Food and Agriculture

Excerpt from the IAEA Annual Report for 1994

(Editor's note: The format of scientific notations in this electronic presentation is being standardized.)


Programme overview

The food and agriculture programme operated jointly with FAO is designed to assist Member States in using nuclear techniques in their agricultural research and development in order to improve the quantity and quality of food and fibre produced. This implies, among other things, optimizing the use of scarce resources for agricultural production while at the same time protecting the environment.

Progress was made in increasing the effective use of irrigation water by wheat, maize and cotton by identifying growth stages of these crops that are more resistant to drought, the amount of irrigation water required being reduced by omitting or reducing irrigation during the resistant stages. In a new CRP, the use of the 15N isotope gave rise to useful data on nitrogen dynamics under irrigated wheat. These data will be included in CERES wheat model simulations with the aim of producing recommendations to reduce pollution of groundwater by nitrogenous fertilizers. Also, genotypes of legumes with a high capability for nitrogen fixation and yield were identified. Through breeding, genotypes with the two traits were developed.

Because of a lack of staff and financial difficulties, the initiation of a CRP on the use of nuclear techniques to improve crop production in highly acid soils was postponed until further notice.

Genetic improvements in both quality and quantity of grain through induced mutations were made in sorghum and African rice in Mali. These achievements have resulted in a major programme leading to the release of promising mutants to farmers. Progress was also made in the genetic improvement of root and tuber crops by establishing procedures for combining the use of induced mutations and in vitro techniques.

Isotopes continued to play a useful role as a tool in the Agency's programme for tackling animal nutrition and health problems. A new radioimmunoassay (RIA) technique for measuring progesterone in milk was developed. This new technique requires that materials other than progesterone antibody are prepared or purchased locally in Member States, thus ensuring a greater degree of self reliance and therefore sustained use of RIA technology. From the results of field trials conducted in collaboration with the International Office of Epizootics (OIE) and WHO, the indirect enzyme linked immunosorbent assay (ELISA) technique was designated as a prescribed test for Brucella abortus in cattle by the OIE Standards Commission.

Over 2000 RIA kits for the measurement of the reproductive hormone progesterone were used in over 200 000 individual animal tests in about 50 Member States, and ELISA kits sufficient for 0.7 million individual animal tests in about 60 Member States were distributed for diagnosing diseases such as rinderpest, brucellosis, trypanosomiasis and enzootic bovine leukosis.

Major progress was made in the eradication of the Mediterranean fruit fly in the province of Mendoza in Argentina. Fruit fly populations were reduced to 99% of the original level. Commercial fruit crops are already free of the pest and in the future eradication will be carried out in urban areas. The robustness of the Vienna 42 genetic sexing strain of the Mediterranean fruit fly was widely demonstrated. Work on eradication of the tsetse fly in Zanzibar, United Republic of Tanzania, progressed well. Fly monitoring following aerial release for a period of four months indicated that over one fourth of the wild tsetse females showed signs of induced sterility.

CRPs were initiated to address the development of advanced attractant systems and mass rearing automation. Progress was made in automating the sexing of tsetse fly adults on the basis of visual imaging.

Pursuant to Agenda 21 of UNCED 1992, emphasis continued to be placed on assisting Member States to establish nuclear and related analytical techniques with which to monitor the quality of pesticide products on the market and levels of pesticide residues in food, soil, water and wildlife. Quality assurance measures were also introduced. The results of a study on the effect of methods of extraction and refining on insecticide residue levels in vegetable oils showed that different procedures do not reduce residues of all insecticides equally. It is thus possible for the farmer to select compounds which are effectively removed by the particular process used locally.

A significant milestone was the publication of English and Russian editions of Guidelines for Agricultural Countermeasures Following an Accidental Release of Radionuclides, which draws largely on information gathered following the Chernobyl accident.

Through a CRP, five methods for the detection of irradiated food were developed and tested in various countries. A feasibility study conducted in 1993 led to the decision by China and Mexico to build semi-commercial and commercial irradiation facilities, respectively. Several developing countries have introduced large quantities of irradiated food in their domestic markets.


