I. INTRODUCTION
Micronutrient malnutrition is recognized as a massive and rapidly growing public health issue especially among poor people living on an unbalanced diet
dominated by a single staple grain such as rice. Among the major micronutrient deficiencies common in rice-consuming countries are: iron and zinc deficiencies.
It is estimated that more than 3 billion people in the developing world are iron deficient. The problem for women and children is more severe because of their
physiological need. Iron deficiency during childhood and adolescence impairs physical growth, mental development and learning capacity. On the other hand in
adults, it reduces the capacity to perform physical tasks. Billions of people are at risk for zinc deficiency. Zinc deficiency is more extensive in developing countries
where more than 60 per cent of the population is at risk www.harvestplus.org. Zinc is a component of more than 300 enzymes that are needed to repair wounds,
maintain fertility, synthesize protein, and boost immunity among many functions important in human health. Symptoms of zinc deficiency are subtle and often
include stunted growth, eczema, hair loss, delayed sexual maturation and impaired mental development Mares-Perlman et al. 1995. The cost of micronutrient
deficiencies in terms of lives lost and quality of life are enormous. Some strategies to address micronutrient deficiencies include
supplementation and fortification which are continuing to address this problem. However, breeding staples such as rice with high micronutrient content dubbed as
‘biofortification’ has evolved as a new strategy to address micronutrient malnutrition. Biofortification provides a cost effective and sustainable solution to
combat malnutrition Bouis 2004. Since the poor in many low-income Asian countries consume large amounts of rice, improving its micronutrient content for
these two micronutrients shall address to a large extent the micronutrient deficiency-induced health problems.
Genetic variation for iron and zinc in the polished rice grains beras sosoh, Indonesian has been reported by Virk et al. 2006; 2007. However, genetics of
grain iron and zinc content is not known which is a prerequisite for designing efficient breeding strategies aimed at improving nutritional quality of rice.
The recent development of DNA markers in rice has provided powerful tools in assessment of genetic variation. Microsatellite markers are the markers of
choice for many breeding and genetic applications including assessment of genetic diversity because of several reasons such as abundance, higher degree of
polymorphism, cost-effectiveness, codominance and wide genomic distribution among others Panaud et al. 1995, Akagi et al. 1996, Lapitan et al. 2007 and
Edwards McCouch 2007. Furthermore, a saturated map of SSR Simple Sequence repeats markers in rice with 2240 validated and another
52,845 SSR markers is available McCouch et al. 2002 and
Zhang et al. 2007. In the present study promising germplasm possessing high zinc and iron
content along with some nutritionally rich Korean cultivars and some popular indica rice varieties were analyzed using SSR markers and selected parents were
used to develop mapping populations aimed at studying the genetic control of these traits.
Objectives of the study were to:
• Assess molecular diversity for grain nutritional traits among promising germplasm.
• Identify suitable parents for developing mapping populations • Map QTLs Quantitative Trait Loci for iron and zinc contents in polished
rice grain. • map QTLs for some agronomic and yield related traits.
Hypotheses:
• Existence of ample molecular variation in the materials used in this study. • Polymorphic SSR markers are widely distributed on the rice genome, suitable
for QTL mapping studies. • Quantitative Trait Loci for grain iron and zinc contents in polished rice grains
exist. • Quantitative Trait loci for agronomic traits and yield related traits segregate
in mapping populations for conducting QTL mapping studies.
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II. REVIEW OF LITERATURES 2.1.
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