Begegnungen
Schriftenreihe des Europa Institutes Budapest, Band 26:123–132.

ZOLTÁN BEDŐ

The Development of Agrarian Technologies and Genetically Modified Plants

The Advance of Genetically Modified Plants in Agriculture

The aim of the improvement of agricultural plants has always been the increase of their genetic diversity and the consequent utilization of new plant species. With the emergence of gene technologies and the possibilities of DNA manipulation, new dimensions have been created for plant improvements. These include the following:

– the determination of the complete sequence of genomes;

– the definition, isolation, and application of important specific genes for agricultural production, with the use of micro-array technologies;

– the definition and assembly of DNA-collections and the establishment of DNA banks;

– the inducement and creation of genetic diversity by the injection of alien genes or blocks of genes into agricultural plants.

During the past two decades, fundamental changes have occurred in plant genetics and improvements, as the result of DNA researches; within these processes a special role was assumed by transformation technologies that developed as one of the areas of molecular plant-improvements. At the arrival of the new millennium, every third hectare of soybeans, every seventh of cotton, every ninth of colza, and similar ratios of corn, had been produced in the world through genetic modification. This was the result of the “green revolution,” that, in the course of the second half of the 20^th century, reduced starvation [in certain regions of the world] through increasing plant productivities and intensive, industrial-type production of foodstuff. However, new ways and means have become increasingly necessary, since agricultural growth had apparently reached its maximum in the 1990’s in the developed countries, and the worldwide growth of the production of cereal crops had also slowed down.

It has become necessary to re-think conceptions in agriculture everywhere, providing for the following;

1. priorities for sustainability;

2. maintenance of ecological balances;

3. increase in the safety of foodstuff and promotion and improvement of healthy consumption.

All these requirements represent new challenges for the further improvement of plants. The needed changes cannot, in all probability, be achieved through the traditional methods of plant improvement. Therefore, the aim of molecular improvement is to bring about favourable changes by the application of gene technologies that cannot be achieved by traditional methods, or that could be only partially, and to a lesser extent, be realized by the latter. Through the genetic transformation of plants, their agricultural productivity, their efficacy and safety, can all be increased and, as a consequence, the variety of their usefulness can also be multiplied.

Molecular improvement includes the application of methods of plant transformation; this can be an important means in the future for the creation of a multifunctional agriculture. In such a process, agrarian production includes the preservation of the balances of natural ecology, the development of the countryside, and the promotion of healthy consumption of foodstuff. These factors would all have to be considered as priorities. Molecular improvement, using transformation technology, therefore, may be useful not only in the creation of intensive-, (high input) or precision plant-production technologies, but also in extensive (low-input) processes. The goals of complex plant improvements are the combination of molecular improvements and the application of traditional methods, usable at production under various conditions, and through them the creation of new plant varieties. Such tasks that must be completed (among others) are as follows:

1. the reduction of pesticide use in ecologically sensitive regions; for instance, improvement of types that are herbicide resistant, resistant to virus and bacterial infection, and also resistant to pests;

2. improvement of the stability of production, the improvement of cold-, drought-, and alkaline resistant genotypes;

3. production of foodstuffs promoting healthy consumption, including the increase of vitamin contents, the improvement of the production of essential amino-acids;

4. improvements in living standard, including the production of macro-molecules in medicine through bio-farming, and the reduction of allergens.

The technological improvement of the so-called first-generation trans-genetic plants had as its goal the increase of efficiency and the reduction of the damage caused to the agricultural environment. This was proved by the survey conducted by the USDA in 1999, according to which the production increase of corn and cotton, created by the use of Bt genes, and the so-called “roundup ready” soybeans came only to 4.4-10 %; however, at the same time, the application of herbicides and insecticides decreased by 22-90 % in comparison with traditional technologies. All this proved advantageous for the protection of the environment.

