guardian.co.uk,
SciDev.Net, part of the Guardian Environment Network, Wednesday 27 July 2011
 |
| A farmer works at a rice planting field. Photograph: Guang Niu/Getty Images |
Inoculating
rice seeds with fungi makes the plants more tolerant of salt, drought and cold
— all of which may become more common as the climate changes, according to researchers.
The
researchers obtained two types of endophytic fungi, which have symbiotic
(mutually beneficial) relationships with plants. One was from coastal
dunegrass, and the other from a variety of wild strawberry that thrives in
geothermal soils even in below-freezing winter temperatures.
When seeds
of two commercial rice varieties were inoculated with the fungi, the resulting
plants, grown in greenhouses, had increased growth and grain production, and
were more tolerant of drought.
In
addition, plants inoculated with fungi from coastal plants thrived under saline
conditions, and those receiving fungi from wild strawberries grew well in low
temperatures, according to the research published this month (5 July) in PLoS
One.
"The
fungus pretty much does all the work," said Russell J. Rodriguez,
co-author of the research and a microbiologist with the US Geological Survey.
"Within 24 hours, we saw the benefits. [Inoculated] plants were growing up
to five times faster."
The
technique does not change the rice plant's genetic material — its DNA — he
said. "But the expression [switching on and off] of genes is modified and
the plant now has the ability to resist environmental stress," he told
SciDev.Net.
The
researchers do not understand the mechanism but suggest that the fungi could be
producing a substance that regulates plant growth.
In their
symbiotic relationship with the plants, the fungi confer stress tolerance in
exchange for nutrients, a phenomenon known as 'symbiogenics' because one
symbiotic partner influences the expression of the other's genes.
The
technique should work for different rice varieties and other crops, such as
corn and peas, said Rodriguez, adding that the researchers are now trying to
make rice plants heat tolerant, too.
Glenn
Gregorio, who studies stress-tolerant plants at the International Rice Research
Institute in the Philippines, said the experiment on salt tolerance was
"impressive and very promising".
But further
experiments are needed to see if the rice thrives under field conditions, he
said, because fungi usually require specific habitats, such as geothermal
soils, to survive.
"In
field conditions, the soil and the overall environment [are] 'contaminated'
with other organisms, which may also interact with the plant and, in essence,
compete with the fungi," Gregorio said.
Rodriguez
said his team has been collaborating with African and Korean scientists to test
the findings in the field.
