Poverty, hunger and malnutrition were the major pre-green revolution problems in India. But, Indian Agriculture has made impressive progress over the years and phenomenal growth has been observed in crop production. Divine grace of green revolution has reduced hunger problem because of its fivefold increased production of food grains. However, still 21.9 per cent of population is in extreme poverty and 15.2 per cent of people are malnourished. Globally, around two billion people suffer from malnutrition, while 815 million people are undernourished (Anon., 2017). Now, the major issue of growing population of the country is malnutrition. Malnutrition is the most common nutritional disorder caused due to inadequate consumption of balanced diet and it poses serious socio-economic implication in developing and underdeveloped countries. As per the National Family Health Survey-4 (2015-16), 38.4 per cent of the Indian children (<5 yr) are stunted, 21.0 per cent are wasted and 35.7 per cent of the children are underweight. Anemia is also a serious health issue, where 58.4 per cent of the Indian children (6-59 months) and 53 per cent of the adult women (15-49 year) are affected from this deficiency (Anon., 2017). The figure is also alarming among adult males as 22.7 per cent were found to be anemic. Apart from this, around two billion people across the world suffer from another type of hunger known as “hidden hunger,” which is caused by an inadequate intake of essential micronutrients in the daily diet. Out of the 17 Sustainable Development Goals of global community, 12 are highly linked to nutrition thereby; signifying the role of nutrition in building healthy society and successful nation. Hence, need of the hour is to deliver more nutritious food to malnourished population in order to forbid the malnutrition and hidden hunger. The Sustainable Development Goals is also emphasizing reduction of malnutrition and hidden hunger (Shubha et al., 2020).

 Tackling malnutrition

                Malnutrition refers to deficiency, excess or imbalanced intake of protein, energy, vitamins and mineral nutrients. Malnutrition or hidden hunger can be overcome by nutritional supplementation. There are many different strategies or methods that are followed for nutritional supplementation like dietary diversification, medical supplementation, commercial fortification and crop bio-fortification. The most desirable approach is to increase the diversity of food intake which is referred as ‘dietary diversification’. However, practicing dietary-diversification may not be feasible in many developing countries which are having low-income. Medical supplementation deals with the addition of nutrients artificially, either by providing supplements such as vitamin A and iron pills/capsules. Further, adding the nutrients in basic food products such as iodized salt, Iron- and folate-fortified flour and vitamin A added cooking oil is food/commercial fortification. Bio-fortification is a sustainable approach where nutritional profile of staple food crops is increased. However, each of these above mentioned methods is effective under ideal situations but ‘bio-fortification’ remains the most sustainable and cost-effective mean for providing the desired levels of nutrients through diet in a natural form (Hotz, 2013).

 Bio-fortified crops

                Bio-fortification is the process by which the nutrient content of the edible portion of food crops is deliberately increased through conventional plant breeding, and/or improved agronomic practices and/or modern biotechnology without sacrificing any characteristic that is preferred by consumers or most importantly to farmers. It is the food-based strategy to reduce micronutrient malnutrition in low-income populations by means of the large-scale introduction of bio-fortified staple food crops and varieties. Bio-fortification of crops is also recognized as a nutrition-sensitive-agriculture intervention which can reduce vitamin and mineral deficiency (Nestel et al., 2006). Concentrated efforts of Indian Council of Agricultural Research, State Agriculture Universities and other Research Institutes (ICRISAT and BARC etc.) have led to phenomenal result in developing and releasing bio-fortified varieties in several crops (Yadav et al., 2020).  Currently, rice, wheat, maize, pearl millet, finger millet, small millet, lentil, groundnut, linseed, cauliflower, potato, sweet potato, greater yam and pomegranate are bio-enriched for nutritional factors (protein, iron, zinc, lysine, tryptophan, provitamin-a, vitamin-c, β-carotene, oleic acid, linoleic acid and anthocyanin) and crops like mustard and soybean are impoverished for anti-nutritional factors (erucic acid, glucosinolates, kunitz trypsin inhibitor and lipoxygenase). Several examples of bio-fortified crops and cultivars with their fortified nutritional or anti-nutritional factors are given in the Table 1.

 Methods of crop bio-fortification

                Bio-fortification of essential micronutrients into crop plants can be done through various processes, including conventional breeding, genetic engineering, mutational breeding and agronomic approaches. Conventional breeding has gained major focus of researchers for developing bio fortified food crops (Yadav et al., 2018). Conventional plant breeding involves cross pollination between two plants which are genetically close relatives, to induce sexual recombination with the aim of producing new plants with favourable selected traits. Whereas, genetic engineering involves insertion of selected genetic material, derived from a different species or organism, into the genetic material of the plant with the aim of producing a novel, desired trait in the plant. This procedure can be followed by conventional plant breeding. Mutational breeding refers to a two-step process by which induced mutagenesis is followed by conventional plant breeding to produce plants with desired traits. Mutagenesis refers to the process by which mutations in the genetic material of plants are induced using chemicals or radiation to result in new, desired traits in the plant. Agronomic fortification can be achieved through soil application, foliar application or by addition of nutrients to irrigation water. This approach remains limited to a few trace elements including iodine, selenium, iron and zinc, which are deficient in the soils of some geographical regions.

Advantages and limitations of Biofortification

                Bio-fortification has its upper hand towards advantages over disadvantages. Bio-fortification is  targeted primarily to the rural poor who rely heavily on  locally produced staple foods as their primary source of nutrition and who often have restricted financial or market access to commercially processed fortified foods. This also puts a solution in the hands of farmers, combining the micronutrient trait with other agronomic and consumption traits that farmers prefer. Target micronutrient levels for bio-fortified crops are set to meet the specific dietary needs of women and children, based on existing consumption patterns. After fulfilling the household’s food needs, surplus bio-fortified crops make their way into rural and urban retail outlets. Bio-fortification is long-term and cost-effective in nature when compared to other methods of nutritional supplementation. Bio-fortified crops are also a feasible means to reach rural populations who may have limited access to diverse diets or other micronutrient interventions. Seeds rich in trace elements are stronger to resist against biotic and abiotic stresses including diseases and environmental stresses. Fortified or enriched seeds also have more plant vigour, seedling survival, faster initial emergence and grain yield. However, there are few limitations to bio-fortification methods like conventional breeding and agronomic approaches such as the detrimental effects of fertilizers on the environment, if misused, or the limited genetic variation present in some crops. These limitations dampen the efficacy and application of bio-fortification methods globally. Additionally, bio-fortified foods are generally limited in the amount and range of micronutrients. Further, anti-nutritional compounds such as phytic acid and tannins are the limiting factors which inhibit the absorption of minerals (Fe, Zn, and Ca) in the gut.

Table 1. Nutritional and anti-nutritional factors of biofortified crops and cultivars