Advances in Agronomy

1. Auflage 2014
ISBN: 978-0-12-800359-6
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 125, 324 Seiten

Reihe: Advances in Agronomy

Advances in Agronomy continues to be recognized as a leading reference and a first-rate source for the latest research in agronomy. As always, the subjects covered are varied and exemplary of the myriad of subject matter dealt with by this long-running serial. - Maintains the highest impact factor among serial publications in agriculture - Presents timely reviews on important agronomy issues - Enjoys a long-standing reputation for excellence in the field

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Chapter Two Agronomic Biofortification of Cereal Grains with Iron and Zinc
Rajendra Prasad*,†,1; Yashbir S. Shivay†; Dinesh Kumar†    * Indian National Science Academy, New Delhi, India
† Division of Agronomy, Indian Agricultural Research Institute, Pusa, New Delhi, India
1 Corresponding author: email address: [e-mail] Abstract
Iron and zinc deficiencies in human nutrition are widespread in developing Asian and African countries where cereal grains are the staple food. Effects are therefore underway to develop cereal genotypes with grains denser in Fe and Zn by traditional plant breeding or using genetic engineering techniques. This approach requires a long period and adequate funds. However, the products of genetic engineering are not well accepted in many countries. Also, there is a trade-off between yield and grain biofortification. Agronomic biofortification offers to achieve this without sacrificing on yield and with no problem of product acceptance. From the viewpoint of biofortification, foliar application has been reported to be better than the soil application of Fe and Zn, and for this purpose, chelated Fe and Zn fertilizers are better. When soil applied, water soluble sources of Zn are better. Soil application of Fe is not recommended. Agronomic biofortification depends upon management practices (tillage, water management, nutrient interactions), soil factors (amounts present, pH, mechanisms of Zn fixation other than pH), and plant factors (root characteristics, excretion of phytosiderophores and organic acids by roots, Zn utilization at the cellular level, translocation within plant and mechanisms of Zn accumulation in grain). Genetic and agronomic biofortification are complementary to each other. Once the genotypes having denser grains are developed, they will have to be adequately fertilized with Fe and Zn. However, much more research in agronomy, soil science, and plant physiology is needed to understand the complex soil–plant–management interaction under different agroecological conditions under which cereals are grown. The situation is more complex for rice, which is grown under flooded, upland, and intermediate water conditions. Keywords Biofortification Micronutrients Anemia Diarrhea Dwarfism Disability-adjusted life years Zn prosthetic groups Phytosiderophores Cereals 1 Introduction
Cereals are staple food in most developing low-income countries of Asia and Africa, where they may contribute as much as 55% of the dietary energy (Fig. 2.1). Rice feeds more than half the world population and meets 21% of energy and protein needs of human population globally (McLean et al., 2002). About 90% of rice is grown and consumed in South, South-east, and East Asia, where about 62.5% of the world's total 925 million hungry people reside; about 25.8% of world's hungry people reside in sub-Saharan Africa (FAO, 2010). Apart from hunger and malnutrition per se, Fe deficiency anemia affects 88% of the pregnant women in South Asia, contributing to maternal mortality and impaired mental development in vast number of children (IRRI, 2006); in 2009, about 60% of the under-5-year children were underweight in the 20% poorest group in this region (UN, 2011). About 2 billion people suffer globally due to Fe deficiency anemia, mostly in developing countries (Stolzfus and Dallman, 1998). As many as 79.1% of India's children between the ages of 3 and 6 years, and 56.2% of married women (15–49 years) are anemic (Krishnaswamy, 2009). Vitamin A deficiency affects 169 million preschool children in South and Southeast Asia (33% of all preschool children) and 104 million (32% of all preschool children) in sub-Saharan Africa (IRRI, 2006). It is estimated that 60–70% of population in Asia and sub-Saharan Africa could be at risk of low Zn deficiency intake (Gibson, 2006); in absolute numbers, this translates to 2 billion people in Asia and 400 million people in sub-Saharan Africa (IRRI, 2006). More than one-third of the world's population suffers from Zn deficiency (Hotz and Brown, 2004; Stein, 2010), and Zn deficiency has been estimated to be responsible for approximately 4% of the worldwide burden of morbidity and mortality in under-5-year children and a