The IAEAand the green revolutionFrom research laboratories to farmers' fields,nuclear techniques are making a difference

by Bjorn Sigurbjornsson and Leo E. LaChance

The term "green revolution" originally referredspecifically to a few high-yielding cereal varietiesdeveloped in the 1960s that, together with more use offertilizers and pesticides, started a food production revo-lution, primarily in Asia. A number of chronically fooddeficient countries suddenly became self-sufficient incereals, accumulating large reserves and eventuallybecoming net food exporters.

Looking back, it is clear that this was the beginningof an agricultural revolution that in a mere two decadesnegated the doomsayings and predictions of widespreadfood shortage of the 1970s. Many places in the worldstill have serious malnutrition, but generally speakingthis is often due to natural catastrophies, politicalfactors, and other reasons, and not from a lack of foodproduction technology. Food production has outpacedpopulation growth. The amazing progress is primarilydue to advances in plant breeding and crop husbandrybased on vastly increased inputs.

From the very beginning of this green revolution,nuclear techniques played a significant role. Theyprovided an added dimension to agricultural researchand development which in many cases proved to becrucial. Research based on the unique properties ofradioactive and stable isotopes of plant and animalnutrient elements has greatly accelerated our knowledgeof plant physiology and crop nutrition. It has providedan essential base for any progress in crop husbandry andhas added to our knowledge of animal nutrition,

Messrs. Sigurbjornsson and LaChance are the Director and DeputyDirector, respectively, of the FAO/IAEA Joint Division of Isotope andRadiation Applications of Atomic Energy for Food and AgriculturalDevelopment.

Photo above: Radiation-induced mutant of barley has short, erect,and dense spikes.

reproduction, and disease diagnosis — prerequisites forraising animal productivity.

Ionizing radiation has proved invaluable for enhanc-ing genetic variability in crop plants. It induces bothdeleterious and beneficial mutations and permits plantbreeders to utilize new genes and gene combinations toproduce crop varieties that are disease resistant, betteradapted, higher yielding.

Through the • same mechanism, ionizing radiationcauses sterility in insect pests, thereby curtailing theirreproduction, and sterilizes or kills pathogens andorganisms that cause food-borne disease and spoilage.

Thus, alone or in combination with other advancedtechnologies, the various applications of nuclear tech-nology have contributed to this revolution at every stageof the food production path — from soil, water, andseeds through plant and animal development, and theprotection of stored foods until they reach the con-sumer's table. At the same time, these tools have helpedin research to protect the environment in response to thevastly increased use of potentially har.nful chemicals.

Agency's involvement

Soon after the IAEA was founded in 1957 an agricul-tural expert was hired. He started the agriculturalprogramme by placing research contracts with some ofthe world's foremost users of radiation-induced muta-tions in plant breeding. Five years later, the firstco-ordinated research programme was organized usingisotopic tracers to help Asian rice producing countriesestablish more efficient fertilizer practices. Otherprogrammes followed, revealing better ways to placeand time fertilizer applications in wheat and maize fieldsand eventually branching into very successfulprogrammes to enhance nitrogen fixation of legumes andto improve irrigation practices through use of isotopes.

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By 1964, programmes had also been started inentomology, animal science, and food preservation. Thesupporting activities of the Seibersdorf Laboratorieswere establishing themselves as the very backbone of theAgency's agricultural programmes and, in retrospect, asthe key to the great success of these programmes indeveloping countries. (See the article on the SeibersdorfLaboratories in this edition.)

In that same year, 1964, the Agency's programmeunderwent a profound change which was to provefundamental in ensuring the effectiveness and relevanceof the programme to food and agricultural developmentworldwide. This was the agreement between the IAEAand the Food and Agriculture Organization (FAO) of theUnited Nations to establish a joint division responsiblefor all UN activities in this field. This enabled theAgency to interact directly with the agricultural researchefforts from which the green revolution sprang.

