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Grain development

New salt-tolerant rice strain could help in fight for food security

By RJ Whitehead , 16-Apr-2013

A newly developed strain of rice tolerant to levels of salt found in seawater might become available to farmers in the next four to five years, and its impact on food security could be massive.

Developed by a team at the International Rice Research Institute, the new rice has taken two decades to produce in laboratory conditions. Unlike regular food rice, the new line is able to expel the salt it takes from the soil into the air through salt glands on its leaves.

"This will make saline-stricken rice farms in coastal areas usable to farmers," said lead scientist Kshirod Jena of the IRRI. "These farmlands are usually abandoned by coastal farmers because the encroaching seawater has rendered the soil useless. That means livelihood lost for these communities." 

It also means the availability of new land to cultivate, not least in China, where rice production is slowing alarmingly.

Dysfunctional parents

The new rice was bred by successfully crossing two different rice parents: the exotic wild rice species Oryza coarctata and rice variety IR56 of the cultivated rice species O. sativa

O. coarctata is extremely difficult to cross with cultivated rice varieties because its location in the rice genome sequence is at the other end of the spectrum from other rice varieties such as IR56.

"When we cross two types of rice with genomes so far off from each other in the genome sequence, the resulting embryo tends to abort itself," said Jena. "We've been trying to backcross these types of interspecific hybrids since the mid-1990s, but we have never been successful, until now."

Scientists did not give up on crossing the two types of rice because O. coarctata is a special type of rice that grows in brackish, salty water, making it highly resistant to saltiness in the soil. 

According to Jena,it can tolerate a salinity concentration similar to that of seawater, whereas current salinity-tolerant rice varieties can only cope with half that concentration. However, O. coarctata is unsuitable for the production of edible rice.

Rescued embryos

The first sign of good news came when, out of 34,000 crosses made, three embryos were successfully “rescued.” Of these three, only one embryo germinated to produce one single plant.

"We treated this single plant survivor like a baby," said Jena.The surviving plant was then transferred into a liquid nutrient solution to ensure its survival. 

Once the plant was strong enough, it was grown in the field, where Jena and his team used it to backcross with IR56—a process to ensure the resulting progeny will contain all traits of IR56, and take only the salt tolerance O. coarctata trait.

Jena’s team is now working to perfect its new, doubly salt-tolerant rice to make sure it is suitable for farmers and consumers. The scientists hope to have the new variety available for farmers to grow within the next half-decade.

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