A new flood-resistant rice variety developed at the International Rice Research Institute (IRRI) in the Philippines is proving to be popular in the flood-prone areas of India and Bangladesh.
In India, since release in August 2009, more than 100,000 farmers have received seeds of the ‘Swarna-sub1’ variety and it is now being grown over 12 million hectares, the IRRI said in a press note this month (14 September). Rice covers 44 million hectares in India.
IRRI scientists helped modify the popular Indian rice Swarna by introducing a gene sub1 (for submergence) that helps it survive in flood waters. They are now working with India’s agriculture ministry to introduce it in all flood-prone areas and improve the country’s food security.
‘’The new Swarna-sub1 is 99 per cent similar to Swarna genomically (genetically). It can tolerate complete submergence for 14 to 17 days whereas Swarna cannot withstand submergence for more than four to five days,’’ IRRI scientist Umesh Shankar Singh told SciDev.Net.
The scientists used a crop improvement technique called ‘marker assisted selection’ in which a marker — usually a physical or chemical trait in a plant — is used to help locate and isolate a gene of interest, such as a gene for higher yield, stress tolerance or pest resistance.
‘’Swarna was the first rice variety where IRRI transferred the sub 1 gene using marker-assisted selection (MAS) breeding,’’ Singh said. 'We are hoping that Swarna-sub1 would entirely replace Swarna and spread to other flood-prone areas all over the country.’’
While it takes six to eight generations for a desired trait to prove stable, MAS breeding cuts short the process to three to four generations by allowing the breeder to observe a marker or unique genetic sequence linked to the trait.
‘’In India almost 12 million hectares of rainfed lowland rice area is flood prone and out of this about six million hectares are submerged almost every year,’’ said Singh. ‘’IRRI is planning to put the sub 1 gene in all rice varieties as they may face flooding in one or other area particularly when cultivated during the wet season.’’
Indian scientists are also testing other flood-tolerant varieties in states where farmers do not prefer the original Swarna variety. “Swarna is not a popular variety in Tamil Nadu,” Thangamuthu Jeyaraj, director of the Tamil Nadu Rice Research Institute in Aduthurai, said.