Authors: Vikas Gupta, Satish Kumar, CN Mishra and RP Meena
Malnutrition, including both nutrient deficiencies as well as diet related chronic diseases (e.g., diabetes, stroke, cancer), is responsible for more than twenty million mortalities annually. Micronutrient malnutrition alone affects more than two billion people, mostly among resource poor families in developing countries, with Fe, Zn, I and Vit. A deficiencies most prevalent. Malnutrition contributes to anaemia (due to iron deficiency), blindness (Vit A deficiency), cretinism and goitre (due to Iodine deficiency) and immune dysfunctioning, impaired growth (Zinc deficiency). Micronutrient deficiency, especially of iron and zinc, is a global problem that affects more than one third of the world population in developing as well as in industrialized countries. Trace elements are always present in the soil and although they are limiting for plant production, their uptake, transport and storage in plants are not well understood. All cereals, including rice as the most important staple crop, contain only low levels of micronutrients. Mineral deficiency in staple food crops such as rice and wheat in Asia, Maize in Sub-Saharan Africa and Latin America is very low. Out of 22 minerals required by human beings for normal growth, dietary deficiencies of Fe, and Zn are the most and wide spread. Losses in processing and their reduced availability due to the presence of anti nutritional factors such as phytic acid, tannins, lignins and food fibres further aggravate the problem. About 60-80% of the world’s population suffers from Fe and >30% from Zn deficiency. To meet recommended dietary allowance (RDA) demand for Zn and Iron consumption cereal grains should contain around 40-60mg/kg but the current level in cereals is 10-30mg/kg. The adage comes from the farm not the pharmacy, is at the heart of ongoing international biofortification research and breeding programmes. There are many strategies to alleviate micronutrient deficiency including:
a. Supplementation: nutrients directly given in the form of syrups or pills.
b. Dietary diversification: production and consumption of a wide variety of foods.
c. Fortification: using commonly consumed widely accessible foods to deliver one or more nutrients.
d. Agronomic fortification: enrichment of nutrients by fertilizer application.
e. Bioavailability: enhanced bioavailability at the existing and biofortified levels.
f. Biofortification: Genetic enhancement of nutritious status of crop cultivars.
Among various strategies, biofortification approach for high mineral content in grains is considered most suitable and cost effective. Biofortification is the development of micronutrient dense staple food crops using best traditional practices and modern biotechnology. Biofortication is different from Industrial fortification as biofortification relies on the biosynthetic and physiological capabilities of plants to produce and accumulate desired nutrients in the edible plant parts. Biofortification is a scientific method for improving the nutritional value of foods already consumed by those suffering from hidden hunger. Plant breeders first have to look for the sources and using them in breeding to develop crops with improved nutritional value. Malnourished communities receive these biofortified crops to grow and eat. When consumed daily, biofortified foods contributes to body stores of micronutrients throughout their life cycle.
Biofortification:
a. Plant Breeding perspective
Biofortification through cultivar selection and breeding is an important approach to both adequacy and quality of the human diet. There is a potential to increase the micronutrient density of staple foods by conventional breeding. Crop plants often show genetic variation in essential nutrient content, which then allows breeding programs to be used to improve the levels of minerals and vitamins in crops. The existence of a large and useful genetic variation is of great importance for a successful breeding program aiming at improving cereal grains with micronutrients. Moreover, micronutrient-density traits are stable across environments. It is also possible to combine the high-micronutrient-density trait with high yield in most crops. Substantial genetic variation for Fe, Zn and Vit A has been found in cereals e.g., four-fold variation has been reported in Fe and Zn levels in different rice genotypes, 2-3 fold variation for Fe & Zn in different Aegilopes species and up to 6.6-fold variation in beans and peas. However, the genetic variation in micronutrient concentration of modern cultivated wheat is fairly limited. Compared to modern wheat, the primitive spelt wheat possesses a higher genetic variation in protein and micronutrients, suggesting that it is a potential source for breeding biofortified (micronutrient-dense) modern cultivars. In addition, synthetic wheats derived from Aegilops tauschii also have a high genetic potential for increasing grain Zn concentration of cultivated wheat. Once the plants have been enriched with micronutrients, it is also possible to improve both their vitality and the nutrient quality simultaneously. To date, orange-flesh sweet potato lines with high levels of Beta -carotene (over 200 ug/g) have been identified and beans with improved agronomic traits and grain type and 50-70% more Fe have been bred through conventional means. Therefore, it will be possible to improve the content of several limiting micronutrients together, thus pushing the population towards nutritional balance.