This article provides only a few examples of the addi-tional achievements of the six sections that comprise theJoint FAO/IAEA Division:

Plant breeding

The Plant Breeding and Genetics Section has deve-loped effective standardized methods of mutagen treat-ment of seeds and plant parts, as well as methods ofassessing radiation effects and isolating and testingpromising mutants. Thus, the FAO/IAEA Mutationbreeding manual has been used by plant breeders theworld over for the last 20 years and has significantlycontributed to the great success of induced mutant cropvarieties.

The unique contribution of induced mutations to thegreen revolution is their ability to repair deficiencies inthe highest yielding and best adapted varieties. The newsuperior varieties developed using induced mutations areeither used directly in farmers' fields or used in furtherbreeding programmes. As a result, induced mutations

are, for example, carried in the genotypes of many of thebest varieties of barley grown in Europe, durum wheat(pasta) grown in Italy, rice grown in California, as wellas in some of the most productive crop varieties grownthroughout the developing world. In many cases, theoriginal radiation seed treatment was carried out at theSeibersdorf Laboratories, the breeders were trained bythe Agency, and the superior varieties resulted fromwork carried out within Agency research contracts ortechnical co-operation projects. At the present time,nearly 1000 crop varieties derived from radiation-induced mutations are grown worldwide on severalmillion hectares. If all varieties with mutants in theirparentage are counted, the number reaches possibly tensof millions. The annual economic gains are measured inbillions of dollars.

Soil and water

Isotopes provide the only direct means for distin-guishing native-soil from fertilizer-derived nutrients inplants. This then makes it possible to assess howefficiently plants use an applied nutrient source in orderto recommend the best ways to increase the efficient useof costly fertilizers. In some cases, this results in theapplication of minimum amounts of fertilizer for maxi-mum plant growth.

In a co-ordinated research programme of ninedeveloping countries using fertilizer labelled withphosphorus-32 in rice soils, it was found that the place-ment of phosphate fertilizers on the surface of the soil,or worked into the surface soil, was more than twice asefficient in supplying phosphorus to plants than when itwas placed 10 centimeters deep between rice rows. Thisfinding permits a reduction in fertilizer use by more thanone-half without loss of yield.

Fertilizers labelled with the stable isotope nitrogen-15were used to demonstrate that deep placement (5-15 cen-timeters) of nitrogen fertilizers in soil gives higher

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Scene from 1977 training course in Indiasponsored by the IAEA, FAO, and SwedishInternational Development Agency, wheremutation breeding of sorghum with improveddisease resistance drew keen interest.

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uptake efficiencies than surface applications. The datafrom 13 developing countries showed an increase ofabout 32% in nitrogen uptake efficiency by plants whenthe fertilizer was placed at this depth, compared tosurface application. One participating country which fol-lowed fertilizer recommendations based on these resultsreported that US $30 million were saved in one yearfrom reduced nitrogen fertilizer applications.

Methods for using nitrogen-15 in the field todistinguish biologically fixed nitrogen in plants from thenitrogen derived from soil was developed largely bystaff of the Agency's Soil Fertility, Crop Production,and Irrigation Section and its Seibersdorf Laboratories.

Large differences have been found among grainlegume species in their abilities to fix atmospheric nitro-gen. For example, while one type of bean plant, Viciafaba, is able to satisfy about 70% or more of its nitrogenrequirement from nitrogen fixation, another type,Phaseolus, a common food grain legume, derives about30% or less from it. A co-ordinated researchprogramme was subsequently initiated to breed forhigher nitrogen fixation in Phaseolus and there are signsthat this will be possible. A slight increase in nitrogenfixed in this common grain legume would result in a sig-nificant reduction in the use of nitrogen fertilizerworldwide.

A grass pasture in Uruguay offers an example of pos-sible savings: The inclusion of white clover thereresulted in the pasture fixing about 120 kilograms nitro-gen per hectare from the atmosphere within 6 months.This is equivalent to saving about 250 kilograms of ureafertilizer per hectare worth about US $73 per hectareover 6 months.

Livestock

Most developing countries in tropical and sub-tropical regions suffer from shortage of livestockproducts, not because of any serious lack of livestock,

An essential source of protein in diets of mil-lions of people, pulses have been a focus ofthe Agency's plant breeding programmes for30 years. About 80 improved cultivars of13 different species derived from radiation;induced mutations have been given tofarmers for improved food supplies.

but because animals there are much less productive thanthose in temperate regions.

