Case study

DFID Research: "clean genes" open the door to new pest-resistant rice

New methods for genetic transformation avoid using unwanted marker genes.

Rice seed heads
Rice seed heads. Picture: Desmanthus4food

A “clean gene” technology has been used to breed upland varieties of rice to make them resistant to virulent pests which make them weak and unproductive.

This important scientific breakthrough has been made by scientists at the John Innes Centre in Norwich and at the University of Leeds, as part of the DFID-funded Plant Sciences Research Programme. It has important implications for farmers who cannot afford to buy the chemical treatments that destroy pests such as nematodes. Nematodes are the microscopic worms that bore into the roots of plants in order to feed, grow and lay eggs. They attack and weaken upland rice and other major staples, causing estimated losses from 1 to more than 10 million tonnes in Africa and in Asia, respectively.

Chemical treatments are available, but they are very toxic and undesirable to both people and the environment. In addition, they are too expensive for most poor farmers in the developing world.

Farmers have always tried to improve their crops through a combination of manipulation and selection, but the process takes many generations (large investments of time) and does not always work. Scientists designed an additional approach to this crop improvement with genetic techniques to improve the physical features of crops (size, flowering, etc.) as well as their performance (tolerance to drought, cold, frost and or resistance to pests etc.). But the process is not perfect.

Transgenic crops are genetically modified organisms that contain one or more genes that have been inserted artificially, either from an unrelated plant or from different species altogether. But there is a problem. Transgenes don’t often insert into plant cells, so scientists insert a second, marker gene, that is easier to detect (for example making the cell resistant to antibiotics or herbicides: by exposing the whole batch of cells to an antibiotic or herbicide, all the untransformed cells die, and only the one or two transformed cells live on and grow into transgenic plants).

The catch is that the transformed cells, and the plants that grow from them, not only contain the desired gene but also the antibiotic or herbicide-resistant gene, or whatever marker was used. The John Innes Centre ‘clean gene’ process is an improvement because it transfers only the desired trait to the rice plant, with none of the undesirable selectable marker genes.

‘Clean gene’ technology can be used for all plants that produce seeds, and has great potential for rice-growing countries in Asia and Africa. Scientists have already expressed great interest in the technology, and rice plants that are resistant to nematodes, and free of undesirable selectable marker genes will be made available to any country that requests them.

More information

See the DFID project record for Genetic transformation of rice, potato and cooking bananas for nematode resistance and this article in the New Agriculturalist: A Clean Pair of Genes.

Published 4 April 2006