Integrated Approach for Fe and Zn Biofortification in Wheat
Global population is increasing at an alarming rate which is expected to be around 9.2 billion by 2050 from the existing 7.2 billion. This demands for 28% higher global wheat production from the current level of production (670mt) to feed world hunger. Wheat being one of the staple food crops, serves important source of protein and energy worldwide. Fe (Iron) and Zn (Zinc) is deficient in pre-school children and pregnant women mainly in African and Asian countries which is major cause of death. Fortification, industrial supplements, dietary variation and biofortification are the major ways to get rid of micronutrient malnutrition. Amongst them, biofortification is one of the most in-expensive means to reach to the Fe and Zn deficient population of world. Genetic engineering and breeding coupled with fertigation are the only means to take care of this problem. Due the genome complexity of wheat owing to its polyploidy nature, it has been very difficult to breed and manipulate genes to develop cultivars with enriched Fe and Zn in-vivo. In the recent past, extensive biotechnological work has been done in other cereals (rice, barley, maize) which have generated wealth of information regarding mechanism of uptake, absorption and mobilization of Fe and Zn into edible part which need to be translated into wheat urgently. Harvest-Plus has taken great initiation to exploit the existing genetic diversity of many crops such as sorghum, rice, pearl millet etc. to breed for enriched Fe and Zn.
Genetic biofortification is a strategy that uses plant breeding techniques to produce staple food crops with higher micronutrient levels, reducing levels of anti-nutrients and increasing the levels of substances that promote nutrient absorption. It offers a sustainable solution to malnutrition problems by exploring natural genetic variation to develop mineral-dense crop varieties. Plant breeders screen existing accessions in global germplasm banks to determine whether sufficient genetic variation exists to breed for a particular trait. They then selectively breed nutritious cultivars of major staples, rich in Zn and Fe concentrations and with substances that promote the bioavailability of Zn and Fe. Some of the strategies which could be used for wheat biofortification in an integrated manner are 1.Germplasm screening; 2. Breeding target and target population; 3. Breeding strategies; 4. Precision phenotyping; 5. High throughput screening methodology; 6. Genotype X environment (G X E) interaction; 7. Gene discovery. In addition, agromic biofortification is another area which should be coupled with other approaches. Increasing bioavailability of the Fe and Zn is one other area to be considered.
Biofortification of cereals is the most promising intervention to overcome iron and zinc malnutrition due to its cost-effectiveness. Bioavailability of iron and zinc from cereal grains can be increased by genetic interventions by modulating accumulation of either anti-nutrient agents or prebiotics. Encouraging results have been obtained in this regard in model experimental subjects like Caco-2 cell lines, but studies involving human beings as subjects are largely lacking, thus making it difficult to realistically assess the success of this approach. Enhanced accumulation of iron and zinc in cereal grains can be achieved by fertilization or genetically manipulating iron and/or zinc homeostasis-related genes. However, it is not fully known whether it is feasible to increase the accumulation of these minerals up to desired levels in the edible parts of cereals by these strategies under field conditions. Moreover, it is not clearly identified how agronomic or genetic biofortification interventions affect the accumulation of toxic heavy metals such as cadmium and arsenic in edible portions of cereal grains. Future research should involve analyzing the accumulation of iron and zinc, as well as other heavy metals, in the edible parts of cereal grains rather than whole grains. It is also advised that the impact of genetic modifications on the agronomic performance of crops, including grain yield, drought tolerance, insect resistance, disease resistance, and so on should also be assessed. In addition, the focus should be on studies involving field crop trials and human beings as experimental subjects to analyze the effectiveness of agronomic or genetic biofortification.
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