Transformation-technology and the Integrated Improvement of Plants

The significance of gene-technology is that it is part of the creation of new plant species. From the point of view of plant improvement, it is necessary for the production of transgenic varieties that

1. a gene or a section of genes be isolated for the purpose of transformation;

2. have a homozygote plant or genome available that had already been improved through traditional methods;

3. the preparation of a protocol for the transformation by using an applicable promoter for the production of the transformed plant;

4. the creation of a valuable breeding stock which will eventually result in the emergence of improved plant.

The production of transformed plants is not the same as the creation of a transgenic variety. This is the reason for the necessity of the integration of traditional- and molecular- plant improvement processes, because before molecular improvements could begin, first we must create agriculturally valuable homozygote genotypes that can be modified later through the infusion of a gene or group of genes by gene technology. After the transformation of the selected genotype that is improved through a traditional method, we will select a transgenic plant, also improved through traditional methods of selection. This will have;

1. stable genomes and these are inherited by later generations; corresponds to internationally required legal norms, introduced by the international association for the protection of varieties (UPOV);

2. stability of the alien gene, and useful in agriculture as a new, transgenic variety;

3. the biology of its flowering must be stable and its seeds must be available to be produced economically;

4. it must be produced safely without risk, in a given agricultural region;

5. in comparison with the donor species, the injection of the gene should bring about advantages for the producers and better value for consumers.

Molecular improvements contribute to the spread of new technologies in agriculture. It is possible that each laboratory will produce thousands of new genotypes or even more in the future, but the number of useful plant varieties will undoubtedly be much less numerous. Transformed plants that are valuable and answer the requirements of further improvement, will have less useful characteristics that are favourable for economic requirements. The phases of selection seem to prove that only transgenic plants that are useful from every point of view, will be introduced into actual production.

Researchers dedicated to the successful improvement of plants will be able to employ the results of transformation technologies only if their products contribute to the tasks whose fulfilment are expected by society.

To achieve such results, useful technologies that can be routinely and safely used must be created. At the present time, there are important differences in the application of various technologies employable for the improvement of various cereal species. While the transformation of rice can easily be accomplished, the improvement of regular wheat and durum wheat is difficult at the present time. It is therefore extremely important to create and apply a system of transformation independently of genotypes for the purpose of their improvement.

A direct method employed for the improvement of transgenic cereal plants is to use them directly as a goal of improvement. This is a practical method, even if the species in question is easily transformable. (Not all species of cereals can be transformed equally well and be used for improvement.) In a case of heavy dependence on one particular genotype – as it certainly is the case with common wheat – we suggest the use of the best transformable genotype; in turn, it can be crossbred for the introduction of a new gene to achieve an agriculturally important variety.

The success of applied transformation technology is also dependent on other factors. The technology will be optimally successful if its result is a stable transformation – through the introduction of a gene – that will not impact on the agricultural characteristics of the other genomes. In the case of cereals, there are two gene transformation methods currently in use:

1. Gene injection techniques (cell- or tissue-electroporation, methods of micro-injection, gene-inclusion by a gene-cannon, etc.) The last of these is the most widely used.

2. Transformation through Agrobacterium tumefaciens. This method is currently in an experimental stage, used for the routine transformation of common wheat in most laboratories, and it promises to be a simpler, more effective technology.

One condition of successful plant improvement is the effective injection of the alien gene in the appropriate tissue of a plant. However, in most cases, only accidental success can be expected because the places of integration are randomly distributed. It is possible that the receiving genome (DNA) integrates with the alien gene only in the presence of partial, short homologies; however, at the present time, we do not have a complete understanding of this. Apparently, a process of repairs is taking place at the point of the meeting place of the alien and the local DNA.

Attention must be paid to the possible or real risks that the transgenic technology may represent for the environment. This includes the “marker” for the selection of herbicides or antibiotics. Although we do not have as yet scientifically supported evidence, the potential dangers – including concerns formulated by certain segments of public opinion – their application must be avoided. The solution is being offered by several other techniques, including;

1. excluding selective marker-genes through a natural process;

2. the application of technologies free of marker-genes; the application of positive selection of markers (for instance, the mannoze-system.)

