RADIOISOTOPES A TOOL FOR 
AGRICULTURE SCIENCE

By Dr. S.M. ALAM, NIA, Tando Jam
Aug 12 - 18, 2002

Isotope represents a tool, which can do certain jobs better, easier, quicker, more simply, and cheaper than competitive methods. Some measurements could not be done at all without the use of isotope, as there are no alternative methods available. Isotopes are ideal tool for use in analysis, a single atom can be detected when using radioactive isotopes, as compared to chemical methods in which the detection limit of an element is enhanced a million times. Stable isotopes also can be detected with great accuracy nowadays, although not quite with the same sensitivity as radiation emitting (radioactive isotopes).

Most important, especially in biological and medical work, is that radioisotopes can be located during a biological process, the functioning of certain glands also can be checked, by first administering a small amount of a radioisotope and then following the path of this compound in the body simply by measuring the radiation from the outside. Larger sources, some 1,000,000 times stronger, which emit penetrating radiation, can be used as a portable X-ray unit to check welds in underground pipelines, such sources also are used for certain analysis especially suited for work in the field, such as in geology. Very large sources, some 1000 million times stronger than the activities used as tracers, can destroy bacteria or other spoilage organisms in food, can be used for sterilization of medical sutures or syringes or can impart specific desirable properties to some materials. They find wide application in practically all fields of science and industry.

FOOD AND AGRICULTURE: In agricultural research isotopes are a basic tool without which research in molecular biology could not be done. The main agricultural problems isotopes and radiation are helping to solve are to determine conditions necessary for optimizing fertilizer and water use efficiency, as well as biological nitrogen fixation: i) breed high performance, well adapted and disease resistant agricultural and horticultural crop varieties using radiation induced mutations; ii) eradicate or control insect pests using insects that have been radiation sterilized or genetically altered; iii) improve reproductive performance, nutritional status, and health of animals using radioimmunoassay and related techniques, as well as isotopic tracers; iv) reduce food borne diseases and extend shelf-life using radiation and reduce pollution from pesticides and agrochemicals.

CROP PRODUCTION: A good crop needs soil with adequate amounts of nutrients and moisture. Nuclear techniques are ideal tools for measuring the efficiency of fertilizer use by crops and for keeping a watch in the moisture contents. In modern agriculture, the use of fertilizers is essential to maximize crop yields, through biological process, that legumes fix nitrogen can provide high protein for human and animal consumption and also increase nitrogen in soils. The water plant Azolla, for example, can derive 80-90 per cent of its nitrogen by fixation, and is valuable in providing nitrogen to paddy rice crop, in this way obtain maximum benefits from this unique biological process, isotopes are used to find the amount of nitrogen that a plant can fix and how this can be improved. Isotope techniques are an ideal tool to distinguish nitrogen derived from the atmosphere, soil and applied fertilizer. Water is the most important limiting factor for crop production in many areas of the world. The efficient use of water in irrigation systems requires continuous monitoring of the moisture content of soil. Neutron moisture gauges are ideal instruments for this purpose and help soil physicists to make the best use of limited water resources. Through these methods, traditional irrigation methods are improved and in some cases up to 10 per cent of the water can be saved.

AGROCHEMICALS: Isotopes are ideal tools for studying the behaviour, breakdown, and residues of agrochemicals in soil, water plant, animals and their products. As a result of their use, it has been possible to devise safer ways to apply agrochemicals and safer formulations which are more effective in controlling pests of promoting growth, as well as less harmful to health and the environment.

MUTATION: For centuries, mankind tried every possible way to improve quantity and quality of crops. Natural evolution results from spontaneous mutation and selection of the fittest mutants. The rate of mutation occurrence can be multiplied by radiation treatment thereby accelerating evolution and the selection of superior crops. Over the last 50 years, a number of plant breeding programmes have included mutation induction with radiation or chemicals to breed improved crops. Physical mutagens like X-ray, gamma rays or fast neutrons are most frequently applied and their use has resulted in the highest number of improved mutant crops. The number of induced mutant derived crop varieties now exceeds 1500 worldwide with billions of dollars added to farmer's incomes annually.

