HOLD FOR RELEASE: THURSDAY, AUG. 21, 1997, 4 P.M. E.D.T.
Contact: Blaine P. Friedlander, Jr.
Office: (607) 255-3290
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Compuserve: 72650,565
http://www.news.cornell.edu
ITHACA, N.Y. -- With a burgeoning world population and fewer places to grow
food, Cornell University scientists have begun to locate high-production
genes from wild plants to put into domesticated, edible crop plants -- thus
boosting food production worldwide, according to their report in the
journal Science.
"We are fortunate to be living at a time when genetic modification holds
much promise for improving crop performance," said Susan R. McCouch,
Cornell assistant professor of plant breeding. "However, most of the
advances in molecular genetics have been directed toward traits other than
yield, largely because of the complexity of this trait." McCouch and Steven
D. Tanksley, Cornell's Liberty Hyde Bailey Professor of Plant Breeding and
Biometry, have co-authored the article on how they have learned to increase
production of certain plants by using wild genes, "Seed Banks and Molecular
Maps: Unlocking Genetic Potential from the Wild," in Science, (Aug. 22,
1997).
While examining wild rice and tomatoes, McCouch, Tanksley and their
colleagues have systematically used molecular markers to map genes of rice
and tomato plant varieties and looked for specific loci or genes -- known
as the Quantitative Trait Locus, or QTL -- that would tend to boost
production. Before the availability of molecular markers, breeders had no
way of finding the genes from the wild species because there was no way to
identify the functions of genes controlling complex (or quantitative)
traits in any species.
The researchers have genetically mapped rice and made the information
available through the rice genes database over the World Wide Web
data to boost rice production in their area of the globe. Although the
wild species generally are considered useless for yield improvement --
since they do not produce much rice, have small grains and the plant tends
to shatter -- there is "some useful genetic treasure."
The researchers started with domesticated rice, Oryza sativa. By combining
genes from the wild variety with genes from domesticated rice, the
researchers observed between a 15 percent and 17 percent improvement in
grain yield. Using QTL analysis, they deduced that the yield improvement
was the result of two production-boosting QTLs: simply named YLD1 and
YLD2, coming from the wild rice, O. rufipogon.
Results from harvesting wild tomato QTLs were also dramatic. In extensive
testing, tomato QTLs from the wild species Lycopersicon hirsutum
outperformed the elite tomato variety by 48 percent for yield, 22 percent
for soluble contents and 33 percent for fruit color. Tanksley said this
research has been confirmed around the world under a variety of conditions,
and fruit size has been increased in tomato lines by introduction of genes,
identified through genetic mapping, from the tomato ancestor L.
pimpinellifolium.
In tomato and rice plant varieties, the researchers sampled a variety of
wild species available in seed repositories and found a high proportion --
almost a 50 percent increase -- of useful QTL alleles (mutated genes) that
could boost plant production. "This underscores the point that exotic
germplasm often contains genes that are capable of improving traits,"
Tanksley said.
Wild plant species of rice, considered one of the world's top staple crops,
were domesticated about 10,000 years ago, during humanity's transition from
nomadic hunter-gatherers to agrarians. "Considering that flowering plants
[like rice and tomatoes] first evolved over 150 million years ago, crop
plants as we know them have existed for the mere blink of an evolutionary
eye," Tanksley said.
Modern plant breeding -- agricultural practices for the past 100 years --
might be a victim of its own success. While plant breeding techniques have
been successful in developing high-yielding rice and tomato species, the
process itself threatens the genetic base. New plant varieties are usually
derived from crosses between close relatives, the researchers explained,
and this results in a "genetic bottleneck" that can result in losing plant
production and making plants more vulnerable to pests and disease.
Said McCouch: "Owing to the advent of molecular mapping and our ability to
scan the genomes of wild species for new and useful genes, we may be now in
a position to unlock the genetic potential of those germplasm resources."
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