Robin D. Graham

A new paradigm for world agriculture: meeting human needs: Productive, sustainable, nutritious

Micronutrient malnutrition (‘Hidden Hunger’) now afflicts over two billion people worldwide, resulting in poor health, low worker productivity, high rates of mortality and morbidity, increased rates of chronic diseases (coronary heart disease, cancer, stroke, and diabetes), and permanent impairment of cognitive abilities of infants born to micronutrient-deficient mothers. The consequences of food system failures include lethargic national development efforts, continued high population growth rates, and a vicious cycle of poverty for massive numbers of underprivileged people in all nations. Our food systems are failing us globally by not providing enough balanced nutrient output to meet all the nutritional needs of every person, especially resource-poor women, infants and children in developing countries. Agriculture is partly responsible because it has never held nutrient output as an explicit goal of its production systems. Indeed, many agricultural policies have fostered a decline in nutrition and diet diversity for the poor in many countries. Nutrition and health communities are also partly responsible because they have never considered using agriculture as a primary tool in their programs directed at alleviating poor nutrition and ill health globally. Now is the time for a new paradigm for agriculture and nutrition. We must consider ways in which agriculture can contribute to finding sustainable solutions to food system failures through holistic food-based system approaches, thereby closely linking agricultural production to improving human health, livelihood and well being. Such action will stimulate support for agricultural research in many developed countries because it addresses consumer issues as well as agricultural production issues and is, therefore, politically supportable. # 1999 Elsevier Science B.V. All rights reserved.

Breeding for micronutrient density in edible portions of staple food crops: conventional approaches

Abstract Current and past efforts in breeding for industrial quality (processing, malting, baking, extruding, etc.), as opposed to yield, are reviewed as a prelude to discussion of the criteria that need to be met in breeding programs to improve the nutritional quality of crops for human consumption. In field crops, almost no attempts to improve nutritional value have been made. Recent studies in fact indicate that most criteria can be easily satisfied: existence of sufficient genetic variation, suitable selection methods and markers, workable heritabilities, and compelling reasons for doing so. However, establishing the efficacy in deficient human populations of elite material chosen by simple selection criteria is a major challenge that requires collaboration with human nutritionists. In some cases, developing marketing strategies for nutritionally superior types that may not – by color or other characteristics – appeal to target communities is also an issue breeders must bear in mind. Nevertheless, the fact recently established that desirable traits can be combined with high yield overcomes many obstacles. The widely demonstrated acceptance of new cultivars by farmers, in developing as well as industrialized countries, will ensure high impact of worthwhile improvements in nutritional value. To combine these new traits with high yield will increase the cost of breeding programs considerably, but the benefit–cost ratio is likely to be larger also.

Addressing micronutrient malnutrition through enhancing the nutritional quality of staple foods: Principles, perspectives and knowledge gaps

Abstract Five years ago, with international funding, several international agricultural research centers set out to explore the potential to improve the micronutrient quality of some staple food crops. Five objectives were identified, and all needed a favorable result if breeding for higher micronutrient density in the staples were to be deemed feasible. Useful genetic variation to exploit was needed. The traits needed to be manageable in a breeding program (simple screening and high heritability), and stable across a wide range of environments if impact was to be large. Above all, the traits needed to be combinable with traits for high yield to ensure that farmers chose the improved lines. Finally, it was necessary to show that the new types actually improved the health of humans of low nutrient status representing the target populations. The extra nutrients needed to be bioavailable to the gut. Today, only this last essential criterion remains to be fully satisfied. All other criteria are met to levels that lead us to claim that breeding for nutritional quality is a viable, practicable, and cost-effective strategy to complement existing interventionist strategies. Subject to satisfying the last criterion, and results are encouraging, we call for a major funding initiative, and the installation of a new paradigm for 21st century agriculture: one espousing food systems that are highly productive, sustainable, and nutritious. This paper reviews the case for and the rationale behind the project that is underway, gives an overview of the results to date and looks at the critical issues that still remain to be confronted.

