Bangalore, Aug 10
Report of a new rice
cultivated by China is sure to be a welcome news for those worried about
global warming and climate change.
Flooded rice fields are a
known source of atmospheric methane -- the second most important
greenhouse gas after carbon dioxide -- and is said to be responsible for
about 20 percent of global warming.
While increasing rice
production has always been the primary objective of agricultural
researchers, not much attention was paid to reducing methane emission
from paddy cultivation. Existing efforts to mitigate rice-associated
methane emissions have focussed mainly on agricultural practices - such
as water management, fertilizer use, tillage and crop selection - which
are labour intensive.
Now a report in the journal Nature says
that Chinese scientists, in a ground-breaking demonstration, have grown a
new variety of rice called SUSIBA2 that meets the twin goals: it is
high yielding and, at the same time, the fields growing this rice emit
less methane than conventional varieties.
The new rice variety is
the result of collaborative work of scientists from the Fujian Academy
of Agricultural Sciences and Hunan Agricultural University in China with
researchers in the Swedish University of Agricultural Sciences,
Uppsala, and the Pacific Northwest National Laboratory in Washington.
The
authors generated SUSIBA2 by transferring genes from barley that are
responsible for the production of starch in stems and grains using what
is called "transcription factor technology".
In rice, the leaves
and stems take up carbon-dioxide (CO2), which is transformed through
photosynthesis into sugars. These sugars are used to produce plant
biomass or storage compounds, such as starch, in the shoots, roots and
rice grains.
The transgenic SUSIBA2 rice produces grains with a
high starch content by diverting more carbon (from photosynthesis) into
grains and stems, and less into roots. This results in less carbon being
available for methane-producing microbes present in the soil and hence
less emission of methane from rice fields.
The researchers
present evidence for this from field trials conducted in three regions
of China in three consecutive growing seasons.
They report "a
significant" reduction in methane emitted from SUSIBA2 rice plants,
compared with a widely grown unmodified variety.
"We suggest that
the use of SUSIBA2 rice in cutting methane emissions from paddies may
become more relevant with global warming," their study concluded.
The
dual benefit of 'high-starch, low-methane' rice variety indeed
"represents a tremendous opportunity for more-sustainable rice
cultivation, but it raises many issues," the journal said in an
accompanying article.
Besides the general questions surrounding
the use of genetically modified crops for human consumption, "we do not
yet have a clear picture of how this modification affects rice plants'
survival and general function," it said.
More important, it said,
"will be assessment of the long-term consequences of reduction of
root-exuded carbon on beneficial soil microbes".
Is the Chinese development something to be followed up by India?
"It
is quite interesting and challenging," Tikam Jain, a former assistant
director general of the Indian Council of Agricultural Research and
currently a consultant to the World Bank aided projects in Asia, said in
an email.
He says authorities must however first examine "if the
rice quality and its production capacities are acceptable to the Indian
farmers before any further action is taken by India for adopting this
technology".
(K.S. Jayaraman can be contacted at [email protected])