loss of nearly 16 million global disability-adjusted life years (Black et al., 2008; Walker et al., 2009). Pirzadeh et al. (2010) reported that in Iran, rice provided 96% and 42% of the dietary Fe needs for male and female adults, respectively; the values for Zn were only 30% and 22% for male and female adults, respectively. Cereal grains are inherently low in concentration as well as bioavailability of Zn, particularly when grown on Zn-deficient soils (Cakmak et al., 2010a; Welch and Graham, 2004). Figure 2.1 Contribution of cereals to the dietary energy in high-income and low-income countries. From FAO (2008). Wheat is the second staple cereal after rice in South Asia (India, Pakistan, Nepal, and Bangladesh) (Prasad, 2005), China, and Turkey (Chatrath et al., 2007) and is responsible up to 70% of the daily calorie intake of population living in rural areas in some of these countries (Cakmak, 2008; Zhang et al., 2010a). In Asia, China is the major corn-producing country, while in Africa it is a major cereal in Egypt, South Africa, Zimbabwe, Malawi, and several other countries. In 2010, the United States produced 37.8% of the total corn produced in the world, while China produced 20%. Of course in most corn-producing countries, human nutrition is better, due to use of more meat, poultry, fish, etc. 2 Biofortification of Cereal Grains
In view of globally widespread deficiencies of vitamin A, Fe, I, and Zn in humans, the problem was first attended to by physicians and nutritionists. A number of Vitamin A and Fe containing nutrition supplements are available off-the-shelf throughout the world; Zn has been recently added to vitamin and mineral supplements (Haider and Bhutta, 2009; Hess and King, 2009). National Institute of Nutrition, Hyderabad, India, has developed common salt fortified with both Fe and I (Sesikaran and Ranganathan, 2009). The other approach adopted by nutritionists is an enrichment of cereal-based traditional foods with vitamins and minerals (Gibson, 2005; Graham et al., 2007) either at home or in factories (Brown et al., 2010) for products such as flour, bread, biscuits, etc. Vitamin A is added to several cooking oils marketed in India. Recently, iodized salt is being marketed in India to overcome iodine deficiency. Yet another approach is to improve dietary composition by adding more red meat, fruits, and green vegetables (Gibson and Anderson, 2009). The major disadvantage of these approaches is that the major beneficiaries are urban people and rural poor masses are left out in developing countries. As regards enrichment of traditional foods with minerals, this requires a large number of workers/volunteers and continuous supply of funds for demonstrations, which again may remain restricted to urban or peri-urban people. Improving dietary composition with foods richer in Fe, Zn, and vitamins requires money and in many developing countries including India, poor purchasing power of a large part of human population is a major issue (Swaminathan, 2002). Considering Fe and Zn as an important nutritional problem, specially in the developed countries (Graham, 2008), the need for genetic biofortification of cereals by developing cultivars with denser Zn (and other micronutrients) grains was mooted by Dr. Robin D. Graham of the University of Adelaide, Australia, Dr. Ross M. Welch of the U.S. Plant, Soil and Nutritional Laboratory, USDA-ARS, Ithaca, NY, USA, and Howarth, E. Bouis of the International Food Policy Research Institute, Washington, DC, USA (Bouis et al., 2011; Grahan et al., 2001). Genetic biofortification may involve both traditional breeding as well biotechnological tools. Their efforts led to the development of programs such as HarvestPlus, Golden Rice, and African Biofortified Sorghum Project, focusing on the development of crop varieties capable of producing grains denser in Zn and other micronutrients (Stein, 2010). Golden rice has been engineered to express beta carotene by introducing a combination of genes that code for biosynthesis pathway for the production of provitamin A in the endosperm (Ye et al., 2000). Enhancement of Fe content in rice has been also achieved by improving the uptake from soil and by increasing the absorption and storage of Fe (Murray-Kolb et al., 2002; Takahashi et al., 2001). Further, Genetically Modified (GM) rice has been developed that produces both beta-carotene and ferritin (Potrykus et al., 1996). However, there are problems in the acceptance of GM crops in several countries (Jaffe, 2005). A detailed discussion on this is beyond the scope of this review. There is a large genotypic variation in grain Zn concentration of modern wheat genotypes and its wild relatives (Cakmak et al., 2010a; Gome-Becerra et al., 2010a,b). Similarly in screening of close to 1000 rice genotypes at the International Rice Research Institute, Los Banos, Philippines,...