The activities of the Animal Production and HealthSection are aimed at raising animal productivity byimproving nutrition, reproductive capacity, and diagno-sis of disease in affected regions. One method advancedby the Section is the development of supplemental feed-ing strategies: Cheap local sources of crop and animalresidues (for example, maize stover,. sugar-canebagasse, fish meal, poultry manure, andalkali/ammonia-treated straw) and agro-industrial by-products (such as urea) are included in the diet.Livestock receive a more balanced input of dry matter,energy, protein, minerals, and vitamins, and so theirproductivity improves. The adequacy of the sup-plemented diet is assesed in-vitro by the use of isotopictechniques. The supplemented material — identifiedwith a radioactive marker such as ' carbon-14,phosphorus-32, iodine-125, or hydrogen-3 — is passedthrough an artificial rumen apparatus and its influenceon the rumen fermentation products, microbial, and by-pass protein is assessed before on-the-farm testing. Thisscreening of feed supplements before use in livestockfeeding trials has increased the rate at which new ormodified supplements can be tested and has dramaticallyreduced the costs.

Radioisotopes such as hydrogen-3 and iodine-125have been used to help identify and measure hormoneswhich facilitate metabolic studies in order to enhanceanimal reproduction. Isotopes have been used to developradioimmunoassay (RIA) and enzyme immunoassay(ELISA) tests that constitute some of the most effectiveroutine diagnostic procedures concerned with reproduc-tive disorders, therapeutic needs, toxicological evalua-tion, and residue studies.

The use of nuclear technology has played a signifi-cant role in the formulation and monitoring of hormonesnecessary for embryo transfer, embryo sexing, andother enhancements of the, reproductive process.

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Development of modern livestock systems in both deve-loped and developing countries has been greatly aided.

Radioisotopes and radiation are also used in animaldisease diagnosis and control. The Section has supportedthe application of radiation for production of animalvaccines. The most spectacular development has beenthe introduction of an irradiated vaccine against lung-worm in cattle, a seasonal parasitic disease which,before the use of this vaccine, gave rise to major lossesin yearling animals. Since its introduction some 15 yearsago, the vaccine's use — many millions of doses — testi-fies to its enormous value to the livestock farmer.

Insect control

The Insect and Pest Control Section is primarilyinvolved in assisting countries to develop practical appli-cations of the sterile insect technique (SIT) as an effec-tive, inexpensive, and environmentally safe method ofinsect eradication or control. Emphasis has been placedon the Mediterranean fruit fly (medfly) and several spe-cies of the tsetse fly, which transmit the diseasetrypanosomiasis to cattle and humans. SIT requires rear-ing large numbers of insects which are then sterilizedwith gamma radiation and released in overwhelmingnumbers in the field where they mate with wild insects.These matings produce no progeny and thus lead to areduction and eventual eradication of the insect popula-tion. Thus, mass-rearing is the heart of the operation. Ithas been used successfully in eradication programmesagainst the medfly and the tsetse fly in many developingcountries.

In Mexico, mass-rearing technologies co-operativelydeveloped by the FAO and IAEA have been scaled upto rear more than 500 million medflies per week. Theyare sterilized with gamma radiation and releasedaerially. The project successfully eradicated the medflyfrom Mexico within a few years. The sterile flies arenow being used to eradicate the medfly from Guatemalaand protect Mexico from reinvasion. Savings to harvestsare estimated in hundreds of millions of dollars per year.

Rearing tsetse flies is very different from mass-rearing medflies. Tsetse flies produce one offspringevery 9 or 10 days, thus reproducing very slowly, andtheir populations in the field are very low indeed com-pared with other insects. Rearing the flies was first doneon goats, rabbits, and guinea pigs. Now artificial mem-branes using blood collected in local abbatoirs are used.This technology was used in central Nigeria and led in1987 to successful eradication of a species of tsetse flyfrom an area of 1500 square kilometres.

