Two breakthroughs in rice science: flood-tolerance and drought-tolerance boost yields

Rice, the world's most important staple crop, recently was the subject of a tremendous speculative boom-and-bust cycle, with prices going through the roof a few months ago, and collapsing today. This volatility leaves both small farmers and entire states vulnerable. However, two scientific breakthroughs in rice crop science may give producers and consumers alike a new weapon against this volatility. They may also go a far way in solving hunger.

In a first development, scientists from the International Rice Research Institute (IRRI) report that they have found a way to "waterproof" versions of popular varieties of rice, which can withstand 2 weeks of complete submergence. This can double crop output and can save millions of tonnes of rice from losses, which is enough to feed tens of millions of people. In another exciting breakthrough, a PhD student at the University of Alberta found a way to make upland rice double its yield in dry areas, where the crop is grown by some of the world's poorest.

In short, two of the biggest problems - flood intolerance and drought intolerance - associated with the two most common rice growing techniques - paddy and upland - have been solved. Interestingly, the the water-proof crops are not genetically modified, but created by precision breeding.

Flood-tolerance
The waterproof rice crops have passed tests in farmers' fields with flying colors (see time-laps video for a short-cut). Several of these varieties are now close to official release by national and state seed certification agencies in Bangladesh and India, where farmers suffer major crop losses because of flooding of up to 4 million tons of rice per year. This is enough rice to feed 30 million people.

The flood-tolerant versions of the so-called "mega-varieties" — high-yielding varieties popular with both farmers and consumers that are grown over huge areas across Asia — are effectively identical to their susceptible counterparts, but recover after severe flooding to yield well.

A 1-9 November tour of research stations and farms in Bangladesh and India led by David Mackill, senior rice breeder at the International Rice Research Institute (IRRI), marked the successful completion of the project titled "From genes to farmers' fields: enhancing and stabilizing productivity of rice in submergence-prone environments", funded for the past 5 years by Germany's German Federal Ministry for Economic Cooperation and Development (BMZ).

The new varieties were made possible following the identification of a single gene that is responsible for most of the submergence tolerance. Thirteen years ago, Dr. Mackill, then at the University of California (UC) at Davis, and Kenong Xu, his graduate student, pinpointed the gene in a low-yielding traditional Indian rice variety known to withstand flooding. Xu subsequently worked as a postdoctoral fellow in the lab of Pamela Ronald, a UC Davis professor, and they isolated the specific gene—called Sub1A—and demonstrated that it confers tolerance to normally intolerant rice plants. Dr. Ronald's team showed that the gene is switched on when the plants are submerged:
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A geneticist from UC Riverside, Julia Bailey-Serres, is leading the work to determine exactly how Sub1A confers flood tolerance. "Sub1A effectively makes the plant dormant during submergence, allowing it to conserve energy until the floodwaters recede," said Dr. Bailey-Serres.

Typically, rice plants will extend the length of their leaves and stem in an attempt to escape submergence. The Sub1A gene is an evolutionarily new gene in rice found in only a small proportion of the rice varieties originating from eastern India and Sri Lanka. The activation of this gene under submergence counteracts the escape strategy.

"This project has been a great success, not only in its results but also in the truly international collaboration that made the project possible," said Dr. Mackill, referring to the several national organizations, including the Bangladesh Rice Research Institute, India's Central Rice Research Institute and Narendra Dev University of Agriculture and Technology.

The potential for impact is huge. In Bangladesh, for example, 20% of the rice land is flood prone and the country typically suffers several major floods each year. Submergence-tolerant varieties could make major inroads into Bangladesh's annual rice shortfall and substantially reduce its import needs. - Dr. Mackill

Using modern techniques that allow breeders to do much of their work in the lab rather than the field, Dr. Mackill and his team at IRRI were able to precisely transfer Sub1A into high-yielding varieties without affecting the characteristics—such as high yield, good grain quality, and pest and disease resistance—that made the varieties popular in the first place.

The impact is evident for farm families as well as at a national production level. To be part of this project as it has moved from a lab in California to rice fields in Asia has been inspiring and underscores the power of science to improve people's lives. - Dr. Ronald

Because plants developed through this "precision breeding," known as marker-assisted selection, are not genetically modified organisms (GMOs), the new Sub1 varieties are not subject to the regulatory testing that can delay release of GMOs for several years.

Once Sub1 varieties are officially released within the next 2 years, the key will be dissemination to smallholder farmers in flood-prone areas. IRRI is leading this initiative through a grant from the Bill & Melinda Gates Foundation and Japan's Ministry of Foreign Affairs.

Drought-tolerance
From too much water, to not enough of it: Jerome Bernier, a PhD student in the University of Alberta Department of Agricultural, Food and Nutritional Science, has found a group of genes in rice that enables a yield of up to 100 per cent more in severe drought conditions. Doubling the output of these upland rice crops is a major step forward for some of the world's poorest, who try to grow the crop in the most distressed areas.

The discovery marks the first time this group of genes in rice has been identified, and could potentially bring relief to farmers in countries like India and Thailand, where rice crops are regularly faced with drought. Rice is the number one crop consumed by humans annually.

The results of the study were published recently in the plant sciences journal Euphytica. Bernier's research began four years ago and focused on upland rice, which, unlike the majority of rice crops, grows in non-flooded, dry fields. "If drought hits, the yield can drop to almost nothing," Bernier said. He too conducted his research at the International Rice Research Institute in the Philippines, in conjunction with scientists there and in India.

He started with 126 genetic markers and narrowed his search to a group of genes that had the desired impact. In very severe drought conditions, rice strains with the new genes were shown to produce twice as those strains that did not have the genes. The new genes stimulate the rice plants to develop deeper roots, enabling it to access more of the water stored in the soil.

"For subsistence farmers who rely on the crop to feed their families, this extra yield can make a world of difference," said Bernier.

Less loss to drought may also mean an increased supply of rice globally, said Dean Spaner, Bernier's project supervisor and a professor of agricultural, food and nutritional science at the University of Alberta.

The young scientist's research was funded in part by the Canadian International Development Agency and the Consultative Group on International Agricultural Research.


The International Rice Research Institute (IRRI) is the world's leading rice research and training center. Based in the Philippines, with offices in 13 other countries, IRRI 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.

IRRI is one of 15 centers funded through the Consultative Group on International Agricultural Research (CGIAR), an association of public and private donor agencies.

Time-lapse video: courtesy of IRRI.

References:
Jérôme Bernier, et al. "Characterization of the effect of a QTL for drought resistance in rice, qtl12.1, over a range of environments in the Philippines and eastern India", Euphytica, Wednesday, October 01, 2008, DOI 10.1007/s10681-008-9826-y

International Rice Research Institute: Waterproof rice provides flood relief for poor farmers - dedicated video page.

International Rice Research Institute: Rice Library and Rice Knowledge Bank.