SOIL FERTILITY, IRRIGATION AND CROP PRODUCTION

Maximizing biological nitrogen fixation and development of molecular biology techniques in microbial ecology

A regional CRP for Asia and the Pacific is using 15N isotopic techniques to measure the nitrogen fixed in different lines, cultivars and mutants of chickpea, cowpea, groundnut, mungbean and soybean. The aim is to identify superior plants and management conditions, e.g., Rhizobium inoculation that will give higher nitrogen fixation and grain yield. Plant breeding is also being used as a tool to combine the desirable genetic traits of high nitrogen fixation and high yield. Recently, attempts have been made to quantify the benefits of including high nitrogen fixing legumes into cropping systems, and the results so far have demonstrated around 20-30% cereal grain yields in legume-cereal rotations versus cereal-cereal rotations. Mixed cropping of legumes and cereals also resulted in an increased capability of grain legumes to fix N2.

Measurement of nitrogen fixation in trees and management of agroforestry systems

Through a CRP on the optimization of N2 fixation by tree crops for enhancing soil fertility and soil conservation, studies are being made of the use of the 15N methodology for investigation nitrogen fixing tress (NFTs) with a high capacity for biological nitrogen fixation (BNF), management practices that enhance BNF in NFTs and also the use of the 15N isotope dilution technique for measuring the release of N from decomposing litter of multipurpose trees. Wide differences in the BNF capacities of different NFTs and among different provenances or isolines within the same NFT have been observed; also the litter of some tree species has been found to decompose faster than others. This has important implications on differences in nutrient release for uptake be food crops grown together with these NFTs, and also, on organic matter buildup which is crucial for maintaining overall soil fertility and increasing water retention in soil.

Optimizing the use of plant nutrients for sustainable agricultural practices and environmental protection

A CRP on increasing and stabilizing plant productivity in low phosphate soils in the semi-arid and subhumid tropics and subtropics involved the search for genotypes of food crops and trees which are highly efficient in the use of limited supplies of water and phosphorus. Several genotypes of wheat tested in Morocco and Tunisia were found to be more efficient in water use than others, but only two of these, Massa and Sarif, showed the combined features of high water use efficiency and high yield. In Sierra Leone, significant genotype variation in phosphate use efficiency was discovered in the cowpea genotypes tested. Two genotypes exhibited both high phosphate use efficiency and high grain yield. In Kenya, field studies with tree species showed that from the 21 tree provenances tested, a Prosopis from Costa Rica and a Casuarina from Senegal emerged as best with respect to adaptability to phosphorous deficient soils. In the Sudan, studies with the gum arabic tree Acacia senegal revealed that three provenances were superior to the other eleven tested in their ability to survive and produce sufficient biomass in water limited environments such as those prevailing in the gum-belt region. Detailed studies with selected genotypes indicate that the root system plays a significant role in making some genotypes more efficient than others in their ability to take up and use of both water and phosphorous.

A symposium on nuclear and related techniques in soil-plant studies in sustainable agriculture and environmental preservation was held in October. The symposium assessed the progress made in the use of nuclear techniques for studying various aspects of soil fertility and plant nutrition, environmental preservation and the potential and limitations of existing methods. The proceedings contain reports of original work and comprehensive reviews of nuclear techniques for studies on fertilizer and water use by plants, biological nitrogen fixation, organic matter turnover and erosion. Highlights include the new dimensions in organic matter turnover studies through the integaration of 13C in stugies where traditionally only 15N and 14C have been used, and the recently developed marker gene technology which has greatly facilitated studies on the ecology of soil microorganisms such as rhizobia.

Increasing the effective use of scarce water resources to maximize plant productivity

A CRP on the assessment of irrigation schedules of field crops to increase the effective use of water in irrigation projects has identified growth stages of maize, wheat and cotton that are most resistant to drought. These stages were: the vegetative stage in maize (in contrast to the flowering stage), the tillering and ripening stages in wheat (as against the stem extension and heading growth stages), and the ball formation stage of cotton (in contrast to the vegetative stage). Thus by reserving the water, which otherwise would have been applied unnecessarily during the more drought resistant stages, optimum crop growth and yield can still be obtained with minimum irrigation water requirements.

