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Is Genetically Modified Food A Poison?

By Father Leo D’Souza,S. J.,
Promotio Lustitiae,
Social Justice Secretariat,
Society of Jesus (Rome). 2003

(From Prakash: Father Leo is a rare individual - the only Jesuit priest that I know who is also a plant biotechnologist. Trained in Germany, he heads a lab at a small college in India that employs biotechnology in developing solutions to local problems in agriculture. He has also has trained over three decades many students and scholars. A celibate priest who understands the virtues of modern gene transfer that obviates the hassles of sexual crossing in plants.)

I am writing this response as a Jesuit plant breeder and a Jesuit Biotechnologist. Plant breeding is in principle modifying the existing genome of plants using various techniques. Genes have been modified by nature, plant breeders and, in recent years, by transgenic technology.

Genetic modification in nature

In nature genetic modification occurs due to abnormal crosses i.e. crosses between plants belonging to different species or even genera, which normally do not mate with one another. Hard wheat and bread wheat are the result of introduction of genes of a wild grass, Aegilops, into primitive wheat. Modern maize is the product of a cross between primitive maize with Tripsacum a wild grass. Both wheat and maize are therefore essentially genetically modified organisms.

Genetic modification in nature has also occurred as a result of various stresses such as temperature, chemicals and radiations. This is responsible for the vast divergent genetic pool that is presently available in nature.

Genetic modification by classical plant breeders

Classical plant breeders have used the same techniques to create new plants or to transfer a desired gene from a wild relative to a cultivated plant. Triticale and Secalotricum are crosses between wheat and rye and have been accepted and cultivated in spite of being genetically modified organisms. Genes for disease resistance, for dwarf or tall varieties, have been inserted into cultivated plants. We would not have many of our present cultivars without modifications being introduced into their genetic make up. The dwarf varieties of rice and wheat that ushered in the Green Revolution were the result of mixing and modifying the genomes of a wide variety of these plants. The process of identifying and selecting the plants with the desired character however is very laborious and time-consuming. As in nature, plant breeders have created a wider gene pool by inducing mutations using chemicals and radiation.

Genetic modification using molecular techniques

Molecular biologists have helped to refine the techniques used by classical plant breeders. It is no longer necessary to mate two individuals and to limit the mating to plants, which are able to cross with one another. Specific genes can be identified, isolated and multiplied by molecular methods and can be transferred to another organism with the aid of tissue culture techniques. The problem however is to identify and select plants which have the new gene. For this, the desired gene is tagged on to a marker gene which can be easily, that is, visually or chemically detected. The first marker gene which biotechnologists hit upon was a gene inducing herbicide resistance. Plants, which are putatively transformed, were grown in a medium containing the herbicide. Only such plants which had the Herbicide Resistance Gene (HRG), and with it the desired gene, survived.

This technique unfortunately has some drawbacks. It is possible that the plants tagged with the HRG will eventually dominate, resulting in a herbicide resistant race. A discovery that genes can be transferred laterally and can be absorbed by organisms from the soil or water adds to the fear that these genes may be transferred to other cultivars. However, scientists are aware of the problem and are now using alternate marker genes like the green fluorescent protein gene. Techniques have also been developed to withdraw the marker gene once its function is over.

Another fear is that genes, which are introduced from other organisms, could induce allergies in persons who use these as food. The basis of this fear is a gene from a Brazilian nut, which enhances protein production but causes allergy in some persons. People who were allergic to the nut fell sick when they ate products from plants transformed with this gene. That is why it is necessary to have a warning label while marketing food containing foreign genes. This certainly does not mean that all people who eat food with this gene will be sick.

