by Katherine
Nightingale, SciDev.Net
Scientists
have for the first time genetically modified
white corn to increase the levels of several
different vitamins — bringing closer the
prospect of crops that can deliver full
nutritional requirements.
The team increased the levels of
beta-carotene, the precursor of vitamin A
170-fold; levels of vitamin C six-fold and
also doubled the folic acid in the African
staple.
White corn normally contains only trace
amounts of beta-carotene. Diseases caused by
low consumption of vitamin A, vitamin C and
folate are widespread in Africa, says lead
researcher Paul Christou of the University
of Lleida in Spain.
Until recently researchers had struggled to
introduce multiple genes into a plant
simultaneously to create several different
traits, he told SciDev.Net.
His team developed a method that transfers
the desired genes into plant embryos by
bombarding them with gene-coated metal
particles. The resulting plants are then
screened for those containing the required
genes.
The method can introduce an unlimited number
of transgenes into any plant, says Christou.
The method is quicker than others and the
genes persist in subsequent generations.
Most researchers do it "the hard way" by
putting individual genes into plants and
then crossing and breeding them sexually.
Those containing two different traits are
crossed again and so on. "It would take
years … we can do it in one shot," he says.
The team is now trying to introduce genes
for other vitamins into the corn along with
microelements such as calcium, iron,
selenium, and zinc, and genes for resistance
to insects and the parasitic plant striga.
The researchers are also introducing genes
into varieties of rice.
They aim to have prototype plants containing
25–30 transgenes in five years, but getting
them past GM regulatory processes and into
the field will be the difficult part, say
Christou.
After field trials in the United States next
year, the team will use conventional
breeding to cross the tri-vitamin crops with
local varieties.
The research shows the value of
biotechnology for simultaneously improving
multiple nutritional traits, says Ed Cahoon
of the US-based University of Nebraska and
part of the BioCassava Plus project, an
initiative to engineer cassava into a
complete meal. The project has so far
introduced genes for increased nutrient
content, virus resistance and decreased
cyanide content individually into cassava
and field trials will be carried out in
Nigeria (see
'Super cassava' to enter field trials).
He says the method of "stacking" genes has
been used commercially before — to confer
resistance to herbicides and insects in
maize, for example — and that this research
extends the technology to have direct value
to consumers.
The research was published last month in the
Proceedings of the National Academy of
Sciences (27 April).
Link to abstract in the Proceedings of
the National Academy of Sciences*
*Free access for readers in developing
countries