b. Molecular breeding perspective:
The micronutrient (Fe & Zn) content in the cultivated wheat germplasm is very low, in the range of 10-30 mg/kg. But a wide variation for these micronutrients is available in wild Aegilopes species. These wild species are used to introgress these useful traits using recurrent backcrossing. Selection of the lines carrying high micronutrients can be selected. Another technique of recombination or radiation induced transfer of critical chromatin with reduced linkage drag can be achieved.once these traits got transferred, then molecular characterization can be done using anchpored SSR markers. Further insitu hybridization for chromatin identification can be done using different hybridization techniques. Several QTLs have been mapped from different Ae. Species and have been transferred into cultivated background.
c. Biotechnology Perspective:
In the absence of genetic variation in nutrient content among varieties, transgenic approaches can be a valid alternative for crop improvement. These approaches are necessary in some cases and potentially advantageous in others when compared with conventional breeding. The best-known example is golden rice; Beta -carotene has not been identified in the endosperm of any rice variety and an advanced transgenic line, containing 37 ug/g carotenoid, of which 31 ug/g is Beta -carotene, is now available. The rapid identification and characterization of gene function and the utilization of these genes to engineer plant metabolism has been a driving force in recent biofortification efforts. Wild durum (pasta) wheat has shorter grain maturation periods and higher protein, Zn and Fe content as compared to domesticated wheats. The domesticated wheats have an inactive form of the gene when compared with wild durum wheat, thus explaining their lower nutrient content relative to the wild durum wheat. The active version can now be incorporated by breeding or genetic engineering to increase the protein, Zn and Fe content of domesticated wheats.
HarvestPlus:
HarvestPlus is a Challenge Program of the Consultative Group on International Agricultural Research (CGIAR) under the leadership of the International Center for Tropical Agriculture (CIAT) and the International Food Policy Research Institute (IFPRI), leading global program aimed at improving staple food crops with Zn, Fe and VA by using plant breeding strategy. HarvestPlus is currently collecting data on retention of the nutrient following processing and cooking, bioconversion/bioavailability and nutrient requirements. Recently, a global zinc fertilizer project has been initiated under HarvestPlus program. This project aims at evaluating the potential of Zn-containing fertilizers for increasing Zn concentration of grains and improving crop production in different target countries. Through a global alliance now involving more than two hundred scientists, HarvestPlus is biofortifying seven staple food crops (Table 1) which are critical in the diets of the poor in developing countries.
Table 1: HarvestPlus target crops and nutrients
| S. No | Crop name | Nutrient | S. No | Crop name | Nutrient |
| 1 | Sweet potato | Provitamin A | 5 | Wheat | Zinc |
| 2 | Cassava | Provitamin A | 6 | Bean | Iron |
| 3 | Maize | Provitamin A | 7 | Pearl millet | Iron |
| 4 | Rice | Zinc |
Advantages:
a. Biofortification capitalizes on the regular daily intake of a constituent and large amount of food staples are consumed by all, targeting low income thresholds.
b. It is one time investment to develop nutrient rich seeds. Recurrent costs are low in producing seed and seeds can be shared across nations.
c. Biofortification is sustainable as nutritionally improved varieties can begrown year after year.
d. Biofortified seeds are accessible to resource poor farmers.
Challenges:
a. Addition of one breeding objective to breeding programme.
b. Amount of nutrients in the new food crops is low as compared to the fortified and supplemented.
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