofuels. Lignin is the critical limiting factor when using wood to make bio-ethanol because lignin limits the accessibility of cellulose microfibrils to depolymerization by enzymes. Companies and labs are working on plants that can be used to make bioplastics. Scientists at the University of York developed a weed Arabidopsis thaliana that contains genes from bacteria that could clean TNT and RDX -explosive soil contaminants in However A.
Genetically modified plants have been used for bioremediation of contaminated soils.
Mercury , selenium and organic pollutants such as polychlorinated biphenyls PCBs. Marine environments are especially vulnerable since pollution such as oil spills are not containable. In addition to anthropogenic pollution, millions of tons of petroleum annually enter the marine environment from natural seepages. Despite its toxicity, a considerable fraction of petroleum oil entering marine systems is eliminated by the hydrocarbon-degrading activities of microbial communities.
Particularly successful is a recently discovered group of specialists, the so-called hydrocarbonoclastic bacteria HCCB that may offer useful genes. Crops such as maize reproduce sexually each year.https://inerrake.tk
Genetically Modified Plants: Public and Scientific Perceptions
This randomizes which genes get propagated to the next generation, meaning that desirable traits can be lost. To maintain a high-quality crop, some farmers purchase seeds every year. Typically, the seed company maintains two inbred varieties and crosses them into a hybrid strain that is then sold. Related plants like sorghum and gamma grass are able to perform apomixis , a form of asexual reproduction that keeps the plant's DNA intact.
This trait is apparently controlled by a single dominant gene, but traditional breeding has been unsuccessful in creating asexually-reproducing maize. Genetic engineering offers another route to this goal. Successful modification would allow farmers to replant harvested seeds that retain desirable traits, rather than relying on purchased seed. Genetic modifications to some crops also exist, which make it easier to process the crop.
Emulsifiers in packaged foods . Soybean oil . The number of USDA-approved field releases for testing grew from 4 in to 1, in and averaged around per year thereafter. Releases with agronomic properties such as drought resistance jumped from 1, in to 5, in As of September , about 7, releases had been approved for corn, more than 2, for soybeans, more than 1, for cotton, and about for potatoes.
Constant exposure to a toxin creates evolutionary pressure for pests resistant to that toxin. Over-reliance on glyphosate and a reduction in the diversity of weed management practices allowed the spread of glyphosate resistance in 14 weed species in the US,  and in soybeans. To reduce resistance to Bacillus thuringiensis Bt crops, the commercialization of transgenic cotton and maize came with a management strategy to prevent insects from becoming resistant.
Insect resistance management plans are mandatory for Bt crops. The aim is to encourage a large population of pests so that any recessive resistance genes are diluted within the population. Resistance lowers evolutionary fitness in the absence of the stressor, Bt. In refuges, non-resistant strains outcompete resistant ones.
As a result, the resistance gene frequency in the population remains lower. For example, if the temperature is not ideal, thermal stress can lower Bt toxin production and leave the plant more susceptible. More importantly, reduced late-season expression has been documented, possibly resulting from DNA methylation of the promoter.
This success has depended on factors independent of management strategy, including low initial resistance allele frequencies, fitness costs associated with resistance, and the abundance of non-Bt host plants outside the refuges. Companies that produce Bt seed are introducing strains with multiple Bt proteins. Monsanto did this with Bt cotton in India, where the product was rapidly adopted.
The Future of GMO Food
Coined "Refuge-In-a-Bag" RIB , this practice is intended to increase farmer compliance with refuge requirements and reduce additional labor needed at planting from having separate Bt and refuge seed bags on hand. Increased concerns for resistance with seed mixtures include partially resistant larvae on a Bt plant being able to move to a susceptible plant to survive or cross pollination of refuge pollen on to Bt plants that can lower the amount of Bt expressed in kernels for ear feeding insects.
Best management practices BMPs to control weeds may help delay resistance. BMPs include applying multiple herbicides with different modes of action, rotating crops, planting weed-free seed, scouting fields routinely, cleaning equipment to reduce the transmission of weeds to other fields, and maintaining field borders.
By some weed populations had evolved to tolerate some of the same herbicides. Palmer amaranth is a weed that competes with cotton. A native of the southwestern US, it traveled east and was first found resistant to glyphosate in , less than 10 years after GM cotton was introduced. Farmers generally use less insecticide when they plant Bt-resistant crops. Insecticide use on corn farms declined from 0.
This is consistent with the decline in European corn borer populations as a direct result of Bt corn and cotton. The establishment of minimum refuge requirements helped delay the evolution of Bt resistance.