Increasing plant productivity in deleterious soils with emphasis on saline and highly acid soils

A CRP on the use of nuclear techniques to improve crop production on salt-affected soils was completed and an IAEA-TECDOC will be published in 1995. The results showed that a wide genetic variability exists for salt tolerance in all crop and tree species. Millet and sorghum grown in salt affected soils showed a significant decrease in both salinity and sodicity, while the growth of barley, rice (variety Bastani 370) and Sesbania aculeata and Kallar grass ameliorated salt affected soils.

Laboratory activities

Isotopic studies at the Agency's Laboratory of Seibersdorf contributed to the development and transfer of nuclear technology in soil science and plant productivity in support of the various CRPs. These techniques were used in various ways to optimize the use of soil resources (nutrient and water) for increasing crop productivity and minimizing the impact of the excess use of fertilizer on the environment.

The primary role of the Laboratory is to provide support in terms of R&D, training, analytical and other services. Approximately thirty field, greenhouse and laboratory experiments were conducted in 1994.

The Laboratory provided 47 person-months of training to 19 fellows on the use of isotope and related nuclear techniques in soil/plant studies and isotope analysis. Analytical services, mainly nitrogen isotopic ratio determinations of approximately 12 500 plant and soil samples, were provided for the implementation of CRPs and technical co-operation projects.


PLANT BREEDING AND GENETICS

Crop improvement in Latin America

The first Research Co-ordination meeting on induced mutations in connection with biotechnology for crop improvement in Latin America was held in October in Guatemala. This recently started programme will build on results and experience from the regional technical assistance given to most of the participants. Areas of research and strategies were discussed for crops such as rice, wheat, barley, quinoa, banana, sugarcane, chrysanthemum, citrus and grape. Advanced plant material and putative mutants will be further evaluated. Applications of in vitro techniques will be developed with the focus on doubled haploid techniques, somatic and micropropagation as well as the use of molecular genetics.

Genetic improvement of basic food crops in Africa

Promising results were achieved in technical co-operation projects and the CRP on the genetic improvement of basic food crops in Africa through plant breeding, including the use of induced mutations. In Mali, several improved mutants of the local varieties of sorghum and African rice (Oryza glaberrima) were obtained by gamma irradiation. The mutants of sorghum have short height, improved grain quality and increased drought tolerance. Two mutants have light orange coloured, vitreous grain, which is preferred by the local people for cooking. Seeds were made available to local farmers, but without any official performance tests and there is insufficient certified seed for carrying out subsequent multilocation field trials. It is now proposed to test the selected mutants in multiplication trials, officially release them as variety(ies) and subsequently multiply seed for distribution to the growers. The mutants of African rice have white grains instead of the red kernel of the parental variety and one of them is much earlier in maturity. The white grain rice sells at a premium price over the red grain types. Overall performance and consumer acceptance will have to be tested further before they can be considered for official release as varieties.

Genetic improvement of oil seed and industrial crops

The first Research Co-ordination meeting for the programme on mutation induction for sesame improvement was held. Recommendations were made on methods for mutagen treatment, management of M1 and subsequent generations, general selection procedures with emphasis on selection for disease resistance and the specific breeding objectives for the future.

Biotechnology for the improvement of vegetatively propagated crops

A CRP on in vitro mutation breeding of bananas and plantains was completed and reports summarizing five years of research were published in an IAEA-TECDOC. Biotechnological developments have provided new tools for the improvement of Musa through mutation breeding. However, some obstacles still remain in the protocols for mutation induction and screening, and problems related to chimerisms and ploidy level of variants must be overcome. Furthermore, it was recognized that more effort is required for research in the use of cell and protoplast cultures for mutation induction.

In vitro technology for mutant selection

The first Research Co-ordination meeting on in vitro techniques for selection of radiation induced mutants adapted to adverse environmental conditions was held in April. The main objective of this CRP is develop in vitro procedures for irradiation of plant tissues and cells and rapid isolation and multiplication of mutants suitable for adverse environmental conditions such as salinity, drought, high temperature, cold, flooding and aluminium toxicity. The interest of the participants covers topics such as tolerance to water-logging in sugarcane (Bangladesh), tolerance to frost (Colombia) and salinity (Egypt and Pakistan), high temperature and late blight (India) in potato, drought tolerance and resistance to African Cassava Mosaic Virus in cassava (Kenya), tolerance to acid soils and fusarium wilt in banana (Malaysia), and drought tolerance and Moko disease resistance in plantain (Guyana). The development of in vitro selection for salinity and characterization of the cloned gene functions in alfalfa (USA) was presented.