An organic part of the technology is a tissue culture process, applied in order to regenerate the transformed plants. The evolution of the tissue culture method has a long history; researches had begun long before the beginnings of transformation research. The use of an effective system of regeneration could be varied according to plant species. The process used for various cereal species requires an appropriately experienced researcher. The time and method used for transformation are largely determined by the selection of the system of transformation, the choice of whether diploid- or haploid-level cells are being used at its beginning. Following transformation that had started with somatic cells, there will be need for the application of a selection method that will help the creation of transgenic, homozygote genotypes. The application of a system of regeneration, starting with a protocol of haploid cells, that will raise homozygote transgenic plants after re-diplodization, is a simpler method. Time and expenses can be saved by this method.

A problem exists (during the application of various tissue culture practices) by the genotype dependence of various plant variety. One indirect solution for this problem is the use of model plant species that are easily transformable and can be regenerated. The gene transformed in a model variety that can be re-transplanted in other variety useful for agriculture may be accomplished through the traditional method of re-crossing it; however, this increases the time for the development of a transgenic type.

The promoter used for the improvement of plants significantly influences the transformation. This is especially important for cereal species because particular promoters have less impact on them than others. The promoter could be important for the stability of the injected gene, for the full development of desired agricultural characteristics. Experts working for improvement must consider environmental risks related to the use of the promoter, even if the risks represent only possible problems, because they may influence the practical use of the species. For this reason it is important to consider the choice of applying a constitutive, a selective, or an inductive promoter. All these promoters have their own characteristics; however, potential dangers created by plants used by the producers must also be considered. The choice of a promoter may also be influenced by the possible existence of intellectual property rights that could make their purchase problematical.

A gene-transformed plant created in a laboratory may not possess all expected qualities; it may have to go through other selective processes before it can be used for agriculture. One of the most important requirements is the presence of stable transplanted genes in successive generations. The selection serves the purpose of producing homozygote transgenic genotypes in the following generations, when we are creating lines that have stable expressive trans-genes. During continuous checking of the trans-gene’s presence, we must be satisfied that the trans-gene

1. can be determined to exist in appropriate plant tissues and its influence in the appropriate stage of the plant’s growth can be observed;

2. it induces only the required characteristics;

3. it does not negatively influence other agricultural characteristics.

Continuing the selection process during several generations, we may discover not only the stability of the transmitted genes, but also the possibility of mutations, and we may also sort out the so-called “gene silencing” effects. The latter may prevent the practical application of the transgenic variety. As for the undesirable consequences caused by mutation, the negative influences they possibly produce may be eliminated by the application of traditional cross-breeding methods. Therefore, the transitional gene will be present in a stable condition in the new generations. In examining the succeeding generations of the lines of transgenic plants, we must be convinced not only of the stability of the transmitted gene – in order for the plant to be useful as a new species – but we must examine

1. every one of its agriculturally useful characteristics in comparison with the original species that had not been transformed ;

2. its ability to assimilate to various agro-ecological circumstances;

3. the ecological risks of its production;

4. the safety and economy of the production of its seeds for planting that may influence the competitiveness of the species.

Arguments For and Against Genetically Modified Plants

The technology for future plant production-methods advances along several avenues. Of these, the so-called “high-yield farming” (or precisions technologies for production) provides one possibility. One of the basic elements of high input technology agriculture may be the use of transgenic plants. Through this technology

1. the average yield and quality of production may be increased and as a consequence,

2. the size of land used for agriculture may be reduced, and

3. the remaining lands may be returned to their natural conditions,

4. in the case of lands worked by modern methods, the danger of environmental damage will be reduced.

However, environmentalists, together with a sizeable segment of public opinion in the European countries, are sceptical about the utility of producing new plant varieties by transformation methods, and they are worried about possible risks for the environment. They fear the wide spread use of transformed plants. This is the reason for wide-ranging support for so-called “extensive” technologies, — free of all chemicals — and for the organic production of plants, in which plants are produced by traditional methods, or through organic improvement of plant varieties. They support methods for plant production for sustainable development.

