Improving Stress Resistance in Agricultural Crops

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Table of Contents

Introduction
The Need for Improvement in Stress Resistance
The Basic Biological Principles used in the Development of the Technology
The Use of the Technology
Abiotic Stress Resistance
The Negative Effects of the Technology
Conclusion
References

Introduction

Agricultural crops are often exposed to many different environmental stressors. These may be either abiotic, such as drought or extreme temperatures, or biotic, such as diseases or pest damage. By improving stress resistance in these crops would allow producers to grow various essential crops in areas subjected to negative climate conditions (extreme temperatures, droughts) and areas with poor soil. Stress resistance improvement would also contribute to increased productivity.

An increase in the number of crops grown would assist in preventing famine in many poor countries. The biotechnology involved in producing such crops faces many difficulties and there are a lot of considerations of the methods used to improve the crop’s resistance that need to be assessed. Many claim that some techniques can be harmful to the environment and people’s health. For instance, the creation of new species or the introduction of new features in existing plants can damage the biological diversity, since new plants can suppress existing species.

Moreover, this may also lead to damage to the food chain. Finally, many scientists insist there are ambiguities in genetically modified (GM) crops since the long-term consequences of such use are still unknown. Nevertheless, the invention of new strategies and techniques to improve crop resistance should be continued, as the worlds’ population may already be facing the problem of famine, which may become more serious without the development of agricultural species.

The Need for Improvement in Stress Resistance

Agricultural technology has been introduced to solve the imminent problem faced in the agricultural sector: improving crop resistance to biotic and abiotic stressors. Some other problems technology has to address include time, expenses, food safety, environmental impact, land transformation, and nutrient concentration.

Abiotic stressors

Not all regions are appropriate for the growing of agricultural crops, as conditions including extremely high or low temperatures, droughts and salinity make it inefficient. These unfavorable conditions prevent crops from growing fast and decrease the plants’ productivity. For instance, rice can resist high temperatures and floods, but it cannot grow in areas subjected to droughts (VBI, 2008, p.16). However, the need for such an important basic crop is increasing due to the problem of increasingly imminent food shortages in some areas of the world. It is essential, therefore, to create such species which could be productive in drought-stricken regions. This could solve many problems associated with famine and is partly why scientists try to work out various methods to improve crops resistance to such stressors.

Resistance to drought and low temperatures is known to be improved with accumulation of such compounds as osmoprotectants (Gupta, 2009, p.469). Crops such as tomatoes, potatoes and rice cannot accumulate this component; however, these crops can be made to accumulate it by manipulating the glycine betaine biosynthetic pathway, through transgenesis (Gupta, 2009, p.469). This process includes transmission of a certain gene (a transgene) to an organism so that it acquires a new property and can fight illnesses and bacteria due to the increased resistance. This organism can pass this property to its offspring so that they demonstrate good resistance to those external factors as well.

A common practice for improving drought resistance is to use wild species. For instance, drought resistance of sunflowers was increased with the help of breeding (Škorić, 2009). The wild Helianthus species were used, since they possess the necessary features; high resistance to drought and salinity. The process was effective and it was decided to use it to increase crops. As reported by Dita et al. (2006), these technologies have identified specific molecular markers that may be used in breeding programs through Marker-Assisted Selection (MAS) to enhance stress tolerance. In other words, scientists traced the gene that was responsible for a certain feature in the organism with the help of molecular markers, and pulled it from that organism to share with other organisms as well.

Biotic Stressors

It is not only unfavorable climate which can negatively affect a crops growth. Apart from abiotic stressors, crops can suffer the influence of biotic stressors such as disease or pest damage. A very effective technique to improve crop resistance to biotic stressors is hybridizations. For example, in the improvement of wheat resistance, scientists singled out characteristics necessary for tolerance to biotic factors which were present in the nearest wild wheat relatives. This can be explained in the example of two species, Medicago truncatula and Lotus japonicas, that were used for exploration of biotic and abiotic resistance and tolerance (Dita et al., 2006, p.2).

Successful hybrids were obtained which were highly resistant to major biotic stressors such as rusts, powdery mildew, bunt, Russian wheat aphid, oat aphid, greenbug, and wheat nematodes (Anguina tritici) (Tolmay, 2001, p.240). All these biotic stressors are harmful to crops and it is vital, therefore, to improve the tolerance of important crops to such negative factors. Injured plants are underproductive and thus, farmers do not produce quality products.

Food Safety

Food produced from animals and crops should be safe for human consumption. Technology has been harnessed to curb such problems as food poisoning or simply to improve the nutrition of food (Gebhard & Smalla, 1998). This issue is quite disputable now since agricultural technologies may lead to some long-term impacts on human health or the environment which is insufficiently researched. Thus, people should be aware of the techniques used during the production of goods they buy.

