Genetic modification

Introduction

The genetic modification of plants offers some interesting prospects for the gardener. The Society aims to take a balanced stance on the subject, recognising the potential of these techniques, as well as some possible drawbacks. The RHS is not involved in the production of genetically modified (GM) material, nor in research into any potential problems of genetic modification. Some techniques which are used by the RHS for plant identification and disease diagnosis involve gene studies, where conventional techniques cannot distinguish between cultivars or disease strains.

Genetic modification for plant improvement

Genetic modification is an extension of conventional plant breeding in that it involves the transfer of genetic material. During plant breeding characteristics of plants are selected and allowed to combine to produce improved plants from their seed. The principles of genetics were first demonstrated by Mendel in garden peas. It may take generations of breeding to produce a plant with the desired attribute.

Genetic modification inserts the appropriate genes for certain characteristics directly into plant cells and cultures new plants from these cells, using a technique known as "tissue culture". Genes are inserted into the plant cells using microscopic carriers. Bacteria such as Agrobacterium tumefaciens can insert their own DNA into cells in order to multiply, which causes disease. This can be altered so that they insert the selected gene instead. Altered viruses can also be used. A further method involves coating microscopic metal pellets with the required gene sequences and firing them into the cells.

This technique makes possible new combinations of genes that were impossible to achieve by conventional methods. It is this artificial transfer of genes that raises concerns about its use.

Examples of genetic modification in crops

There is a wide range of plants which are being studied for the possibility of genetic improvement, in terms of ease of cultivation or food quality. Many are agricultural crops with a high commercial value. There is currently little emphasis on genetic modification of plants of horticultural interest. The first GM plant was herbicide resistant tobacco released in the USA in 1983.

• Field trials of herbicide resistant maize, oilseed rape and beet are in progress this season on selected sites around this country. A gene which occurs naturally in a range of plants and bacteria confers resistance to the herbicide glyphostae. The gene has been transferred to these crops, to allow them to withstand application of the herbicide. This aims to reduce the number and cost of herbicides required in their cultivation. In the USA herbicide resistant soya has been released, and is also licensed in the UK.
• In tomatoes the enzyme activity which leads to the break down of the fruit during processing has been altered, and the fruit used in tomato paste in 1996. This product has been removed from shop shelves now.
• An insecticide derived from the bacterium Bacillus thuringiensis has been inserted into maize to reduce insect damage, and licensed in Europe.
• Rose resistance to blackspot disease has been improved in research studies using a gene from rice.
• A blue carnation "Moonshadow" was developed by the Australian company Florigene Ltd. There is no gene for blue colouration in carnations, so this was incorporated from a pansy using genetic modification. It is not currently available in the UK.

Benefits and concerns

The technology of genetic modification could be used in future in many ways.

• It has been suggested that this technology could increase food production in developing countries.
• The nutritional quality of food could be improved such as vitamin A content in rice.
• It is possible that the production of vaccines could be made easier with GM plants.
• Detoxification of polluted soil is also being examined using GM organisms.

Some of the concerns about genetic modification include:

• the potential for uncontrolled transfer of genes to non-GM plants, such as in pollen transported by bees.
• Wild species in hedgerows could be lost by changes in the use of pesticides.
• It is not known whether GM foods could provoke adverse reactions in the consumer.
• Some weed species may become uncontrollable due to herbicide tolerance.

There also remain considerations about commercial issues, since the control of GM crops is by a small number of companies in the developed world. Outside this control, there has been high use of GM crops in the People's Republic of China. Ethical debates also continue on the appropriateness of this new technology.

This is a new and developing area for which the regulations are being reviewed. Due to the wide range of combinations of plants and genes that are being researched, it is not possible to say whether genetic modification is beneficial or harmful, but each combination must be reviewed on its merits. More detailed information can be found on genetic modification and RHS policy, in the RHS Conservation and Environment Guidelines leaflet .

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