Biofortification is an upcoming, promising, cost-effective, and sustainable technique of delivering micronutrients to a population that has limited access to diverse diets and other micronutrient interventions. Unfortunately, major food crops are poor sources of micronutrients required for normal human growth. The manuscript deals in all aspects of crop biofortification which includes-breeding, agronomy, and genetic modification. It tries to summarize all the biofortification research that has been conducted on different crops. Success stories of biofortification include lysine and tryptophan rich quality protein maize (World food prize 2000), Vitamin A rich orange sweet potato (World food prize 2016); generated by crop breeding, oleic acid, and stearidonic acid soybean enrichment; through genetic transformation and selenium, iodine, and zinc supplementation. The biofortified food crops, especially cereals, legumes, vegetables, and fruits, are providing sufficient levels of micronutrients to targeted populations. Although a greater emphasis is being laid on transgenic research, the success rate and acceptability of breeding is much higher. Besides the challenges biofortified crops hold a bright future to address the malnutrition challenge.

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Biofortified Crops Generated by Breeding, Agronomy, and Transgenic Approaches Are Improving Lives of Millions of People around the World

Meeting human needs within the ecological limits of our planet calls for continuous reflection on, and redesigning of, agricultural technologies and practices. Such technologies include fertilisers, the discovery and use of which have been one of the key factors for increasing crop yield, agricultural productivity and food security. Fertiliser use comes, however, at an environmental cost, and fertilisers have also not been a very economically effective production factor to lift many poor farmers out of poverty, especially in African countries where application on poor soils of unbalanced compositions of nutrients in fertilisers has shown limited impact on yield increase. Agronomic practices to apply existing mineral fertilisers, primarily containing N, P and K, at the right time, the right place, in the right amount, and of the right composition can improve the use efficiency of fertilisers. However, the overall progress to reduce the negative side effects is inadequate for the desired transformation toward sustainable agriculture in poor countries. Globally, there have been no fundamental reflections about the role and functioning of mineral fertilisers over the past 5 decades or more, and compared to other sectors, dismal investments have been made in mineral fertiliser research and development (R&D). In this paper, we reflect on current fertilisers and propose a more deliberate adoption of knowledge of plant physiological processes—including the diversity of mineral nutrient uptake mechanisms, their translocation and metabolism—as an entry point in identifying the physicochemical “packaging” of nutrients, their composition, amount and timing of application to meet plant physiological needs for improved instantaneous uptake. In addition to delivery through the root, we suggest that efforts be redoubled with several other uptake avenues, which as of now are at best haphazard, for the delivery of nutrients to the plant, including above ground parts and seed coating. Furthermore, ecological processes, including nutrient-specific interactions in plant and soil, plant-microorganism symbiosis, and nanotechnology, have to be exploited to enhance nutrient uptake. It is hoped that concerted R&D efforts will be pursued to achieve these strategies.

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Revisiting fertilisers and fertilisation strategies for improved nutrient uptake by plants

Zinc (Zn) is one of the most essential micronutrients required for the growth and development of human beings. More than one billion people, particularly children and pregnant women suffer from Zn deficiency related health problems in Asia. Rice is the major staple food for Asians, but the presently grown popular high yielding rice varieties are poor supplier of Zn in their polished form. Breeding rice varieties with high grain Zn has been suggested to be a sustainable, targeted, food-based and cost effective approach in alleviating Zn deficiency. The physiological, genetic and molecular mechanisms of Zn homeostasis have been well studied, but these mechanisms need to be characterized from a biofortification perspective and should be well integrated with the breeding processes. There is a significant variation for grain Zn in rice germplasm and efforts are being directed at exploiting this variation through breeding to develop high Zn rice varieties. Several QTLs and gene specific markers have been identified for grain Zn and there is a great potential to use them in Marker-Assisted Breeding. A thorough characterization of genotype and environmental interactions is essential to identify key environmental factors influencing grain Zn. Agronomic biofortification has shown inconsistent results, but a combination of genetic and agronomic biofortification strategies may be more effective. Significant progress has been made in developing high Zn rice lines for release in target countries. A holistic breeding approach involving high Zn trait development, high Zn product development, product testing and release, including bioefficacy and bioavailability studies is essential for successful Zn biofortification.

