International Rice Research Institute

Rice gene digs deep to triple yields in drought.

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A gene that gives rice plants deeper roots can triple yields during droughts, according to Japanese researchers writing in Nature Geneticsthis 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 environmentalstresses,” 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.”

Source: Scivx

Rice gene holds clue to diabetes risk.

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Contrary to popular belief, a new study suggests that eating rice does not substantially raise blood sugar levels – thus increasing the risk of type 2 diabetes – although researchers warn that some varieties of rice may need to be avoided.

The study was published this month in the journal Rice by the International Rice Research Institute (IRRI) in the Philippines, and Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO).

It found that as many as three quarters of 235 rice varieties analysed had a low to medium glycaemic index (GI), and were therefore less likely to lead to diabetes.

GI measures the effect of carbohydrates on blood sugar levels. Low GI foods are more slowly absorbed, causing a gradual release of sugar in the body and a lower risk of diabetes. Doctors often advise diabetics to avoid rice, believing it is a high-GI food.

The findings could have important implications for Asia where rice is the staple food for 3.5 billion people, and diabetes is a growing public health concern, said Melissa Fitzgerald, who led the IRRI team.

“With or without diabetes, it will be difficult for them to give up rice,” Fitzgerald told SciDev.Net.

The International Diabetes Federation estimates that by 2030, seven of the ten countries with the highest number of diabetics will be in Asia, straining public health budgets.

The researchers found that the so-called “waxy gene”, and the related amylose content, are the key determinants of the GI of rice. Rice varieties with high amylose have lower GI.

Amylose is also the chemical component which makes rice either firm or sticky after cooking, influencing consumer preferences. The waxy or sticky rice types have the highest GI, but some sticky rice varieties have little or no amylose.

Rice varieties with a low to medium GI include Basmati, India’s widely grown Swarna variety, and Doongara from Australia.

The researchers say that the findings will help rice breeders to develop lower GI rice by identifying varieties with better traits.

Tony Bird, a CSIRO Food Futures Flagship researcher said “this is good news for diabetics and people at risk of diabetes who are trying to control their condition through diet, as it means they can select the right rice to help maintain a healthy, low-GI diet.”

But Claire Kerslake, a health counsellor and certified diabetes educator in Australia, warned that although it was true that some varieties of rice are lower in GI, “the GI is only part of the picture. You also need to take into account the total carbohydrate load”.

She advised diabetics to limit carbohydrates such as rice “to half a cup per meal.”

Source: ScivX