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February, 2007
Source:
CIMMYT E-News, vol 4 no. 2 - February 2007
http://www.cimmyt.org/english/wps/news/2007/feb/formSuccess.htm
 Formula
for success
Breeding
knowledge combined with cutting-edge laboratory analysis will
produce maize rich in vital nutrients.
“The link between
agriculture and nutrition is surprisingly under-explored,” says
Kevin Pixley, who manages the Biofortified Maize for Improved
Human Nutrition project at CIMMYT. “Agricultural approaches have
the potential to alleviate micronutrient deficiencies, more
cheaply and reliably than food supplements.” The effect is
potentially far-reaching: maize is the preferred staple food of
more than 1.2 billion people in Sub-Saharan Africa and Latin
America. However, maize-based diets, particularly those of the
very poor, often lack essential vitamins and minerals. Over 50
million people in these regions are vitamin A deficient, which
can lead to visual impairments, blindness and increased child
mortality.
Pixley’s project
aims to develop varieties of maize that combine high provitamins
A, iron and zinc contents with superior agronomic qualities, and
disseminate them in partner countries in Africa and Latin
America. It is part of HarvestPlus, an international,
interdisciplinary program to alleviate nutritional deficiency
through breeding micronutrient-enriched staple foods.
 The
white maize eaten in much of sub-Saharan Africa contains almost
no provitamins A, while standard yellow maize varieties contain
about 2 micrograms per gram (µg/g)—still insufficient in a diet
dominated by maize. The good news is that there is tremendous
genetic variation in maize resulting in variable concentrations
of provitamins A. The project has been screening maize samples,
looking for the best provitamins A content. The team has now
exceeded the HarvestPlus program’s intermediate target for maize
of 8 µg/g with its current best materials; scientists anticipate
producing materials with the ultimate target of 15 µg/g within
the next four years by using cutting edge lab tools to help
select the best materials for breeding.
The breeding work
at CIMMYT is focusing on increasing the concentration of
provitamins A in maize. Open-pollinated varieties (OPVs) are
being developed using popular varieties grown in partner
countries and source materials high in provitamins A, including
synthetic varieties (generated through crosses with wild
relatives). In addition, the project team is developing inbred
lines with high provitamins A content, based on elite African
and Mexican germplasm, which will be freely available to
partners for use in producing their own enriched hybrids or
OPVs. Providing source materials to other programs is a key part
of the project, particularly to key partners Brazil, Ethiopia,
Ghana, Guatemala and Zambia, where their performance is tested
in local agro-environments
This work to
generate enhanced maize lines relies on accurate measurements of
the micronutrient contents of breeding materials at every stage.
Therefore, a major aspect of the project has been experimenting
with techniques for analyzing carotenoids (which include
provitamins A), iron, and zinc.
Carotenoids are a
particular challenge to work with, as they are very sensitive to
both light and oxygen, making samples vulnerable and difficult
to store. Maize nutritional quality specialist Natalia Palacios
and her team have adapted and perfected protocols for analyzing
carotenoid content using high performance liquid chromatography
(HPLC), in collaboration with others in the HarvestPlus network,
HPLC is very precise, but it is also expensive and
time-consuming: the samples must be extracted and immediately
analyzed overnight.
The team has
therefore taken delivery this month of new equipment to measure
near-infrared reflectance (NIR). This infrared technique is both
accurate and rapid. Collaboration with the International Potato
Centre (CIP) has shown that different carotenoid compounds can
successfully be differentiated using NIR. The next step for the
team is a big push to build on this work. “For us it is a great
challenge, and an opportunity to support and enhance the
breeding work by providing more and faster information at a
lower cost,” says Palacios. The team believes that NIR will
multiply their screening potential dramatically: last year they
worked at full capacity to analyze 2,000 samples, but this year
they hope to analyze up to 10,000.
The team
will also explore the potential of NIR to measure iron and zinc.
Unfortunately, there is not enough natural variability in iron
content in maize to breed iron-rich lines, and to an extent the
same is true for zinc. However, iron deficiency is an extremely
important global problem: it is estimated that four to five
billion people are iron deficient. The team will therefore focus
on increasing the bioavailability of iron in maize—i.e. the
amount that can be absorbed by human consumers, rather than the
absolute amount.
The ultimate goal is to provide maize that farmers will want to
grow, that those on maize dependent diets will want to eat and
that the impact of micronutrient deficiencies in their diets
will be reduced.
“We’re
breaking new ground working on the bioavailability of
nutrients,” says Pixley. “This is exciting science.”
For more information, Kevin
Pixley, Associate Director, Global Maize Program (k.pixley@cgiar.org) |
