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[CEBU, PHILIPPINES] 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.
Link to full paper in PLoS ONE