Rice Farming


California Flood-Tolerant Rice
To Debut In Asia

By Brenda Carol

It’s a long way from the drought-stricken California farmscape to Delhi, India, but researchers in the Golden State have been instrumental in developing rice varieties that can withstand – even thrive – under waterlogged conditions. The lack of water in California is often problematic, and the over abundance of water in “hurricane alley” states, such as Louisiana, is equally problematic.

However, it’s an entirely different scenario on the other side of the world. Asian rice-producing regions commonly flood at the beginning of the season, which can be devastating to rice emergence and subsequent yield and quality. Farmers sometimes suffer crop losses totaling up to four million tons of rice per year.

Research into submergence-tolerant varieties is now offering a ray of sunshine, or at least adaptability, in flood-prone regions. Geneticists have identified a gene that enables a rice plant to shut down under adverse flooding conditions, yet re-emerge vigorously when conditions improve. Julia Bailey-Serres, Professor, UC Riverside Department of Botany and Plant Sciences, is a member of a research team that is breeding flood-tolerance characteristics into rice varieties.

The gene, dubbed “Sub1A,” has already been successfully bred into several varieties and will likely be released commercially by national and state seed certification agencies in Bangladesh and India in 2009. Research conducted to date has shown that varieties with the Sub1A gene enable a rice plant to withstand up to two weeks of complete submergence and still recover to yield comparably to a rice plant under more favorable climatic conditions.

How the Sub1A gene works
“Sub1A effectively makes the plant dormant during submergence, allowing it to conserve energy until the floodwaters recede,” Bailey-Serres says.

Work on the flood-tolerant gene has been a collaborative effort that has been ongoing for many years. David Mackill, currently senior rice breeder at the International Rice Institute in Bangladesh, started working on the project while he was at UC Davis 13 years ago. Along with Kenong Xu, a graduate student, he pinpointed the gene in a low-yielding traditional Indian rice variety known to withstand flooding. The gene is found in only a small proportion of rice varieties originating from eastern India and Sri Lanka.

Typically, rice plants that are submergence-intolerant accelerate leaf elongation under water and exhaust carbohydrate reserves. The Sub1A gene counteracts leaf elongation and carbohydrate consumption by rendering the plant temporarily dormant. The dampening of ethylene production and gibberellin responsiveness in Sub1A rice allows plants to maintain the capacity for re-growth when environmental conditions once again favor rice plant growth.

Relevance to U.S. rice flooded by hurricanes
As mentioned earlier, flooding can be problematic in “hurricane alley” states, such as Louisiana, which begs the question of whether Sub1A varieties would have a fit in this scenario.

“Not really,” says Steve Linscombe, veteran rice breeder with the LSU AgCenter. “The hurricane season doesn’t begin until June, and most of our hurricanes occur in August and September. Although a lot of our rice may be flooded by hurricanes, the crop typically isn’t submerged for weeks.

“In addition, remember that the Sub1A gene works on rice that is flooded before mid-season. Our problems with flooding usually happen on the back end of the season. It really wouldn’t offer any benefit to maturing and mature rice because it doesn’t prevent the rice from sprouting, which sometimes happens to our rice crop if it is covered with water from a hurricane.”

However, Linscombe does note that the Sub1A varieties he has observed at the International Rice Research Institute (IRRI) are impressive under the circumstances for which they were bred.

“Where early season flooding is a serious issue, these varieties will offer a substantial improvement,” he says.

Collaborative effort touted for project’s success
Several national organizations have worked collaboratively to bring flood-tolerant varieties to the marketplace. They include the Bangladesh Rice Research Institute, India’s Central Rice Research Institute and Narendra Dev University of Agriculture and Technology. IRRI has been leading the initiative through a grant from the Bill & Melinda Gates Foundation and Japan’s Ministry of Foreign Affairs. Based in the Philippines, with offices in 13 other countries, IRRI (www.cgiar.org) is an autonomous, nonprofit institution focused on improving the well-being of present and future generations of rice farmers and consumers, particularly those with low incomes, while preserving natural resources.

“The impact is evident for farm families and at a national production level,” says UC Davis assistant plant pathologist Pamela Ronald, an integral part of the team. “To be part of this project as it has moved from a California lab to rice fields in Asia has been inspiring and underscores the power of science to improve people’s lives.”

Because flood-tolerant varieties have been developed through marker-assisted selection rather than genetically modified organisms (GMOs), the new Sub1 varieties are not subject to the regulatory testing that can delay the release of GMO varieties.

“This project has been a great success, not only in results but also in the international collaboration that made the project possible,” Mackill says.

Brenda Carol is a freelance writer based in California. Contact her at (805) 226-9896 or brenda@brendacarol.net.

UC Davis scientists receive prestigious Discovery Award

The U.S. Department of Agriculture has given one of its highest research awards to UC Davis rice geneticist Pamela Ronald and two other scientists in recognition of their work developing new rice varieties that can withstand flooding.

The Discovery Award, which recognizes outstanding researchers who address key agricultural problems of national, regional and multistate importance, was presented Dec. 5 at UC Riverside by Gale A. Buchannan, the USDA’s undersecretary for research, education and economics. The award was given to Ronald; UC Riverside genetics professor Julia Bailey-Serres; and David J. Mackill, a researcher formerly of UC Davis and now at the International Rice Research Institute in the Philippines.

“Each of the groups brought distinct expertise to the project,” Ronald said. “Dave Mackill led the breeding work and Julia Bailey-Serres, who joined the project in 2002, is leading the work to understand how regulation of the ERF genes control the plant’s complex response to submergence stress.”