Selecting zinc-efficient cereal genotypes for soils of low zinc status

Deficiencies of zinc are well known in all cereals and cereal-growing countries. From physiological evidence reported elsewhere, it would appear that a critical level for zinc is required in the soil before roots will either grow into it or function effectively; it is likely the requirement is frequently not met in deep sandy, infertile profiles widespread in southern Australia. Because fertilizing subsoils is impractical, this paper presents arguments for breeding cereal varieties with root systems better able to mobilise zinc from soil sources of low availability. Other agronomic arguments are presented in support of breeding for zinc efficiency.

Nutritious subsistence food systems

The major subsistence food systems of the world that feed resource‐poor populations are identified and their capacity to supply essential nutrients in reasonable balance to the people dependent on them has been considered for some of these with a view to overcoming their nutrient limitations in sound agronomic and sustainable ways. The approach discusses possible cropping system improvements and alternatives in terms of crop combinations, external mineral supply, additional crops, and the potential for breeding staples in order to enhance their nutritional balance while maintaining or improving the sustainability and dietary, agronomic, and societal acceptability of the system. The conceptual framework calls for attention first to balancing crop nutrition that in nearly every case will also increase crop productivity, allowing sufficient staple to be produced on less land so that the remaining land can be devoted to more nutrient‐dense and nutrient‐balancing crops. Once this is achieved, the additional requirements of humans and animals (vitamins, selenium, and iodine) can be addressed. Case studies illustrate principles and strategies. This chapter is a proposal to widen the range of tools and strategies that could be adopted in the HarvestPlus Challenge Program to achieve its goals of eliminating micronutrient deficiencies in the food systems of resource‐poor countries.

Breeding crops for enhanced micronutrient content

Micronutrient malnutrition (e.g. Fe, Zn and vitamin A deficiencies) now afflicts over 40% of the worlds population and is increasing especially in many developing nations. Green revolution cropping systems may have inadvertently contributed to the growth in micronutrient deficiencies in resource-poor populations. Current interventions to eliminate these deficiencies that rely on supplementation and food fortification programs do not reach all those affected and have not proven to be sustainable. Sustainable solutions can only be developed through agricultural system approaches. One agricultural approach is to enrich major staple food crops (e.g. rice, wheat, maize, beans and cassava) in micronutrients through plant breeding strategies. Available research has demonstrated that micronutrient enrichment traits are available within the genomes of these major staple crops that could allow for substantial increases in Fe, Zn and provitamin A carotenoids without negatively impacting yield. Furthermore, micronutrient-dense seeds can increase crop yields when sowed to micronutrient-poor soils. The enrichment traits appear to be stable across various soil types and climatic environments. Further research is required to determine if increasing levels of micronutrients in staple foods can significantly improve the nutritional status of people suffering from micronutrient deficiencies.

Breeding for Trace Mineral Density in Rice

In 1992 the International Rice Research Institute (IRRI) began to examine the effect of certain soil characteristics on the iron content of rice grains. As part of the Consultative Group for International Agricultural Research (CGIAR) Micronutrients Project, this effort was expanded in 1995 to include analysis of both iron and zinc, in collaboration with the University of Adelaide in Australia. Since then, germplasm screening has shown large genetic variation for iron and zinc concentrations in brown rice. Common cultivars contain about 12 mg of iron and 25 mg of zinc per kilogram. Some traditional varieties have double these amounts. Genetic-by-environmental interactions are sufficiently moderate that breeding for higher iron and zinc content is considered worthwhile. The next major research step will be to further study the genetics of trace mineral accumulation in the grain to determine the best selection techniques for use in breeding. High iron and zinc traits can be combined with improved agronomic traits. This has already been demonstrated in the serendipitous discovery in the IRRI testing programme of an aromatic variety (IR68144-3B-2-2-3) that has a high concentration of grain iron, about 21 mg/kg in brown rice. This elite line has good tolerance to rice tungro virus and to mineral-deficient soils and has excellent grain qualities. The yields are about 10% below those of IR72, but in partial compensation, maturity is earlier. After 15 minutes of polishing, IR68144-4B-2-2-3 had about 80% more iron than IR64, a widely grown commercial variety. It remains to be shown that this extra iron can improve the iron status of iron-deficient human subjects. A human feeding trial is being planned.

