The Methodology And Effects Of Plant Genetic Manipulation

Method of gene modification of crops

Discuss About The Methodology Of Plant Genetic Manipulation.

Since the time immemorial, farmers are trying to minimize the negative impact of crop pests. Insects like nematodes, bacteria along with viruses and fungus causes immense destruction of crops that impose negative impact on the economy of a country. For instance, the Irish Potato famine in the 1800s, had resulted in the death of more than 1 million individuals and a large scale of emigration (Azadi et al. 2015). In early centuries, farmers used to collect seeds only from high yielding plants as a preventive measure from pests. With the advent in genetic engineering, genes from insect resistance can be moved into plants. This technology is known as Bacillus Thuringienis or Bt Technologies.

With the emergence of genetically modified crops, the question whether genetically modified crops impose positive or negative impact on the environment has raised. While Genetically Modified Crops (GMC), has the ability to help the farmers to use fewer chemical insecticides, these crop may end up misbalancing the ecosystem. According to several scientists, GM foods bear a special environmental threat and hence should be used carefully (Han et al. 2015). The National Research Council stated that improper or over usage of GM technology may leads to disastrous results. For instance, farmers who plants herbicide-resistant GM crops often give rise to herbicide-resistant superweeds. Apart from that, it has been also found that overplanting of Bt Crops has resulted in birth of a new breed off resistant insects in some fields. However, the National Research Council is not able to convince that insect-resistant GMCs are inherently riskier. According to them, insect resistant GMCs are safe as long as they are properly used (Gurau and Ranchhod 2016).

The chief purpose of this assignment is to find out whether GMC are safe for the ecosystem or not. The objectives of the report include analysis of the method of gene modification of crops, negative effect as well as the positive effect of gene modification of crops.

Considering the fact that any living organisms including plants, possess natural barrier to protect themselves against implementation of another species’ DNA, genetic engineers have to force DNA from one organism to another.

Botanists chiefly modify the gene of the crops by the six below mentioned techniques:

Crossbreeding: The mentioned technique involves cross-pollination of two sexually compatible crops in order to produce a hybrid. This technique is a primitive technique of modifying crops genetically in order to create brand new species. Some of the examples of cross breed crops are Plumcot which is a hybrid of Plum and Apricot, Limequat, which is a hybrid of lime and Kumquat and most famously Rabbage which is a hybrid of Radish and Cabbage (Klümper and Qaim 2014).

Methods of inserting Transgenes

Mutagenesis: This technique was founded by Hermann Muller, Charlotte Auerbach and J. M. Robson during the 20 the Century (Benbrook 2012). This gene modification technique results in genetic changes that can add, delete or switch nucleotides. These genetic changes are induced by radiation by the plant breeders since Mutagenesis has the capability to enhance the traits of the crop. For instance, the deeper colour in grapefruit is produced by the above-mentioned technique.

Protoplast Fusion: In this method, two plant cells which have their protoplasts removed, are taken and allowed to stick together in a chemical solution named polyethylene solution. Once the two cells got stuck together, various kinds of chemicals are added to help the cells exchange genetic information and finally create a hybrid plant cell.

Polyploidy: This technique is by plant breeders to control reproduction in plants. By this technique, sterilized seeds are soaked in colchicine in order to make them fertile. One of the examples of Polyploidy crop includes Triticale which is a hybrid of Rye and wheat (Pardo-Lopez Soberon and Bravo 2012).

Genome Editing: In this process, molecular scissors are used to cut, insert or replace genes within the seed cells. These nucleases are designed through artificial engineering so that they can be accurately placed in the desired traits or genes. One of the most common examples of Genome editing is the Herbicide tolerant Canola plant (Barrows, Sexton and Zilberman 2014). The mentioned plant is specially created by genetic engineers in order to help farmers in controlling weeds.

Figure 1: Cultivation of GMC in U.S. A.

Source (Qaim and Kouser 2013)

Two principal methods of transgene insertion are as follows:

Gene Gun: This method includes shooting transgene fragment at a very high velocity into cell or tissue of the plants. In this process, a microscopic pallet of Tungsten or gold is coated with the transgene fragment to be shot. When the pallet passes through the tissue or cell, the DNA fragment remains behind and gets incorporated into a plant chromosome in the cell nucleolus (Onstad 2013).

The Agrobacterium tumefaciens is a soil dwelling bacteria that transfers a part of its own DNA into the plant's cell and as a result, the plant suffers from Crown Gall diseases. Genetic engineers have taken the advantage of these DNA transfer mechanism while disarming the disease-causing properties. In the above-mentioned method, both bacterial cells and plants are co-cultivated in a petri dish under controlled condition (Sanvido et al. 2012). Thus genes get transferred in this process in a more controlled way compared to that of the Gene Gun method. However, one of the major disadvantages of the mentioned method is that it does not work equally well in all spices of the plant.

Negative effects of insect-resistant GMC on ecosystem

Biological control may be defined as the method of controlling pests that includes, insects, weed, mites and other plant diseases using other organisms. Unlike using artificial methods to conserve crops, the biocontrol method relies on predation, herbivory, parasitism and another natural mechanism (Rovner et al. 2015). Three basic biocontrol measures include classical control where a natural enemy of the pests are introduced in the field to kill them, inductive control, where a large population of natural enemies are administered for quick pest control and finally, inoculative control where measurements are taken to maintain the natural flow of pest enemies through regular reestablishment. However, it has been seen that insect resistant crops are causing immense damage to the bio-control agent (Li et al. 2014). Along with the pests, biocontrol agents like Tobacco hornworms and Syrphus Hoverfly Larva are getting killed when they are consuming the infected pests. This, in turn, is imposing an immense negative impact on the environment.

