Molecular Mapping of High Iron and Zinc Rich Regions in Rice (Oryza sativa L.) Grains Using Microsatellite Markers

Author Name(s): *P. Nagesh , G. Usharani, C. N. Neeraja, V. Ravindra Babu, T. Dayakar Reddy
Author Email: patnenagesh@gmail.com

Abstract

Rice (Oryza sativa L.) is a primary source of food for billions of people throughout the world, yet it contains insufficient levels of the key micronutrients iron, zinc and vitamin A to meet the daily dietary requirements. Biofortification of staple food crops has thus been considered a sustainable strategy to overcome the problem of micronutrient deficiencies prevalent in rice. The present investigation was conceptualized with the prime objective of mapping the chromosomal regions associated with high iron and zinc content involving the F2 populations derived from the cross of Swarna with Madhukar for high iron and zinc content using microsatellite markers derived from the genomic regions associated with iron and zinc metabolism. Three polymorphic markers viz., SC 120, SC 128 and SC129 were identified which were unlinked and hence single marker analysis was done to check the association of the marker with the trait. SC129 showed highest significant variation with both iron and zinc at the tune of R2=13.09% and R2= 19.51%, respectively. The association could be made more stringent by further analysis of more number of lines and using more number of markers.

Keywords

Biofortification, Iron, Mapping, Zinc

Introduction

Rice (Oryza sativa L.) occupies the enviable prime place among the food crops cultivated around the world. It is known as the grain of life and is synonymous with food for Asians as it supplies majority of starch, protein and micronutrient requirements [1], [2]. Poor grain micronutrient contents (iron, zinc and pro-vitamin A) in cereals is the primary cause of prevalent nutritional deficiency related disorders amongst population having cereals based diet, especially those dwelling in developing world[3]. Rice scientists have long recognized its micronutrient deficiencies, which are the basis of numerous human health problems worldwide. Mineral nutrient deficiencies have egregious societal costs including learning disabilities among children, increased morbidity and mortality rates, lower worker productivity and added high health care costs, all of which diminish human potential, felicity and national economic development[4], [5]. Malnutrition has been a serious problem in the developing world mostly in South and South East Asia and Sub Saharan Africa [6]. Over three billion people suffer from micronutrient malnutrition [7]. In the last two decades, new research findings generated by the nutritionists have brought to light the importance of vitamins, minerals and proteins in maintaining good health, adequate growth and even acceptable levels of cognitive ability apart from the problem of protein energy malnutrition. Rice is a predominant staple food and a major source of dietary carbohydrate for more than half of the world’s population [8]. In order to enhance the micronutrient concentration in the rice grain, suitable breeding programmes should be followed. In recent years, attention has turned towards strategies for improving human vitamin and mineral nutrition, especially iron, zinc, selenium and iodine [9], [10]. Although, rice is not a major source of mineral in the diet, any increase in its mineral concentration could significantly help to reduce iron and zinc deficiency because of the high levels of rice consumption in Asia [11].
Even though the levels of carbohydrates are adequate in rice, parallel analysis of the levels and bioavailability of the other micronutrients in rice revealed that the levels are very low and consumption of rice alone cannot meet the recommended daily allowance for a range of vitamins, minerals and proteins. To overcome this, a genetic approach called Biofortification [12] has been developed, which aims at biological and genetic enrichment of food stuffs with vital nutrients. Biofortification of staple food crops for enhanced micronutrient content through genetic manipulation is the best option available to alleviate hidden hunger with little recurring costs [4], [13]. Ideally, once rice is biofortified with vital nutrients, the farmer can grow the variety indefinitely without any additional input to produce nutrient packed rice grains in a sustainable way. This is also the only feasible way of reaching the malnourished population in rural India.

Conclusion

The genetic modifications offer good opportunities to increase the iron and zinc content in rice grains. Biofortification is being projected as one of the sustainable and feasible key strategy for addressing the hidden malnutrition across the world. The markers identified could be used as a tool for identifying and mapping of new high iron and zinc content genes. The association could be made more stringent by further analysis of more number of lines and using more number of markers. The knowledge of QTL analysis and the information of DNA in identified genes on mineral accumulation is helpful for the identification of interesting alleles of relevant genes. Further studies have to be conducted to know the genetics involved in the inheritance of high iron and zinc density in rice grains and pertinently the breeding strategies are to be formulated.

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