Maclean et al. - 2002 - Rice almanac source book for the most important e

International Rice Information System
The International Rice Information System
(IRIS) is a database for managing and integrating
information on genetic resources,
phenotypic and molecular characterization,
crop improvement, and crop management.
Although major international initiatives for
germplasm collection and conservation
followed the Green Revolution, much
collected material is still not used because
information about it is difficult to access
and is not integrated with other data
sources. As a result, its potential impact on
agriculture has not yet been realized. The
sheer volume of unmanaged genealogical
information produced by plant scientists
precluded its wide use until now.
IRIS is the implementation for rice of the
International Crop Information System
(ICIS), which is being developed by
scientists of several CGIAR centers,
national agricultural research and extension
systems, and research institutes to
address this constraint for different crops.
The core of ICIS is a genealogy
management system that facilitates the
unique identification of germplasm and
manages synonyms and homonyms. It
allows users to trace cultivars back to their
ancestral landraces or to lines of unknown
pedigree; genealogies are automatically
updated as additional information on
ancestors is discovered. This information
can be accessed not only as text but also
as family trees—genealogical dendrograms.
The genealogy management system links to
a data management system, which integrates
data from different scientific
disciplines and will provide new insights
into crop adaptation. Geographical
information about germplasm evaluation
sites is associated with latitude and
longitude and can be analyzed with
geographic information systems.
For more information on IRIS, see www.iris.irri.org.
photosynthesis may be the only way to
guarantee feeding the growing population of
Asia over the next 50 years.
Hybrid rice
Hybrid vigor or heterosis is a universal phenomenon
that occurs in all biological systems. In
plant breeding, hybrid vigor denotes the
expression of more vigor than in the better parent
and the existing commercial variety.
Commercial exploitation of heterosis to
increase rice yields has been successfully
demonstrated in China, where nearly 18 million
ha of a total of 33 million ha of harvested rice
land were planted to F 1
hybrids by 1992. Rice
hybrids yield about 20% higher than do inbred
rice varieties.
Research in other countries also indicates
that heterosis in rice can increase yields by 15–
20% over those of the best available semidwarf
inbreds under irrigated conditions. Commercial
hybrids have been identified and/or developed
and grown on several hundred thousand hectares
in Vietnam, India, and the Philippines. Several
other countries are still searching for suitable
hybrids for commercial cultivation.
Cytoplasmic male sterility is the most
effective genetic tool for developing hybrid rice.
Photoperiod-sensitive and thermosensitive male
sterility systems have shown promise and have
resulted in some two-line commercial rice
hybrids in China. IRRI and some national
institutions are still developing these male
sterility systems. The use of chemically induced
male sterility has not been efficient enough for
deployment on a large scale.
Well-developed hybrid seed production
practices give average yields of 2 t/ha of seed.
Seed yields of 1–2 t/ha have been obtained by
commercial seed growers in India, Vietnam, and
the Philippines.
Tropical hybrid rice
The search for better tropical hybrids has
continued at IRRI for the past 20 years. The 15
commercially usable, male-sterile parental lines
bred to date have been designed for irrigated cultivation.
Experimental hybrids for rainfed
lowland systems have now been produced and
are being tested in India, the Philippines, and
Thailand. At the same time, new farm
management packages for the hybrids are being
developed. Private industry is showing
considerable interest in tropical hybrids to
become the provider of seed for each crop.
Farmers are wary of using hybrids: having to buy
seed for each crop means that their costs increase
by about $50 per hectare. But the increased
yields mean extra income of $135 to $200 per
hectare per crop.
International issues 35