Environmental Impact

An objective of agricultural technology is the introduction of some measures for the necessary environmental protection (Green & Allison, 1994). It’s anticipated to mitigate external expenses; mainly the cost of pesticides and fertilizers. Biotechnology continues research to improve the productivity of crops to decrease the excessive use of land and water, to reduce environmental impact. Scientists also work on the improvement of crops resistance to negative influences of the environment.

The Basic Biological Principles used in the Development of the Technology

As different methods used in agriculture can improve the resistance to stresses, these methods should be used in order to analyze the effects of breeding and transformations performed with DNA of plants; for instance, “next-generation sequencing (NGS) technologies are able to generate DNA sequence data inexpensively and at a rate that is several orders of magnitude faster than that of traditional technologies” (Varshney et al., 2009, p.522). Agricultural technology is closely connected to and based upon basic biological principles, such as inheritance, variety, evolution, competition and survival (Blinks, 2009, p.26).

In this respect, all these biological principles should be taken into account in the process of growing tissue cultures and other transformations. Inheritance is taken into account while creating new breeds. This essential biological law is a background for genetics and this science is highly used in agriculture today. So, molecular marker-assisted breeding, gene pyramiding assisted by MAS, tissue culture, somaclonal variation and in vitro mutagenesis, in vitro selection, double haploids and wide hybridization, and genetic transformation are some of biotechnological methods and their steps as reported by Dita et al. (2006, pp.4-10).

Scientists single out genes which are responsible for a desired feature and transfer them to other species. For instance, a British laboratory isolated a gene out of the rat’s liver that could be put into canola to reduce the level of saturated fats. However, an alternative decision was made to try to transfer a gene of a white spruce tree into canola for the same purpose (Buia & Yeager, 2002, para. 4). The only reason for not transmitting the genes of rat’s liver to the plan was the expected reaction of the public.

So, it can be so that plants and legumes are the first targets of researchers because an unmanageable situation can spread various plants, as reported by Buia & Yeager (2002, para. 11), in the areas not typical of their natural habitation, due to mutation and their organisms and an acquired ability to resist certain biotic and abiotic factors.

One of the very important biological principles used in agricultural technology is the principle of competition. It is essential knowledge in crop production since scientists understand that it is necessary to create competitive species which will be able to survive and have high productivity. This principle is taken into account when developing new species. For instance, scientists take weeds that are highly resistant to various stressors and transfer certain genes responsible for these particular features into useful crops. However, genes for herbicide resistance can ‘escape’ from crops into parental wild weeds (the possibility exists for canola in Europe) and possibly cause new weeds (Nath, 1999, p.352) that can be rather problematic for the agricultural sector as well as for biologists.

The Use of the Technology

Plant Breeding

Several techniques responsible for making better plant characteristics are available. However, some of these techniques take a lot of time to bring about the desired effect. Examples of these techniques include grafting, cross-pollination, and cross-breeding. However, biotechnology techniques have been invented and have substituted the aforementioned techniques to make better plant characteristics. The techniques permit precise variations to be obtained at a much more rapid rate.

Moreover, some of the concepts of tissue culture can be actively used in plant breeding programs (Dita et al., 2006, p.7). So, the first step in the process of plant breeding is to choose the plan for crossing and choose a wild relative with a beneficial gene that can be transmitted into the initial species after a few generations of selection. Thus, the final offspring is the desired organism that has the features of the initial one and is resistant to some stressors because it also has a gene of the wild relative.

Watermelon crops, as reported by Compton et al. (2004, p.236) gained resistance only to some stressors after plant breeding procedure whereas genetic transformation improved its traits to the extent of making a biotic and abiotic resistant culture. This shows that sometimes genetic transformation can be more effective than simple plant breeding.

Nutrient Supplement

In many third-world nations, there is a large problem with undernourishment. A great number of people do not receive the nutrient necessary for good health. Scientists are therefore interested in developing species of basic crops that can deliver increased nutrition to these people. One successful invention in this field is the creation of golden rice. The golden rice has beta-carotene which generates vitamin A inside human bodies (Saxena, et al., 1999).

Abiotic Stress Resistance

Abiotic stress resistant crops have been produced, with an aim to improve resistance against such factors as drought, salinity, and temperature extremes (Kling, 1996, p.180). To achieve drought tolerance, some plants species have been obtained by regulating the transcription process (David et al., 2010, p.84). Many researchers have shown that it is possible to obtain specific genes of some drought tolerant plants and improve the drought resistance of other species by transferring to them such genes. Scientists have also found that it is possible to alter genes or molecules to improve the drought resistance of these lines. In fact, a lot of work is done in this field and some remarkable results have already been achieved.

For instance, the lentil is very vulnerable to cold temperatures and it was decided to make it cold-resistant with the help of the germplasm that appears to be tolerant to cold (Muehlbauer et al., 2006, p.150). The germplasm was evolved from germs that are cold-resistant. The germplasm is a part of a germ that contains hereditary materials such as genes that are responsible for cold-resistance. The Millennium Project’s Hunger Task Force states that the development of drought-resistant maize will contribute to solving the problem of famine in Africa and Asia (Oakley & Momsen, 2005).