With the emergence of the genetically modified crop in a large scale, ecological concerns of the transgene movement from GM crop to nom-GM Counterparts as well as wild relatives have arrived. The term, pollen-mediated gene flow can be defined as a process by which pollen grains of one crop is carried to the flower of another crop for fertilities. The whole process of fertilization is performed by pollinating agents like bees and butterflies (Pardo-Lopez, Soberon and Bravo 2012).  However, during the pollination process in insect resistant GMCs, pollinators are not able to transfer pollen grains since they are getting intoxicated by the insect resistant crops. As a result, the breeding process of the crops is getting hampered which, in turn, imposes an immense negative effect on the productivity of the crops and financial condition of the farmers in the long run (Carstens et al.  2012).  

According to researchers, the insect resistant crops have alleviates the negative impact of agriculture on biodiversity (Lazebnik et al. 2017). Prior to the insect-resistant genetically modified crops, farms used to use insecticides and herbicides to prevent the destruction of crops by insects. This, in turn, imposed an immense negative impact on the environment. According to the researchers, GM crops if used in a balanced way has resulted in increased yields, decrement in the usage of insecticides, increment in the usage of more environment-friendly herbicides and finally facilitation in the adaptation of conservation tillage (Mandell et al. 2015). Thus GM crop has contributed to increased agricultural sustainability with the help of conservation tillage practices. Conservation tillage practice can be defined as a method of soil cultivation that involves leaving the crop residue of the previous year on the field before and after planting a new crop in order to reduce soil erosion. Priory this was not possible since this process used to enhance the breed of insects in the fields. Thus, it can be understood that with the emergence of insect-resistant crops, soil erosion has decreased to a great extent. Moreover, according to researchers, the potential impact of Bt crops on the soil organism is negligible. Along with that, since GM crops have enhanced the yields, the pressure of converting natural habitat into agricultural use has been greatly reduced (Rovner et al. 2015).

Pollen-mediated gene flow

A major challenge for the genetic engineers is to prevent the development of resistance o the insects to Bacillus Thurigiensis toxin produced by the insect resistant GMC. According to several theoretical models, plants that contain two dissimilar Bt toxins possess the potential to delay the development of resistance to the plant toxins in the insects (Yan et al. 2015). In spite of the fact that majority of the Bt toxins are reported to be safe for human beings, several Bt toxins can turn to harmful toxins when they get chemically combined with chemicals that are found n GE plants. Hence Bt toxins do bear a potential to adversely affect the digestive system of Human beings (Wolfenbarger and Phife 2013).

One of the most promising approaches in crop protection is RNAi that targets essential genes in insects as well as other pests. RNA interfaces can be defined as the gene regulatory process that plays a vital role in maintaining and regulating host defences against the invading viruses. The dsRNA strategy targets insect genes that can potentially provide protection to crops without the use of chemical pesticides along with offering additional advantages that include the creation of no foreign protein and the number of target genes is nearly unlimited (Tabashnik, Brévault and Carrière 2013). Thus the RNAi Anti-insect strategy can be defined as a advantage of GMC since helps the farmers to get rid of specific insects or virus that are highly dangerous for the crops.

As been discussed earlier, multiple toxins are induced in plants in order to prevent or delay the development of resistance power within the insects. Thus it can be identified as another advantageous approach of GMC. The mentioned technology, which is popularly known as Bacillus thuringiensis or Bt technology can be applied on the surface of the plants in order to provide temporary protection or is genetically engineered to produce their own Bt crystal protein (Kuiper et al. 2012). These Bt crystal proteins are highly dangerous for the pests. In recent years the usage of BT crops has got increased to a great extent due to advantages provided by it on the basis of crop protection and lower production costs. Initially, a major disadvantage of the Bt crop was the eventual resistance of the insects. However, with the multiple toxin technologies, the development of resistance of the insect to the Bt crystal toxins can be prevented to a great level.

Figure 1: Usefulness of GM crops

Source (Timmons et al. 2015)

Horizontal Gene Transfer (HGT) can be defined as a stable transfer of genetic material from one organism to another without human intervention and without reproduction. HGT involves the transmission of genes on viruses or mobile genetic elements. In spite of the fact that HGT was a matter of concern due to the spread of antibiotic resistance among pathogenic bacteria, the frequency of HGT from plants to other eukaryotes or prokaryotes has been found to be extremely low (Zhang et al. 2017). The frequency of HGT to the virus is restricted by stringent selection pressure.

Conclusion 

From the above discussion, it can be concluded that the usage of the insect-resistant genetically modified crop is safe for the environment as well as for biodiversity. As been discussed, the usage of insect resistant crop has highly reduced the usage of insecticides, pesticides and herbicides that imposes high negative impact on the biodiversity. Moreover, the mentioned technology has reduced soil erosion with the help of conservation tillage. The aim of the review was to find out whether usage of GMC is safe for the ecosystem or not. Several advantages and disadvantages of the usage of insect resistant GMCs have been discussed in this research. However, in this research, the impact of GMC on the digestive system of the human being has not been discussed. Hence there is a scope of future research on the above mentioned factor.

References

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