Scieniists perfecting protein-rich potato

SCIENTISTS have enhanced the nutritional value of the potato by inserting a synthetic gene into the plant and are now considering how to use genetic engineering to provide the plant with resistance to pests and disease. The International Potato Centre (CIP) in Peru collaborated with Louisiana State University to produce the synthetic protein rich in certain amino acids. Although the potato has a high protein content, it is deficient in amino acids such as lysine and methionine.

More research will have to be done before a modified potato with superior nutritional value is available forhuman consumption. This !vould be of importance in developing countries, where most people depend on a single source for plant proteins. CIP has initiated research. projects in Italy to engineer resistance in the potato to bacterial wilt and soft rot (Biotechnology and Development Monitor, No 12).

Besides inserting genes to make potatoes protein-rich, research in the West is concentrating on modifying the starch content and the sugar- starch balance. These applications are primarily aimed at industries making potato starch products such as French fries and chips.
High cost of production Several factors come in the way of improving potatoes using conventional techniques. The cost of seed tubers is high and supplies are linoted. The large volume of seed tubers that has to be produced. harvested, handled, stored and desprouted makes production expensive. Farmers also have to invest in fer. tilisers and pesticides to boost yield and protect the plant. In addition, storage, transportation and processing make the potato vulnerable to, high temperatures, bacteria, fungi and insects.

For genetic engineering studies, the potato, has some advantages over other crops. It is easily manipulated in tissue culture and is susceptible to commonly used gene vector systems. Besides improving quality, genetic engineering can play a role in the development of potatoes that are better resistant to pests, diseases and herbicides.

Potato diseases are caused, among others, by bacteria, fungi and viruses. Research to engineer genetic resistance to fungal and bacterial diseases is still in the early stages. Among the options being studied are antibacterial, insect-derived genes and genes that break down fungi. The most damaging diseases are the fungi-caused late blight and early blight. Bacterial diseases are the wilt (brown rot), soft and blackleg.

The least expensive and most effective, long-term way to control viral diseases is to develop resistance to viruses. Several countries are conducting field tests on transgenic potatoes that are immune to various viruses. The resistance has been obtained by introducing protein coats of the Virus in the plant, but reports say naturally occurring genes offer far superior resistance. Another technique being tried is molecular breeding.
Pest resistance Insects harmful to potatoes are aphids, Colorado potato beetles, potato tuber worms and potato tuber moths. Aphids do not cause any direct damage but help to spread viruses. Transgenic potatoes that resist moths and beetles are being field-tested in the Netherlands, Belgium and USA.

Potato crops are also vulnerable to chemicals sprayed to control weeds. The development of herbicide resistance was one of the first commercial applications of genetic engineering. This was mainly due to financial support from agro-chemical companies. Herbicide resistant potatoes have been developed by a Belgian firm and are expected to hit the market soon.

With genetic engineering to improve potatoes acquiring such a prominent role, there is some scepticism among scientists. For herbicide resistance, the scientists contend there is no guarantee it will be obtained only for environmentally safe herbicides. They also fear the amount of herbicides sprayed may go up and offset their positive effects.

If gene insertion becomes the primary mode of improving potatoes, it may lead to negligence of conventional germplasm development. Scientists say genetic engineering research should also be accompanied by risk assessment studies that focus on crop characteristics and transgenic: traits.

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