Laboratory activities

The R&D activities of the Agencys Laboratory at Seibersdorf focused on mutation induction to create genetic variation with minimal plant injury and to increase the overall efficiency of this system in plant breeding with special emphasis on crops such as banana, plantains, cassava and rice, which are of importance to developing countries. In vitro micropropagation is routinely applied to build up appropriate plant populations for mutation induction. However, mutagenic treatment of complex multicellular systems will always give rise to the problem of causing chimeras. Somatic embryogenesis and other tissue culture techniques are under investigation to prevent this problem from occurring. Genetic markers, i.e. rapid amplified polymorphic ONA and DNA fingerprinting, are used to detect genetic diversity in putative mutants. Molecular biology techniques are explored and evaluated for their usefulness in mutation breeding for developing early screening techniques for the determination of mutant genotypes with more resistance to pathogens and environmental stress.

In rice breeding, studies focused on three approaches for in vivo and in vitro mutation breeding, i.e. irradiated anther culture, somatic embryo culture from irradiated roots and induction of multiple shoots from irradiated seeds. The work resulted in an increased efficiency in haploid plant regeneration from anther culture after cold pre-treatment and anther incubation, as well as in the development of an improved technology to re-establish the original diploid level. A high number of mutants was observed and selected for traits such as stem height, maturity period, plant shape, panicle size and grain size. Progenies of these materials are currently under field evaluation for genetic confirmation. Somatic embryos were obtained from root culture segments and plants derived from somatic embryos were transplanted in pots and the seed collected for evaluation of genetic variation in the M2 generation.

Somatic embryogenesis was induced in recalcitrant African cassava clones. The clone with the highest regeneration capability was chosen for radiosensitivity tests. Somatic embryos were irradiated at doses between 2 and 60 Gy. Doses lower than 15 Gy had no significant influence over cassava regeneration. Mixoploidy was induced to study chimera behaviour and the number of in vitro subcultures needed for establishment of solid mutants.

The Laboratory continued to provide training on appropriate technologies to solve specific problems in the field of plant mutation breeding. Local cultivars of different species were brought by scientists from developing countries to the Seibersdorf Laboratories and used for experimental work. Protocols and techniques arising from this collaboration were directly applied in national breeding programmes.

The Laboratory also continued to provide services in the mutagen treatment of seeds, organs and tissue culture in support of mutation breeding activities in Member States. The services included the establishment of optimal doses and bulk irradiation of plant material for both practical breeding and basic research in plant genetics.


ANIMAL PRODUCTION AND HEALTH

Development of feeding and breeding strategies for improving the productivity of ruminant livestock in developing countries

Under an interregional CRP involving animal production research institutes in Asia and Latin America, measurements of progesterone by RIA and of nutritional metabolites by colorimetric methods are being used to assess the reproductive and nutritional status of dairy cattle kept by smallholder farmers. At present, these measurements are being used along with basic productivity parameters to identify management and nutritional constraints to milk production. Later, participants will investigate simple, low-cost interventions based on locally available feed resources for improving milk production as well as monitor the sustainability of these interventions.

Over the past ten years, counterpart laboratories have been provided with a standardized RIA kit for measuring progesterone, based on a coated tube, non-extraction method. In order to ensure the sustained use of RIA technology, a greater degree of self-reliance in the preparation of RIA components by counterparts is important. Thus, a so called self-coating RIA method for progesterone determination in milk has been developed at the Agency's Laboratories and in future bulk quantities of progesterone antibody will be supplied by the Agency and the remaining materials (125I labelled progesterone, tubes, buffers and standards) will be either purchased directly or prepared locally by the end user.This approach has been field tested in several counterpart laboratories and technology transfer will be carried out in a controlled manner to selected laboratories during the forthcoming year.

