Researchers Aim to Flick The High-Carbon Switch on Rice
Posted by Unknown in Genetics, Research and Studies, Rice on Monday 28 January 2013
'C4 photosynthesis', as used by maize and sorghum, could greatly boost rice yields, after a decade of slowing improvements.
Codename: C4
rice project. Mission: to modify photosynthesis in rice to boost crop
yields. Duration: 15 to 25 years. This might sound like science fiction,
but it is already under way at the International Rice Research
Institute (IRRI) in
the Philippines, where William Paul Quick and his team have been working
since 2008 on changing the photosynthesis process in rice from the C3
carbon-fixation mechanism, common to 98% of all plants, to its much more
efficient C4 counterpart.
Some 50
species, including maize and sorghum, have completed this step
naturally, enabling the plants to devote most of their energy to
carbon-fixing, and thus to growth. "At present we are studying how far
the cell structures and enzymes required to achieve C4-type
photosynthesis are already present in rice and closely related plants,"
says Nourollah Ahmadi, a rice specialist at France's Centre for International Co-operation on Farming Research for Development. "The
aim is to activate the available but as yet inactive cell structures
and enzymes and to introduce the ones that are lacking by genetic
transformation, drawing on other plants."
This could
increase output by as much as 50%, bringing about another green
revolution, capable of responding to the foreseeable demand for food in
2050, when there will be 9 billion mouths to feed. Rice is currently the
staple foodstuff for more half the world's population, with more than 1
billion people depending on rice farming for their livelihoods. "For
every additional billion people, an extra 100m tonnes of rice will need
to be produced," says Ahmadi. In contrast, the annual increase in yields
has slowed since the 1990s, from 2% to just 1%.
Research into
rice now concentrates on creating varieties that are more productive and
more resistant to the various forms of stress, caused by disease (such
as pyriculiariosis) or environmental factors (flooding, drought, extreme
temperatures and high salt concentrations).
"Rice will be
one of the cereals most affected by climate change," says Robert
Zeigler, the head of IRRI. "So it's vital to prepare production systems
and rice growers for change if we want to maintain a certain dynamic."
Hopes are consequently high for the programme launched by IRRI and China
to sequence the genome of 10,000 of the 120,000 known rice varieties.
The first results are due in June.
"Thanks to new
sequencing techniques, we can determine the specific features of the
genome of any particular variety," says Mathieu Lorieux, a geneticist at
France's Development Research Institute (IRD). "Our work then consists
in cross-breeding the most useful species to obtain new ones that meet
consumer demands and environmental constraints, and are resistant to
disease."
Lorieux is
taking part in a programme to overcome the sterility barrier between
Asian (Oryza sativa) and African rice (Oryza glaberrima), the idea being
to develop hybrid varieties combining the former's productivity with
the robustness of the latter. He is also working on the plant's
architecture, so that each shoot produces more grain.
In 2011 IRRI launched a four-year programme on the Mekong delta, in Vietnam, to add flood and salt-tolerant genes to rice.
"More or less
all over the world, the potential yield from rice is about 10 tonnes a
hectare, whereas the global average is only 4.5 tonnes," Ahmadi
explains. "But the effort required to bridge this gap is increasing all
the time."
No transgenic
rice varieties are currently being cultivated, but "golden rice", a
variety developed a decade ago to have added vitamin-A, did cause
controversy. Lorieux is certain we shall one day eat transgenic rice:
"If a new disease appears and there are no resistant rice varieties, we
shall have to look for a resistant gene elsewhere or maybe make a
synthetic gene ... or give up growing rice."
This article originally appeared in Le MondeGilles van KoteGuardian Weekly