Breeding for Trace Minerals in Wheat

In the search for genetic material with high iron and zinc concentration in wheat grain, a significant positive correlation has been found between iron and zinc concentrations, suggesting that these two traits may be combined relatively easily during breeding. In future research, the very high values of iron and zinc in the grain seen in wild types and landraces need to be confirmed in trials in which all the best material is planted in the same location and year. In addition, it is important to determine if these high levels of iron and zinc in the grain can be maintained in high-yielding material. The production of semi-dwarf wheat through the introduction of the rht genes has resulted in substantial yield increases. However, this is associated with a reduction in iron and zinc concentrations in some bread wheat genotypes, but not in durum wheat. The presence of the 1B/1R translocation in the wheat germplasm of the Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) to increase leaf rust resistance may have had a positive effect on the concentration of iron and zinc, but a negative effect was ruled out. There is a strong positive correlation between grain yield and year of release in the CIMMYT wheat varieties. There is a small negative but statistically significant relationship between the time of release and the concentrations of iron, zinc, total phosphorus, and phytate. The positive effect of nitrogen applications on iron and zinc concentrations is more important than declines in these concentrations due to breeding during the last 42 years

Effects of Nutrient Stress on Susceptibility of Plants to Disease with Particular Reference to the Trace Elements

Publisher Summary This chapter considers the biochemistry, physiology, and agronomy of trace elements in plants in so far as they may influence host–pathogen relationships. Each of the micronutrients can be identified with specific biochemical pathways, so their effects on disease offer avenues for elucidating mechanisms of resistance in higher plants. Certain general principles may be demonstrated, but the complex nature of many interacting factors influencing plant health limits the extent to which simple patterns emerge. The quest for general principles is stimulated by the increasing prevalence of micronutrient deficiencies in modern agricultural systems, in which the use of the appropriate micronutrients may be seen as a form of biological control. In contrast to the largely structural, conformational, and osmotic roles of the macronutrients, the micronutrients act as catalysts, cofactors, and inhibitors. In these roles, supraoptimal concentrations are physiologically important. A number of trace elements, which are not recognized as essential to plants, strongly influence the host–pathogen balance. Criteria of essentiality are usually established in artificial conditions of laboratory and glasshouse. The chapter summarizes the principles which emerge from a study of macronutrient effects on incidence of disease in higher plants and the principles that seem to emerge from a study of the micronutrient effects on susceptibility to disease.

Efect of zinc and iron deficiency on phytos1derophore release in wheat genotypes differing in zinc efficiency

Abstract The effect of varied zinc (Zn) and iron (Fe) supply on the release of Zn and Fe mobilizing phytosiderophores from roots was studied in Zn‐efficient Aroona and Zn‐inefficient Durati wheat genotypes (Triticum aestivum cv. Aroona; T. durum cv. Durati) grown under controlled environmental conditions in nutrient solution for 25 days. Phytosiderophore release was determined by the measurement of Zn and Fe mobilizing capacity of root exudates from a Zn‐loaded resin and from freshly precipitated FeIII hydroxide as well as identification by HPLC analysis. Visual Zn‐deficiency symptoms, such as necrotic patches on leaves and reduction in shoot length, appeared first and more severely in Zn‐inefficient Durati, although the concentrations of total Zn in shoot and root tissues were the same in both genotypes. Zinc‐efficient Aroona responded to Zn deficiency by increasing phytosiderophore release usually after 10 days growth in nutrient solution, whereas the phytosiderophore release in Durati remained at a ver...