i) IMPROVED LODGING RESISTANCE: The derived properties are a reduction in plant height and a stiffer stem, which can withstand rain and storm.

ii) CHANGED MATURING TIMES: Early maturing is important to escape frost, pests etc. or simply to make room in the field for other crops.

iii) INCREASED DISEASE RESISTANCE: Becoming very important in attempts to decrease the use of chemicals which are used against pests to protect the environment.

iv) INCREASED YIELDS: The yield of many crop varieties has been increased many fold after mutation breeding using nuclear techniques.

v) IMPROVED AGRONOMIC CHARACTERS: For example, more winter hardiness, greater tolerance against heat, or generally better adaptability to available soil conditions.

vi) IMPROVED SEED CHARACTERISTICS: Improvement of nutritional value (protein or oil content), backing and melting qualities, or reduction in cooking time.

Radioisotope have done remarkable work in the field of agriculture in the country. Through the use of radioisotope, the four agriculture centres of PAEC have evolved many varieties of wheat, rice, sugarcane, chickpea, etc. It has been estimated that PAEC's agriculture centres have released more than 30 genotypes of these crops, which are growing in the four provinces of the country and have contributed substantially in the agricultural development of the country.

FOOD PRESERVATION: First priorities in the world is to have enough healthy food for everybody. For thousands of years, this problem has been with us and preservation methods have evolved from the earliest days of sun drying to salting, smoking, canning, freezing, heating and the addition of chemicals. A relatively new commercial process, food irradiation has been studied more thoroughly than any other food technology. More than 40 years of research have shown conclusively that there are no adverse effects from the consumption of irradiated food.

In fact, for many foods, the preservation of food by irradiation has proved to be by far the best method. All necessary rules and regulations to irradiate certain foods have been adopted by the relevant international authorities, but there is still some public reluctance over the acceptance of such foods. In the future, food irradiation will certainly develop to be one of the great benefits for mankind, and food preservation by irradiation will be of greatest importance to food products grown in developing countries. The benefits of using irradiation, it can kill viable organisms and specific, non-spore forming, pathogenic micro-organisms such as salmonella, or it can interfere with physiological processes, for instance it can be used for sprout inhibition of potatoes or for extending the shelf life of fresh fruit. In short, irradiation of food is an alternative, and in some cases, the only methods to: i) eliminate many health risks in food; ii) enhance the quality of fresh produce; iii) improve the economy of food production and distribution; iv) reduce losses during storage or transportation and disinfest stored products such as grain, beans, dried fruit, and dried fish.

WORLDWIDE APPROVED USES OF IRRADIATED FOODS

COUNTRY

PRODUCT

Argentina

Spices, spinach, cocoa powder

Bangladesh

Potatoes, onions, dried fish, pulses, frozen seafood, frog legs

Belgium

Spices, dehydrated vegetables, deep frozen food, including sea food

Brazil

Spices, dehydrated vegetables

Canada

Spices, potatoes, onions

Chile

Spices, dehydrated vegetables, onions, potatoes, chicken

China

Potatoes, garlic, apples, spices, onions, Chinese sausage, Chinese wine

Cuba

Potatoes, onions, cocoa beans

Denmark

Spices

Finland

Spices

France

Spices, vegetable, seasonings, poultry (frozen deponed chicken)

Hungary

Spices, onions, wine cork

India

Spices, onions, potatoes

Indonesia

Spices, tuber and root crops

Israel

Spices, potatoes, onions, grains

Japan

Potatoes

Korea, Rep. of Netherlands

Garlic powder, potatoes, onions, spices, frozen products, poultry dehydrated vegetables, rice, egg powder, packaging materials

Norway

SDices

Pakistan

Potatoes, onions, garlic, spices

South Africa

Potatoes, onions, fruit, spices, meat fish, chicken processed products, vegetables

Snain

Potatoes, onions

Syria

Potatoes, onions, chicken, fruit, spices.

Thailand

Onions, fermented pork sausages, potatoes

USSR

Potatoes, onions, cereals, fresh and dried fruits and vegetables, meat and meat products, poultry, grains

USA

Spices, poultry, fruit

Yugoslavia

Spices, cereals, meat, poultry