As reported by Dita et al. (2006, p.10), “Although transgenic plants are yet to be examined for salt-tolerance in the field, the recent genetic advances suggest there are good prospects for developing transgenic legumes with enhanced salt tolerance”; besides, the problem of salt-tolerance can be solved with the help of salt-tolerant genes contained in tomatoes. Moreover, the process of engineering of genes for osmolyte biosynthesis shows that “With advances in enzyme purification and plant molecular genetics, the role of osmolytes in stress resistance has been strengthened by the performance of transgenic plants overexpressing or expressing genes related to osmolyte biosynthesis under stresses” (Zhang et al., 2000, p.108). thus, many transgenic plants demonstrate high resistance to salt overproducing a certain osmolyte.

The Negative Effects of the Technology

Although biotechnology has helped to improve the stress resistance of agricultural crops, there are certainly some negative impacts that must be considered.

Imprecise Technology

Genetic engineers may successfully transfer genes from one organism to the other (Harding, 1996). However, this process is associated with a number of concerns. Such processes may interrupt the normal performance of other genes which can be vital for the organisms’ wellbeing (Bergelson, 1998, p.25). Furthermore, genetic engineers aren’t able to conduct DNA surgeries which completely avoid mutations. These mutations are cable of creating severe damage to the environment. Moreover, such mutations may negatively affect the health of human beings (Mikkelson et al., 1996). It is possible to illustrate such negative outcomes by the development of allergy in people to some components present in genetically modified organisms (GMO).

For instance, when soybeans were altered by a gene taken from the Brazil nut, scientists reported many cases of allergic reactions which appeared in people who had never had allergic reactions to soybeans before (Nordlee et al., 1996). Genetic modification may cause the opposite effect to the desired result. For example, genetically modified tobacco plants which were created to reduce toxins in these plants, proved to be even more toxic since they generated octadecatetraenic acid (Reddy & Thomas, 1996).

No Long-Term Safety Testing

Admittedly, genetic engineering utilises materials from organisms which aren’t parts of normal human food provision. These actions could lead to serious negative impacts on humans (Wostemayer et al., 1997). Such distortion of human food provision may, first of all, lead to various diseases since human organism will not be accustomed to new kinds of products. Moreover, the introduction of new products for human consumption could also lead to possible mutations. These would not be revealed at once, but would have long-term development. At any rate, further surveys are necessary in this field (Wostemayer et al., 1997).

Antibiotic Resistant Bacteria

Antibiotic resistance genes are used in staining genetically engineered seeds (Coghlan, 1999). The outcome is that genetically engineered plants have antibiotic resistant genes. The main undesirable consequence with this is that the health of human beings may be impacted negatively (Coghlan, 1999). First of all, such genes can be transferred in natural way to pathogenic bacteria which may cause severe health problems in humans, e.g. such serious diseases as tuberculosis. There is concern over antibiotic resistant genes contributing to the development of resistance in numerous bacteria which affect humans (Eady, et al., 1995). Without proper labelling, people would have no opportunity to make a choice, and when they purchased products containing GMO they would not be aware of possible risks.

Ecosystem might be damaged

There is concern the ecosystem may be impacted negatively (Metz et al., 1997) by genetically modified foods. For instance, the development of genetically modified plants with pest resistance leads to diminishing numbers of species of insects which are a part of the food chain. The distortion of the chain can result in the disappearance of other species such as birds or small mammals (Metz et al., 1997). Furthermore, new species of plants can overtake existing ones. It is still unclear whether the new plants can be safely produced. Perhaps, in future it will turn out that these new species are harmful for the environment and there will be a need to stop producing these species. However, until that time, original plants could be lost, totally supplanted by new ones.

Gene Contamination May Not Be Erased

If genetically engineered organisms, such as bacteria and viruses, are introduced, an undesirable consequence may occur. The consequence is that it may be impossible to recall those (Field & Solie, 2007). Not knowing whether these organisms are going to be harmful, therefore, is of concern. One of the possible threats of these organisms is the development of diseases which have not yet been encountered, and for which there are not yet any cures or prevention. These genetically engineered organisms may also cause mutations in existing plants and animals, leading to unpredictable consequences (Field & Solie, 2007, p. 342).

Conclusion

In conclusion, it is possible to say that modern agricultural technology development which is based on the major biological principles enables scientists to improve on many crop production factors, including improvements in stress resistance. Nevertheless, further research is necessary in the development of agricultural technology since there are many negative impacts to be considered, including a lack of safety testing and negative environmental impacts. Care should be taken in addressing the concerns of the public in regards to growing and consuming these genetically modified foods.

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