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Advances in breeding for high grain Zinc in Rice.

In this review, we examine the potential of Zn-enriched fertilisers to alleviate human dietary Zn deficiency The focus is on ten African countries where dietary Zn supply is low and where fertiliser subsidies are routinely deployed on cereal crops Dietary Zn supply and deficiency prevalence were quantified from food supply and composition data Typical effects of soil (granular) and foliar Zn applications on Zn concentrations in maize (Zea mays L), rice (Oryza sativa L) and wheat (Triticum aestivum L) grains were based on a systematic literature review Reductions in disease burdens attributable to Zn deficiency and cost-effectiveness were estimated using a disability-adjusted life years (DALYs) approach Baseline Zn supply in 2009 ranged from 71 (Zambia) to 119 (Mali) mg capita
 −1 day−1; prevalence of Zn deficiency ranged from 24 (Nigeria) to 66 % (Zambia) In reviewed studies, soil Zn application led to an increase in median Zn concentration in maize, rice and wheat grains of 23, 7 and 19 %; foliar application led to increases of 30, 25 and 63 % Enriching granular fertilisers within current subsidy schemes would be most effective in Malawi, reducing DALYs lost due to Zn deficiency by 10 % The cost per DALY saved ranged from US$ 624 to 5893 via granular fertilisers and from US$ 46 to 347 via foliar fertilisers Foliar applications are likely to be more cost effective than soil applications due to fixation of Zn in the soil but may be more difficult to deploy Zinc fertilisation is likely to be less cost-effective than breeding in the longer term although other micronutrients such as selenium could be incorporated

https://link.springer.com/content/pdf/10.1007%2Fs11104-015-2430-8.pdf

Zinc-enriched fertilisers as a potential public health intervention in Africa

Rice (Oryza sativa L.), wheat (Triticum aestivum L.) and common bean (Phaseolus vulgaris L.) are major staple food crops consumed worldwide. Zinc (Zn) deficiency represents a common micronutrient deficiency in human populations, especially in regions of the world where staple food crops are the main source of daily calorie intake. Foliar application of Zn fertilizer has been shown to be effective for enriching food crop grains with Zn to desirable amounts for human nutrition. For promoting adoption of this practice by growers, it is important to know whether foliar Zn fertilizers can be applied along with pesticides to wheat, rice and also common bean grown across different soil and environmental conditions. The feasibility of foliar application of zinc sulphate (ZnSO4.7H2O) to wheat, rice and common bean in combination with commonly used five fungicides and nine insecticides was investigated under field conditions at the 31 sites-years of seven countries, i.e., China, India, Pakistan, Thailand, Turkey, Brazil and Zambia. Significant increases in grain yields were observed with foliar Zn/foliar Zn + pesticide (5.2–7.7 % of wheat and 1.6–4.2 % of rice) over yields with no Zn treatment. In wheat, as average of all experiments, higher grain Zn concentrations were recorded with foliar Zn alone (41.2 mg kg−1) and foliar Zn + pesticide (38.4 mg kg−1) as compared to no Zn treatment (28.0 mg kg−1). Though the magnitude of grain Zn enrichment was lesser in rice than wheat, grain Zn concentrations in brown rice were significantly higher with foliar Zn (24.1 mg kg−1) and foliar Zn + pesticide (23.6 mg kg−1) than with no Zn (19.1 mg kg−1). In case of common bean, grain Zn concentration increased from 68 to 78 mg kg−1 with foliar Zn alone and to 77 mg kg−1 with foliar Zn applied in combination with pesticides. Thus, grain Zn enrichment with foliar Zn, without or with pesticides, was almost similar in all the tested crops. The results obtained at the 31 experimental site-years of seven countries revealed that foliar Zn fertilization can be realized in combination with commonly-applied pesticides to contribute Zn biofortification of grains in wheat, rice and common bean. This agronomic approach represents a useful practice for the farmers to alleviate Zn deficiency problem in human populations.

D. Grewal

Papers

Contrasting grain-Zn response of biofortification rice (Oryza sativa L.) breeding lines to foliar Zn application