Biology Reference
In-Depth Information
As outlined by Wurtzel and colleagues
(2012), efforts to increase the provitamin A
concentration in maize need to target three
potential intervention points in the carotenoid
metabolic pathway: (1) maximizing the path-
way flux through manipulation of flux deter-
minants such as PSY, CrtISO, DXS3, DXR,
HDR, and GGPPS1 (Vallbhaneni and Wurtzel
2009); (2) Optimising the provitamin A com-
position through manipulation of
LcyE
and/or
CrtRB1
(hydroxylase); and (3) minimizing the
carotenoid degradation/sequestration by manip-
ulating CCD, CrtISO, ZEP1, and ZEP2.
HarvestPlus, a multi-institutional Program on
Agriculture for Improved Nutrition and Health,
leads a global effort to develop and deliver bio-
fortified staple food crops with one or more
of the three most limiting nutrients in the
diets of the poor: vitamin A, zinc, and iron
(Brown 1991; Bouis 2010). CIMMYT leads the
HarvestPlus-Maize Program, where the primary
target is improving provitamin A concentration
in the endosperm beyond 15 μg/g. Provitamin
A biofortification of maize started seven years
ago in CIMMYT and considerable progress
has been achieved to date at CIMMYT and
IITA in active collaboration with several insti-
tutions/universities worldwide. One of the major
objectives of HarvestPlus-Mazie is to tropicalize
the high provitamin A temperate maize sources
so as to convert the popular African OPVs (open
pollinated varieties) and inbred lines into high
Provitamin A versions.
As one of the key target countries for
deployment of high provitamin A maize, the
HarvestPlus-Maize program is focusing on Zam-
bia, where the average per capita consumption
of maize is more than 130 kg per year (356 g
per day), and the vitamin A deficiency is as
high as 54% in children under the age of five,
and 13% in women aged 15-49 (WHO 2009).
The first-generation experimental hybrids devel-
oped at CIMMYT have about 6 to 9 μg/g of
ProA, and five of these hybrids were submitted to
the Zambian National Performance Trials (NPT)
during 2010-2011. In addition to provitamin A-
enriched elite germplasm development, several
ongoing activities assess and validate farmer
and consumer acceptance of these promis-
ing hybrids, and have begun creating interest,
demand, and supply for seed of the best hybrids.
It is expected that the best one or two hybrids
will be formally released for commercialization
and planting in 2012/2013. With the discovery
of useful allelic diversity for
LcyE
and
CrtRB1
and development of molecular markers, source
lines with
>
15 μg/g of provitamin A carotenoids
have been identified and are now routinely used
as parents for new crosses at CIMMYT. This
has led to the selection of lines with 40-250%
higher provitamin A carotenoid concentrations
than lines without the favorable allele.
Another improvement in the breeding pro-
gram was achieved by using UPLC (Ultra-
Performance Liquid Chromatography) in place
of HPLC (High-Performance Liquid Chro-
motography) for carotenoid screening, which
greatly increased the number of samples of provi-
tamin A that could be evaluated and allowed
selection for this trait earlier in the breeding
pipeline. The big challenge is to ensure that new
biofortified varieties are competitive for all the
crucial traits, including seed production, food
processing quality, taste, and other characteris-
tics that determine acceptability to farmers and
consumers.
KernelFe and Zn-richMaize for
Alleviating “Hidden Hunger”
Micronutrient malnutrition, popularly called
“hidden hunger,” is one of the alarming prob-
lems in the developing world, afflicting an
estimated 3 billion people (UNSCN 2004).
Fe-related deficiencies affect cognitive devel-
opment, growth, reproduction, and produc-
tivity (Bouis 2002). Zn deficiency leads to
anorexia, depression, impaired growth and
development, altered reproductive biology, gas-
trointestinal problems, and impaired immunity,
and affects 49% of world population (Solomons
2003). Accordingly, understanding the genetic
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