New rice variety thrives on saline water

LOS BAÑOS, LAGUNA—After the scuba rice which was designed to survive water submergence, the International Rice Research Institute (IRRI) has announced the development of another rice variety that can tolerate saline waters.

The IR63307-4B-4-3 rice variety contains the Saltol gene that is responsible for the salinity tolerance trait of the plant, according to IRRI scientist Dr. Rakesh Kumar Singh.

The variety can survive for about 20 days in coastal rice-growing lands affected by salinity from seawater.

Singh said that in 1997, Filipino researcher Glenn Gregorio first identified the chromosome region, called chromosome 1, in Pokkali rice from India, where Saltol is located.

This was supplemented by the findings of a few more researchers over the years until they were able to narrow down the chromosome region to 1.2 centimorgans (distance along a chromosome).

“In a year or so, scientists will be able to fully single out Saltol from the chromosome region,” Singh added.

The introgression of Saltol to rice varieties is done through the marker-assisted selection, a tool that relies on DNA markers in determining a particular trait.

In Bangladesh, the BRR1 dhan 47 plus Saltol was released to farmers in 2007. It was the same variety as the IR63307-4B-4-3 in the Philippines.

Singh said they are coming up with more salt-tolerant varieties.

Plants in coastal areas take in salt through the water absorbed from the soil.

Salt uptake is even greater under hot weather conditions, as plants tend to suck up more water.

The Saltol provides a “restriction mechanism” at the root level of the plants to block up to 99 percent of salt, Singh explained.

“But the salt, once inside cannot come out,” he said.

In these cases, the Saltol allows vecules inside the plant cell to act like “thrash cans” or depository of up to 100 millimolars (concentration in a liquid) of the salt.

This mechanism is called the “cell level partitioning,” he said, which is absent in a nonsalt-tolerant variety.

Regular rice variety in coastal areas immediately expires within a week due to salinity, while the IR63307-4B-4-3 can last up to 20 days under the same conditions.

The Philippines has about 400,000 hectares of coastal rice-growing land affected by salinity from seawater.

“Farmers don’t often plant in this region because of the risk of crop failure,” Singh said.

He said that under high salt stress, Philippine rice varieties typically produce less than a ton of rice per hectare.

With Saltol on the IR63307-4B-4-3, the rice variety can yield 6.5 to 7 tons per hectare.

The salt-tolerant rice promises a total potential of increased rice production of 0.8 to 1.0 million tons per annum to Filipino farmers.

In a statement, IRRI said the new variety was recommended for approval for release in the Philippines in late April.

The Philippine Rice Research Institute has started distributing small amounts of the seeds to farmers for further adaptation tests.

Copyright 2009 INQUIRER.net and content partners. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.