"Waterproof" versions of popular varieties of rice, which can withstand
2 weeks of complete submergence, have passed tests in farmers' fields
with flying colors. 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 "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 a
project, 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.

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," he said. "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."

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," said Dr. Ronald. "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."

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.

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
(www.cgiar.org).
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