Validation and use of immunoassay tests for the diagnosis of trypanosomiasis in African livestock

A CRP was initiated to use immunoassays developed jointly by ILRAD in Kenya and the Agency's laboratory at Seibersdorf to monitor tsetse and trypanosomiasis control programmes in 14 African countries. These tests are much more sensitive and specific than conventional parasitological methods to detect trypanosomiasis in cattle blood and can therefore provide a more accurate indication of the progress of control programmes based on drugs or insecticides. These tests are also being used to monitor the effectiveness of the SIT project being conducted on Zanzibar.

Validation and international standardization of immunoassay test kits for the diagnosis and surveillance of selected bacterial and parasitic diseases of livestock in developing countries

The FAO/IAEA Central Laboratory continued to develop standardized ELISA based approaches for the diagnosis of animal diseases. Of particular importance was a field trial conducted in collaboration with OIE and WHO to evaluate an indirect ELISA for the detection of antibodies to Brucella abortus in cattle. As a result of the trial, the OIE Standards Commission agreed that this test was now sufficiently validated to be designated as a prescribed test for B. abortus in cattle. This means that the test can be used for the diagnosis of bovine brucellosis for the purposes of international trade.

An external quality assurance system was developed for recognizing the diagnostic competence of national testing laboratories for particular diseases. Laboratories using FAO/IAEA immunoassay kits will henceforth be required to test a number of blind samples twice a year. This approach should assist developing countries in overcoming livestock trade restrictions arising from the suspected presence of diseases in the exporting country.

Laboratory activities

In 1994, the Central Laboratory provided over 2000 RIA kits for the measurement of the reproductive hormone progesterone to counterpart laboratories in approximately 50 Member States, representing over 200 000 individual animal tests.

In addition, the Laboratory provided clinical chemistry kits for the measurement of nutritional metabolites and trace minerals to 16 countries in support of a CRP on feeding strategies for milk producing livestock. Approximately 80 kits for the measurement of total serum protein, serum albumin, blood urea/nitrogen, -hydroxy butyrate and inorganic phosphorus were shipped from Seibersdorf, together with detailed manuals and controls and standards.

The Laboratory continued its support of animal health programmes through the provision of FAO/IAEA enzyme immunoassay (ELISA) kits to counterpart laboratories in about 60 Member States. These kits and their reagents and protocols have been standardized in collaboration with major veterinary research centres throughout the world. In 1994, kits sufficient for 0.7 million individual animal tests for diagnosing diseases such as rinderpest, brucellosis, trypanosomiasis and enzootic bovine leukosis were distributed.


INSECT AND PEST CONTROL

Improved economy and reliability of the sterile insect technique for use against fruit flies

Major progress was made in the eradication of the Mediterranean fruit fly in the Province of Mendoza in Argentina. In collaboration with the provincial and federal governments, all activities of the sterile insect technique (SIT) programme were scaled up and 200 million sterile flies are now being released weekly covering the 500 hectares of orchards and urban areas of the province. Commercial fruit crops are already free of the pest and eradication in urban areas will be attempted in the season 1995-1996. A quarantine barrier with ten inspection stations along all passes over the Rio Colorado has been established, so that preparatory activities for a similar SIT eradication programme in the Patagonia provinces can be initiated.

The Mediterranean fruit fly mass rearing facility in Arica, Chile, also started operation in 1994. At present, preventive sterile fly releases are being made along the northern border, to intercept wild flies moving in from southern Peru. Another programme was initiated in Madeira, Portugal, with the objective of using the SIT against the Mediterranean fruit fly, the only fruit fly on the island. The sterile fly mass rearing facility has been designed and construction will be initiated in early 1995.

Improved economy and reliability of the sterile insect technique for use against tsetse fly vectors of animal trypanosomiasis

The tsetse fly SIT eradication programme on Zanzibar, Tanzania, made rapid progress. For the first time, sterile tsetse flies were released by air. According to schedule, the entire southern part of the island, including the Jozani and Muyuni forests where the highest tsetse populations are located, is now under aerial sterile fly releases. Sterile flies are being reared at the facility in Tanga, United Republic of Tanzania, in addition to those produced at the Seibersdorf Laboratories. The first phase of the refurbishment of the Tanga facility is completed, thereby increasing significantly the sterile fly production capacity. Fly monitoring indicates that already one fourth to one third of all wild tsetse females captured in the entire southern part of the island show signs of induced sterility. With increasing fly production, the aerial release of sterile flies will be extended progressively to the northern half of the island.

