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  • Rice gene digs deep to triple yields in drought

IRRI

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  • Severe drought can cause as much as 40 per cent yield loss

  • The gene causes the roots to grow further down towards water and nutrients

  • This produces grains during drought, raising hopes for better rice crops

A gene that gives rice plants deeper roots can triple yields during droughts, according to Japanese researchers writing in Nature Genetics this week (4 August).

Rice is a staple food for nearly half of the world's population, but is also particularly susceptible to drought owing to its shallow roots, researchers say.

“If rice adapts to or avoids drought conditions using deeper roots, it can get water and nutrients from the deep soil layers.”

Yusaku Uga

The new study shows that by pointing roots down instead of sideways, the Deeper Rooting 1 (DRO1) gene results in roots that are nearly twice as deep as those of standard rice varieties.

"If rice adapts to or avoids drought conditions using deeper roots, it can get water and nutrients from the deep soil layers," says the study's lead author Yusaku Uga, a researcher with Japan's National Institute of Agrobiological Sciences.

Uga and his team found that in moderate drought conditions, the yield of rice with DRO1 was double that of the shallow-rooted rice variety. Under severe drought conditions, this increased to 3.6 times greater.

"The most important point is that we had rice grains produced under drought conditions," says Uga. "When rice crops just tolerate drought, they cannot get water and nutrients, resulting in a kind of survival mode."

The DRO1 gene occurs naturally in more than 60 rice varieties. For the study, the research team crossbred a rice variety carrying DRO1 with a shallow-rooted variety and then bred the offspring together to produce a rice crop in which DRO1 was uniformly present.

The International Rice Research Institute (IRRI) estimates that an additional 8-10 million tonnes of rice will be needed each year to keep rice prices affordable at around US$300 per tonne. Finding a drought-resistant variety of rice may be key to attaining this goal, according to researchers.

"Drought is the most widespread and damaging of all environmental stresses," says Sophie Clayton, head of communications at IRRI. "In some states in India, severe drought can cause as much as 40 per cent yield loss [in rice crops]. Moreover, with the onset of climate change, droughts may become more frequent and more severe."

Link to full study in Nature Genetics

References

Nature Genetics doi:10.1038/ng.2725 (2013)