In our opinion, a place and role can be found for every technological system within a multi-functional agriculture. We consider complementary functions more important than confrontational approaches. Genetically modified plant species may indeed serve environmentally safe production, but it is also true that they may include some risk factors. For instance, living organisms in the environment may be directly or indirectly exposed, and they may contribute to the creation of new genotypes of weeds. In the presence of related wild species, they might also easily cross-breed and contribute to the emergence of unfavourable environmental conditions and change biodiversity. In order to avoid such a possibility in Europe, a directive was introduced for genetically modified systems (GMO-s) in 1992, entitled 90/220/EEC. The OECD (Organization for Economic Co-operation and Development) declared the principle of substantial equivalence, according to which gene-modified products must be comparable to the original — or correspondingly close-standing — non-modified products. The generic plant used as the basis of comparison is considered to be a standard, environmentally safe product. In Hungary, a law enacted in 1998 to regulate activities for gene-modification was itself modified by Parliament in 2002.

During the production of seeds by the gene-modified plants they must be examined in order to discover whether the injected (or infused) alien gene could be accidentally transferred to other non-gene modified, or other species that are found in the environment. Theoretically, the spread of the alien gene could take several forms; in the first instance, there is a sexual method of transmission.

We have relatively little information about the sexually transmitted trans-genes. The person doing the improvement of specific plants must consider public opinion while formulating plans for his research. This is especially important for European researchers, because here we find the widest divergence in consumer behaviour. As a consequence, European researchers have certain disadvantages in the application of gene-modification technology in comparison with researchers working in other regions of the globe. According to a survey conducted in 2000, the European researchers are making great efforts to overcome their disadvantages. Of 99 European companies currently working on plant-improvement projects, (surveyed in 1999), 33% worked on research in gene-technologies, besides studying traditional improvement methods. They were planning to increase this number to 49 % by 2002. Further 31 % of the companies in question were planning to employ marker-technologies and the “sequenation” of genes in contrast to 23% in 1999.

Every four out of five European companies conducting improvement research, employ molecular-methods in addition to traditional approaches, but this does not mean that they produce gene-modified, trans-genetic plant species every time. Their activities are mostly based on the practical application of scientific results of genome-research.

However, direct and indirect dangers and obstacles to progress continue to exist. Among others, they include;

1. the fact that agricultural production in Europe is going through a difficult period; it is comparatively expensive and over-bureaucratized;

2. capital needs of plant improvement continue to increase rapidly, competition is fierce, concentration has been increasing, the number of improvement-programs is declining, and the consequences might lead to the decrease of genetic diversity;

3. in addition to the increase of expenses for plant-improvement research, further increases will probably occur, because of the introduction of ever stricter safety regulations;

4. as a result of the practical application of improvements, appropriate profits are gained by seed-producers through raising hybrid plants. Consequently, the improvement and production of self-pollinating plant species, raised on medium- and small plots, (the production of monocultures) is continuing; further, the increase of the number of patented plants (IPR) restricts genetic diversity and this might bring about potential dangers of genetic vulnerability in the future;

5. the accessibility of gene-banks continues to be restricted world-wide, as well as those of genetic resources, the life-blood of agriculture; the consequences may be natural catastrophes if epidemics of plant diseases would occur;

6. classical methods of plant-improvements had been restricted in various regions of the globe, that traditionally produced new gene-types necessary for molecular improvement, and provided starting points for improved plant species for the future; state support for such activities have also been drastically reduced (this is especially true in Europe);

7. negative views of gene-modification in Europe continue to obstruct the potential for the exploitation of gene-modified plants, and applications of gene-technology for the improvement of plant species;

8. there is no uniform, required standardization for the results of gene-technology, and no rules exist for their practical use.

These problems directly influence Hungarian projects of plant improvement. Besides the difficulties of a transitional period, we must also be prepared for Europe-wide regulations and challenges. Therefore, we need a complex research program in which plant-improvement researchers, familiar with gene-technology, could work conjointly with molecular geneticists who are also familiar with the thinking of the traditional plant breeders.