A similar fear is that if a gene produces a substance that is toxic to pests, as in the case of the Bt gene from Bacterium thuringensis, this substance could also be a poison for people who eat the product of the plants modified with that gene. This fear is the reason why many people reject genetically modified maize which has the Bt gene. The residues of this bacterial spray cannot be fully eliminated and so there is a chance it might get into the food chain. But no one has yet protested against its use as a spray on cultivated plants. In recent years the Bt gene has been spliced and built into various plants. Insect larvae of some genera die when they feed on these plants. The gene is however highly specific in its action and requires for its expression a high pH environment18 which is not available in humans. Studies made so far do not indicate that there is any toxic effect on human beings when they eat food with a Bt gene, whether sprayed on the plants or built into them.

Our Experience and Experiments In India the only crop allowed to be cultivated is the Bt cotton. Our visits to the farmers and interaction with them show that these farmers are happy with the Bt cotton as it reduces the costs of spraying the crop against the bollworm. Many farmers in their eagerness to grow Bt cotton have bought spurious seeds from fake seed companies and the poor cotton crop of this season has been used as a cudgel with which Bt opponents can browbeat the Bt proponents. However the Bt gene is only an insecticide and, like all other insecticides, is not directly responsible for the quality or yield factors of any crop. The overall poor cotton crop is a result of the prolonged drought and, to some extent, the use of spurious seeds. Compared to genuine Bt cotton, plants without the Bt gene or from spurious seeds have shown a much lower yield due to drought and insect attacks

In our Laboratory we are working on the transformation of three species of plants. Cashew is a commercially useful plant fetching much-needed foreign exchange for the country. Besides, it provides work for a large number of rural women. The cashew trees grown at present are low yielding, the yield is further reduced due to pests, and the raw nuts produced are not enough to meet the market demand and to provide regular work for women. We have established a protocol for large-scale multiplication of elite, high- yielding cashew trees using tissue culture techniques. We are now trying to introduce an insect resistance gene into the cashew plant, for we find that at present the plantations need to be frequently sprayed with heavy doses of insecticides. Spraying brings down the insect attack to some extent but constitutes a health hazard to people in villages around the plantations. Cases of malformation of neonates, deformities and various diseases in grown ups have been reported. An insect resistance gene built into the plant will not only control insect attacks more efficiently but will also help to avoid risks to the health of the people.

Chilli, Capsicum annuum, a condiment used by the people of this region, is attacked by pests that bring the yield down considerably. Heavy doses of pesticides are needed to prevent losses. Some pesticide residues remain on the pods even after they have been washed and enter the food chain of humans. We are currently engaged in experiments to transform the Chilli plants by introducing pesticide resistance genes that will prevent loss of the crop as well as contamination of human food through pesticide residues.

Ragi, Eleusine coracana, a coarse grain, cultivated and eaten by the very poor people of the state of Karnataka, is attacked by several insects that destroy the crop, causing great losses to the poor farmers. We are studying the possibility of inserting an insect resistance gene into Ragi to control losses arising from insect attack.

My team members and I are convinced that our work is economically and environmentally useful. It will not only help prevent crop losses due to insect attacks, but will also minimize the use of pesticides, promoting thereby a safer environment.


Introduction of genetically modified food has raised a number of fears, some genuine and some irrational. Human fears, whether genuine or irrational, have to be attended to. New pharmaceutical products are tested for their efficacy as well as their side effects before being marketed. Any new variety of plants is tested for its qualities before being released. So too, genetically modified plants, before they are approved for cultivation, need to be tested for their quality, and particularly to ascertain whether they are in any way toxic to humans. Proper precautions and controls have to be exercised before they are marketed. It is certainly self-defeating if we wholly ban all genetically modified organisms on account of certain problems and fears.

The author did his doctoral studies in plant breeding at the Max-Planck Institute for Plant Breeding in Cologne, Germany. He is currently doing tissue culture and molecular studies of some important crops of India. The paper has been written in consultation with his team, Dr Smitha Hegde, Dr A C Augustine, M Anuradha and Sashikiran Nivas.

--- Leo D’Souza, S.J., Laboratory of Applied Biology (Dr Küppers Biotech Unit), St. Aloysius College Post Box 720, Mangalore 575 003 INDIA<leodsouza@hotmail.com>