The conventional and transgenic breeding approaches for biofortification of rice grains with high fe & zn contents and enhancing their bioavailability to combat micronutrient malnutrition-a review

In the developing countries million of people are suffering from malnutrition.In these countries rice is a staple food in daily dietary system but among grains it is the poorest supplier of iron and zinc which leads to micronutrient malnutrition reducing adult productivity, causing anemia,retarding mental and physical growth. Alternative to improving malnutrition and balancing diet are supplementation chemical fortification and dietary diversification which failed to solve the problem due to high cost,limited infra structure for processing regulatory control, marketing problem of fortified food and poverty.Hence there is a need to adopt the cost effective micronutrient bio-fortification system. But Fe and Zn bio-fortification of rice grains will not be enough to satisfy the human micronutrient requirement due to the presence of the phytic acid,an antinutrient that can prevent the absorption of iron and Zinc decreasingtheir bioavailability. Although phytase is an enzyme capable of degrading phytic acid and improving bioavailability of micronutrients but its use by yeast fermentation as feed additive increases feeding cost.The improvement for iron, zinc and reduced phytic acid in rice grains will provide greater opportunity to eradicate malnutrition among poor families but greatly increasing iron levels in rice grains could result in decreased crop yield which is not acceptable to the farmers. Therefore,the identification of desirable donors containing high iron, zinc and low phytic acid and incorporating these traits into the back ground of high yielding cultivars through self sustainable and cost effective classical and transgenic breeding approach willalso provide further opportunity to develop high yielding cultivated rice varieties with high level of Fe,Zn and low phytic acid eradicating malnutrition. Agronomic management practices also influence micronutrient uptake and their accumulation in bio-fortified rice grains.