Laboratory activities

Under a recently completed CRP, progress was made in the development of genetic sexing strains for field application in SIT programmes. A critical aspect in this relates to the mass rearing characteristics of the temperature sensitive strain, Vienna-42. In support of a technical co-operation project in Tunisia, approximately one million sterile male medflies from the above strain were supplied weekly for field release. During this large scale rearing and shipping exercise many quality parameters of the strain were checked. These included strain stability, male production, shipping effects and field performance; in no case was the Vienna-42 strain inferior to a pupal colour sexing strain that was also produced and shipped under the same conditions. On the basis of these results and previous field tests with the strain, there is now confidence that Vienna-42 demonstrates the necessary robustness to play an important role in large scale SIT programmes for the eradication of the medfly. The strain was recently supplied, upon request, to the fruit fly mass rearing factories in Hawaii and Guatemala.

Further advances in genetic sexing technology will arise from research being conducted at the Agencys Laboratories Seibersdorf and through a CRP in the area of molecular biology, specifically in the analysis of male determining genetic elements. It has now been clearly demonstrated in the medfly that the element responsible for maleness can be localized to a very small part of the Y chromosome. This provides the basis for attempts to clone the gene, which are at present under way.

The Laboratory has also initiated research into a fine grained analysis of medfly mating behaviour using video analysis. Although mating is the critical behavioural component required for the SIT, very little is known about it in the medfly and, more importantly, no information is available on strain and geographic variation. This research aims at improving quality control procedures for mass reared medflies.

The use of radiation as a quarantine methodology for fruit flies is gaining greater acceptance; its major drawback is that it does not always kill the insect immediately and quarantine inspectors cannot identify if an insect has been irradiated or not. A simple colorimetric test has now been developed in the Entomology Unit on the basis of the enzyme phenoloxidase. The test is simple and cheap and is now suitable for larger scale testing.

Work in the tsetse group has been dominated by support to the project for the eradication of Glossina austeni from Zanzibar using the SIT. This has resulted in a continued expansion of the G. austeni colony at Seibersdorf in order to supply the project with sufficient flies both for field release and to build up the breeding colony at the Tanga insectary in the United Republic of Tanzania. In the first months of the year, almost 200 000 breeding females were being maintained in Seibersdorf and approximately 150 000 pupae were being shipped every month to Tanga.

A critical factor to enable any laboratory to produce good quality tsetse flies is a guaranteed supply of high quality blood. In-house technology and expertise was utilized to supply 1000 litres of irradiated frozen bovine blood to the laboratory in Tanga in 1994. Progress has been made, in collaboration with the Technical University of Vienna, in automating the sexing of tsetse adults on the basis of visual imaging.


AGROCHEMICALS AND RESIDUES

Monitoring pesticide residues in food and the environment

A CRP completed in 1994 evaluated a variety of methods for extracting and refining vegetable oils with regard to their effectiveness in removing pesticide residues. Over 20 methods from 12 countries were examined, involving soybean, cottonseed, rapeseed, sunflower, palm, olive and coconut. In general, steam deodorization was effective for removing organochlorine residues while alkali treatment was effective for organophosphorus compounds but other processes also removed particular compounds.

Work on the effects of organochlorine insecticides on flora and fauna in Africa, which uses lindane as the model compound, confirmed the 1993 observations that the numbers of soil living insects are usually reduced for about two months following application. An improved methodology allowed the numbers of aerial insects to be recorded and these showed no effects from the insecticide. Organic matter breakdown in the soil was reduced at some but not all sites. Lindane reduced damage by maize stem borers in almost all cases but this was not well correlated with crop yield. An important element of this programme is to adapt methods usually developed in temperate countries for use under African conditions.

A companion programme for Central America (where climate, crops and pesticide use are very different from those in Africa) was started; this will be closely integrated with the Programme on Environment and Health in the Central American Isthmus (MASICA). Considerable attention will be paid to pesticides in water resources.

