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Submergence-tolerant rice line now in the pipeline

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The Philippines
January 25, 2008

By Hanah Hazel Mavi M. Biag, PhilRice

“Teach rice how to swim and it will survive the floods,” rice experts say, which is the same idea behind the development of IR64 Sub1, a submergence-tolerant rice line.

Rice can withstand flooding, but not for long. The pursuit for a more resilient plant has paved the way for the discovery of a “submergence gene” that enables rice to survive complete submersion.

Usually, rice thrives in standing water, but complete submergence for more than a few days can be highly damaging resulting in yield losses, says Dr. Norvie L. Manigbas, a research fellow from PhilRice.

Containing the submergence tolerance (sub 1) gene IRRI line IR40931 came out after IRRI and the University of California-Davis discovered the gene in an Indian variety FR13A. The gene was then introduced to IR64, the most popular rice variety in the Philippines—hence, IR64 Sub1.

Dr. Manigbas said IR64 Sub1 is a non-genetically engineered rice plant that can survive, grow, and develop even after 10 days of complete submergence to murky and cloudy water.

The new rice line is not totally different from the original IR64 variety in terms of morphological characteristics as plant height, tillering, and yield performance.

As explained by Dr. Nenita Desamero of the PhilRice Plant Breeding and Biotechnology Division, with or without the submergence gene and planted under favorable condition, IR64 will have the same yield performance. However, when both are submerged under water for 7 to 10 days, IR64 Sub1 will survive and recover.

Normally, rice (without the sub1 gene) at tillering stage can survive for one week under submergence condition while seedlings can only last for three to five days.

As part of an IRRI’s project on the dissemination of its submergence tolerant rice variety, PhilRice now leads the national on-farm testing of IR64 Sub1 starting this year until 2009 with Dr. Desamero as the team leader and Dr. Manigbas as the lead scientist. The target sites are rainfed and/or irrigated areas prone to flash flooding for one to two weeks.

In July, pilot-testing in Bgy. Papaya, San Antonio, Nueva Ecija failed as the crop was not submerged during the evaluation period. Nonetheless, IR64, with and without sub1 gene, performed comparably with wet season yield of 4.5 tons per hectare. Under muddy irrigation water, crops recovered up to five to eight days of submergence, on-station results showed. The second on-station testing started in October 2007 while on-farm experiments began this January still in Bgy. Papaya.

“On-farm tests may provide hope for farmers who took the risk of planting rice during the rainy months, and whose fields are submergence-prone during the wet season,” Dr. Manigbas said.

 

 

 

 

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