Environmental protection

The Agrochemicals and Residues Section directs itsefforts at increasing the safety of fertilizer and pesticideuse and reducing harmful residual effects, which may bethe result of improper as well as proper use of theseagrochemicals. As their massive inputs are a prerequi-

As part of Mexico's siT project against the medfiy, eggs wereseeded on trays of larval diet and placed in a room at constant tem-perature and humidity for 7 days so the flies fully developed.

site for high-yielding crop varieties of the green revolu-tion, effective assessment of their fate and significancein the agricultural environment is essential for properfarm land management.

By using nuclear techniques to aid studies of pesticideresidues, it has been shown that the problem withresidues in the tropics may not be as serious as previ-ously thought, provided some basic rules for applicationare followed. The high average temperatures andhumidities encountered in most developing countriesfavour much higher dissipation rates of pesticides thanare expected for temperate climates. Although someenhanced microbiological breakdown is demonstrated,much of the dissipation is due to simple volatilizationfrom plant and soil surfaces.

Currently the Section is playing a dominant role indetermining the environmental acceptability of poten-tially harmful, but highly persistent and economicallyviable, pesticides such as DDT and lindane. Co-ordinated research is being conducted mainly in tropicalregions, with a view to measuring dissipation and degra-dation rates of DDT and similar chemicals. Preliminaryresults have indicated that DDT would dissipate in majorareas of Kenya, India, and Sudan at rates which wouldpreclude local accumulation of residues in soil, plants,or wildlife.

One other activity looks to increase efficacy of arange of pesticides and thus reduce the application rateby controlled release formulations. An example is theembedding of long-lasting insecticides, such as Endosul-fan in polymers, to be used as targets for tsetse flies intropical Africa. The object is to reduce the fly populationby attracting the flies to the targets where they willreceive a lethal dose of insecticide. It is believed thatalong rivers it may be possible to drastically reduce thefly population, with very little impact to the localenvironment.

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The years ahead

Requirements for increased production of high-quality food will continue. The world's population hasjust passed the 5-billion mark and shows little signs ofslowing down. The future challenge is to sustain theworld's food production at lower cost, with reducedinputs and more concern for the environment. Furtherimprovement in crop breeding and crop animalhusbandry call for even more sophisticated technologies.

Vistas opened by new biotechnologies and geneticengineering will undoubtedly accelerate progress.

Almost every aspect of these new technologies relies onthe use of isotopic tracers or ionizing radiation. Nucleartechniques have gradually become routine tools in theagricultural laboratories of developed countries andsome advanced developing countries. Our aim is toassist the others in making routine use of these tech-niques in agricultural research. Nuclear techniques arerarely alone in research and development. They areincreasingly used as an integral and essential part in theoverall applications of modern technology in advancingfood production and sustaining the "green revolution"for years to come.

Food irradiation facilities around the world

• Irradiation facilities being used for treating food on commercial scale (28).# Irradiation facilities being built or in advanced planning stage for commercial treatment

of food or for demonstration (27).

Preserving food by radiation. Irradiation technology can reduce post-harvest food losses and increase the availability of a safe food supply.Although activities did not contribute to the green revolution, they promise to make large contributions to future food supplies. Today:• Thirty-two countries have approved altogether over 40 irradiated food items for consumption either on an unconditional or restricted basis.• Nineteen countries are using 25 irradiation facilities for processing selected food items on a commercial scale. Ten other countries are con-structing or are in an advanced stage of planning additional facilities for processing food and non-food Items. It Is anticipated that at least25 countries will use some 50 irradiation facilities for processing food items by 1990.• The International Facility for Food Irradiation Technology (IFFIT) is a joint project of FAO, IAEA, and the Ministry of Agriculture and Fisheriesof the Netherlands. To date, IFFIT has trained over 200 scientists and officials from more than 40 countries.• The International Consultative Group on Food Irradiation (ICGFI), sponsored by FAO, IAEA, and the World Health Organization (WHO),evaluates global developments and provides a focal point of advice and information In the field to Member States and the organizations. Twenty-six countries are members of ICGFI and are contributing either in cash or in kind to its programmes.

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