The first results from a CRP comparing immunochemical with conventional methods for pesticide residue analysis were produced. Despite considerable interlaboratory variation, there was an encouraging similarity in values obtained for the insecticide dieldrin in soil samples. There were, however, indications that some soil and water samples contained components that interfere with the immunochemical response.

Development of controlled release and other formulations of pesticides using nuclear techniques

Results for both wet and dry seasons were reported for studies of the effects of additives on the uptake and activity of herbicide glyphosate in the commercial formulation using 14C labelled material as a tracer. Additional surfactants generally improved glyphosate performance on the sedge Cyperus rotundus (purple nutsedge), which is generally acknowledged to be the world's worst weed. However, the most effective treatment varied from country to country and results for the wet season were different from those in the dry season. Once the reasons for the variability are understood the prospects for a substantial improvement in the control of this weed are good.

Laboratory activities

The Agencys Laboratory Seibersdorf was heavily involved with a number of CRPs, particularly those concerned with the ecological effects of insecticides in Africa and Central America and the use of nuclear and immunochemical methods of analysis. Analytical quality assurance services were provided for several CRPs and some technical co-operation projects.

Field and laboratory tests of insecticides applied to tsetse fly targets as aqueous formulations have indicated that the use of high concentrations does not significantly improve the efficacy of the targets, indicating that the insecticide degrades quickly regardless of the concentration. However, the use of oil formulations of the insecticides with an added ultraviolet absorber compound enhances the environmental stability and toxicity to the flies. This technique was found to work with the organopyrethroid insecticides including permethrin, a relatively inexpensive, but also environmentally less stable, insecticide.


FOOD PRESERVATION

Acceptance of irradiated food in international trade

The mandate of the International Consultative Group on Food Irradiation (ICGFI) was extended for another five years, i.e. until May 1999. China, Croatia, and the Republic of Korea became members of ICGFI, bringing the total membership to 42. The principles and guidelines developed by ICGFI, especially in the area of irradiation as a quarantine treatment of fresh fruits and vegetables, received increasing recognition by governments and regional and international organizations.

Control of the food irradiation process

The CRP on analytical detection methods for irradiation treatment of food was completed. Five detection methods (electron spin resonance, thermoluminescence, lipid hydrocarbons, ortho-tyrosine and microbiological analysis) have been developed to detect a large variety of irradiated food and their reliability has been confirmed through a series of collaborative trials.

Demonstration of technoeconomic feasibility of food irradiation in developing countries

As a result of a feasibility study conducted in 1993, three companies in Mexico have decided to build commercial food irradiation facilities to process food items for both domestic and export markets. China is building a semi-commercial irradiator in Beijing to process rice, garlic, spices and other food items with some input from the Agency. Feasibility studies conducted in Brazil and the Islamic Republic of Iran during 1994 showed positive results. Several developing countries, including Bangladesh, Chile, China, Indonesia, the Republic of Korea, Mexico and Thailand, have introduced larger quantities of irradiated food into their domestic market.

Use of irradiation in combination with other food processes

With the global phasing out of methyl bromide, the most widely used fumigant for food and agricultural products, by the year 2000, much larger quantities of irradiated food in both advanced and developing countries are expected to be processed by irradiation in the near future. Through consultants services, data have been compiled on the wholesomeness of food treated by irradiation in combination with other food processes (at doses above 10 kGy). The data will be made available for evaluation by the Joint FAO/IAEA/WHO Expert Committee on the Wholesomeness of Irradiated Food following a recommendation of the ICGFI in 1995.

General activities

The Action Plan for Food Irradiation Activities with Technical Co-operation Assistance during the period 1995-1996 was endorsed by the Board of Governors. This Action Plan will be implemented in addition to on-going technical co-operation projects and will include pre-project missions, economic feasibility studies and resource requirements. A four-year project on improving safety and quality of food and food ingredients in trade by irradiation has been agreed by FAO, IAEA, WHO and the International Trade Centre for joint implementation in 1995. The first phase of the project will deal exclusively with promoting international trade in irradiated spices and dried vegetable seasonings and will address problems related to: quality maintenance and safety in spice producing/exporting countries; a marketing/information campaign in spice importing/consuming countries; and feasibility studies on irradiation as a means of decontaminating spices.