Rice is the primary food for more than three billion people around the world. Approximately one-fourth of the global rice crop is grown in low lying fields prone to seasonal floods. Rice is the only cereal crop that can withstand submergence; however, most rice varieties will die if fully submerged more than four days, costing producers an estimated $1 billion in annual crop losses.



Conventional breeding techniques have not produced a commercially viable submergence-tolerant rice variety. An international team of researchers from the International Rice Research Institute in the Philippines and at the University of California's Davis and Riverside campuses identified a gene that enables rice to survive complete submergence. The discovery allows for development of a new rice variety that can withstand flooding. Results of this study appear in the Aug. 10 issue of the journal Nature.



Using genetic mapping techniques, the research team identified a cluster of three genes that dictate whether rice plants are vulnerable or resistant to water submergence. The researchers focused on the Sub1A gene because this gene imparts a submergence tolerance to plants. The Sub1A gene affects the way the plants respond to hormones, such as ethylene and giberellic acid that are key to the plant's ability to survive even when inundated with water.



Going one step further, the researchers introduced the Sub1A gene into a rice variety that is especially suited for growing conditions in India. The resulting rice plants were not only tolerant of being submerged in water, but also produced high yields and retained other beneficial crop qualities. Development of submergence-tolerant varieties for commercial production in Laos, Bangladesh and India is now well underway.



Cultivation of the new variety is expected to increase food security for 70 million of the world's poorest people in developing countries. The researchers are also hoping the new gene will be useful in suppressing weeds and reducing herbicide applications for conventional and organic rice farmers in developed countries. The research team is now trying to identify all the genes that are regulated by Sub1A and to use this information to further improve tolerance to flooding and other stresses.



This project was funded in part by the USDA's Cooperative State Research, Education and Extension Service's National Research Initiative Plant Genome and Agricultural Plants and Environmental Adaptation programs. The NRI is the largest peer reviewed, competitive grants program in CSREES. It supports research, education and extension grants that address key problems of national, regional and multi-state importance in sustaining all components of agriculture. Additional funding was contributed by U.S. Aid for International Development and the German Federal Ministry for Economic Cooperation and Development.



CSREES advances knowledge for agriculture, the environment, human health and well-being and communities by supporting research, education and extension programs in the Land-Grant University System and other partner organizations.



SOURCE: USDA news release.