Researchers have identified the key gene that determines the glycemic
index of rice, a breakthrough that offers breeders the opportunity to develop
rice varieties with different GI levels.
Research analyzing 235 types of
rice from around the world has identified the key gene that determines the
glycemic index (GI) of rice, a breakthrough that offers rice breeders the
opportunity to develop varieties with different GI levels to meet consumer
needs.
The research team from the
International Rice Research Institute (IRRI) and CSIRO’s Food Futures Flagship
narrowed down the candidates to one – Waxy was found to be the
main gene associated with GI in this study.
They then carried out the first
large-scale phenotyping of this Waxy trait and discovered a large variability
in GI in the rice varieties, ranging from a low of 48 to a high of 92, with an
average of 64.
Low GI foods are those measured
55 and less, medium GI are those measured between 56 and 69, while high GI
measures 70 and above.
When food is measured to have a
high GI, it means it is easily digested and absorbed by the body, which often
results in fluctuations in blood sugar levels that can increase chances of
getting diabetes, making the management of Type 2 diabetes difficult.
Conversely, foods with low GI are
those that have slow digestion and absorption rates in the body, causing a
gradual and sustained release of sugar into the blood, which has been proven
beneficial to health, including reducing the chances of developing diabetes.
Dr. Melissa Fitzgerald who led
the IRRI team said GI is a measure of the relative ability of carbohydrates in
foods to raise blood sugar levels after eating. Rice varieties like India’s
most widely grown rice variety, Swarna, have a low GI and varieties like Doongara
and Basmati from Australia have a medium GI, she said.
By applying the same method used
here, breeders may now be able to rapidly identify and quantify the impact of
low GI rices on blood sugar status, and develop breeding programs to select for
GI based on amylose content.
Future development of low GI rice
would also enable food manufactures to develop new, low GI food products based
on rice.
“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,” said Dr. Tony Bird, a CSIRO Food Futures Flagship researcher.
The article can be found
at: Fitzgerald MA et al. (2012)
Identification of a Major Genetic Determinant of Glycaemic Index in Rice.
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