Rice Genomics and Genetics 2015, Vol.6, No.9, 1-9
4
approximately 50% of anemia in the population is
thought to be due to iron-deficiency but the
proportion may vary among population groups and
in different areas according to local conditions.
According to WHO estimates, iron deficiency is
most rampant in preschool children and pregnant
women in developing countries. Iron deficiency
results in anemia in human beings that reduce the
immune competence, impairs the body homeostasis,
affect the development brain. Billions of people are
at risk for zinc deficiency. In fact, more than
400,000 children die each year due to zinc
deficiency. Current estimates of the risk of zinc
deficiency
indica
te that approximately one-third of
the world’s population live in countries where the
risk of zinc deficiency is high. Zinc is involved in
more body functions than any other mineral. Zinc’s
role include acting as necessary component of more
than 200 enzyme systems, normal growth and
development, the maintenance of body tissues,
sexual function, and the immune system (Zimme-
rmann and Hurrell 2002).
Some 127 million preschool children are vitamin
A-deficient, which is about one-quarter of all
preschool children in high-risk regions of the
developing world (
www: unicef.org/vitamina
). Globally,
approximately 4.4 million preschool-age children
have visible eye damage due to vitamin A deficiency.
Close to 20 million pregnant women in developing
countries are also vitamin A deficient, of which
about one-third are clinically night-blind. Nearly
one-half of these cases occur in India (Flowers,
2000).
Animals, including humans, are incapable of
synthesizing 10 of the 20 amino acids needed for
protein synthesis, and these ‘‘essential’’ amino acids
must therefore be obtained from the diet (WHO,
2000). Amino acid deficiency causes the disease
“kwashiorkor”
and its symptoms include apathy,
diarrhoea, inactivity, failure to grow, and edema
(Schwartz et al. 2003).
3 Biofortification
Biofortification, which refers to the breeding of
staple plants/ foods products with high bioavailable
micronutrient content has the potential to provide
coverage for remote rural populations, where
supplementation and fortification programs may not
reach and it inherently targets the poor especially
women, infants and children who consume high
levels of staple foods and little else (Bouis et al.,
2003). Possibility of evolving micronutrient dense
crops using plant breeding and/or biotechnological
(marker assisted selection, transformation, etc.)
strategies exists within the genomes of staple food
crops (Welch and Graham, 2004). A lot of
variability does exist for micronutrient (Fe, Zn,
Vitaimin A, etc) content and bioavailability in many
crops including rice. Alternatively, several useful
genes have been identified, which may be used to
improve the nutritional quality of commercially
important cereal crops via transformation (Bouis et
al., 2003). Some of the landmark achievements in
developing nutrient-dense crops include: (i)
engineering of
β-carotene
biosynthesis pathway in
rice (Paine et al., 2005), (ii) improvement of iron
content in rice by transferring the soybean and
Phaseolus vulgaris
ferritin
genes and (iii) positional
cloning of
GPC-B1
, and a wild-wheat QTL
associated with increased grain protein, Zn and Fe
contents (Uauy et al., 2006). In addition, micronutrient
element enrichment of seeds can increase crop
yields when sowed to micronutrient-poor soils,
assuring their adoption by farmers. A comprehensive
program on “Biofortification” was started in last
century mainly under the auspices of HarvestPlus
(Pfiffer and McClafferty 2007).
4 Molecular and transgenic strategies for
improving iron and zinc content and
bioavailability in rice
Over the past few decades till 1990, most of the
breeding research was concentrated on increasing
the grain yield and to improve the resistance to
environmental stresses, pests and pathogens
(Borlaug, 2000), but little or no attention was given
towards the enhancement of its nutritional quality.
Recent developments in the area of genomics,
transformation and molecular mapping have
provided new tools for molecular dissection of
complex polygenic traits, improving our understanding
of factor regulating micronutrient efficiency, rapid
discovery of genes/ QTLs involved, marker-assisted
breeding and transfer of important genes with
potential to improve mineral density.
