Posted on 4-3-2003
Crop
Improvement: Dying Breed"
Nature 421, Pages 568 - 570 (2003), by Jonathan Knight
Public-sector research into classical crop breeding is withering,
supplanted by 'sexier' high-tech methods. But without breeders'
expertise,
molecular-genetic approaches might never bear fruit. Jonathan
Knight reports.
Normally, at this time of year, agricultural scientists from
around the
world would be converging on the headquarters of the International
Maize
and Wheat Improvement Center, known as CIMMYT, in Texcoco, near
Mexico
City. They would then travel together to a desert field station
near Ciudad
Obreg?n in northwestern Mexico to study the current crop of
experimental
wheat cultivars, planted at the beginning of winter.
But not this year. For the first time in half a century, the
research
centre that helped to sow the seeds of the 'green revolution'
of the 1960s
and '70s has been forced to skip a cycle of wheat breeding trials,
because
of a lack of money. More than half of CIMMYT's fields in Obreg?n
lie
fallow, and the trainee plant breeders are staying at home.
CIMMYT is not alone. All over the world, conventional plant
breeding has
fallen on hard times, and is seen as the unfashionable older
cousin of
genetic engineering. "Plant breeding is getting dumped along
the wayside
for not being sexy enough," claims Greg Traxler, an agricultural
economist
at Auburn University in Alabama. Government funding of plant-breeding
research has all but dried up in the United States and Europe,
and the
World Bank and donor nations have recently slashed their support
for the
Consultative Group on International Agricultural Research (CGIAR),
the
international research consortium of which CIMMYT is a part.
Meanwhile, a steady push by companies to claim exclusive commercial
rights
to new plant varieties has progressively tied the hands of publicly
funded
efforts at crop improvement. If this trend isn't halted, some
experts
claim, tomorrow's supercrops may end up like many of today's
medicines:
priced out of the reach of much of the developing world's growing
population. "We are headed down the same path that public-sector
vaccine
and drug research went down a couple of decades ago," says Gary
Toenniessen, director of food security at the Rockefeller Foundation
in New
York.
Sowing success. Classical breeders improve crops simply by crossing
plants
with desired traits, and selecting the best offspring over multiple
generations. Sometimes they use chemical mutagens to disrupt
crop genomes,
in the hope that some of the resulting mutants will have useful
new traits.
Crosses may be as simple as letting two plants grow together,
or they may
require pollination by hand. And for crops such as wheat, one
parent must
first be emasculated to prevent self-pollination. In some ways,
breeding is
like accelerated, targeted evolution, and as long as test crops
and seed
banks are maintained, the possibilities can never be fully exhausted.
These methods, applied intensively at CIMMYT and the International
Rice
Research Institute (IRRI) near Manila in the Philippines, provided
the
impetus for the green revolution. Breeders produced dwarf varieties
of
wheat, maize and rice that were less likely to fall over in
wind and rain,
and which could carry larger seeds. Thanks to these varieties,
farmers
could use more fertilizer without risking losing their crops,
and grain
harvests in some areas have doubled or even trebled over the
past three
decades.
Central to CIMMYT's success in wheat was the practice of 'shuttle
breeding', in which two seasons of plant selection could be
completed in
one year. Grain would be rushed from the fields in Ciudad Obreg?n
after the
harvest in April for summer planting in Toluca, near Mexico
City.
This year's cancellation of the Obreg?n end of the shuttle was
part of a
10% reduction in CIMMYT's programmes in the face of budget cuts,
says the
centre's director general, Masa Iwanaga. This was a result of
the reduction
in support for the CGIAR, which supports CIMMYT, IRRI and 14
other
agricultural research centres around the world.
Whereas the CGIAR's funding crisis has come to a head in the
past couple of
years, exacerbated by the global economic downturn, the world's
academic
plant-breeding labs have suffered steady attrition over a far
longer
period. Molecular genetics and transgenic technologies hold
great promise
for crop improvement, and have consumed a growing portion of
the limited
funding pie. University administrators have reinforced this
trend, tending
to replace retiring plant breeders with molecular geneticists
who are more
likely to produce high-profile journal articles.
Changes in the intellectual-property environment have also taken
their
toll. From the late 1960s onwards, developed nations introduced
a legal
framework of plant breeders' rights, giving new varieties and
cultivars
patent-like protection. The goal was to stimulate innovation
in corporate
labs, but the reforms also meant that public-sector breeders
were no longer
free to tinker with plants grown from commercial seed. "Plant-variety
protection was the death knell for public breeding programmes,"
says
Michael Gale, head of comparative genetics at the John Innes
Centre in
Norwich, Britain's leading public plant-science research institute.
Root of the problem. The figures reinforce Gale's view: until
the 1960s,
breeding for crop improvement was largely a public endeavour,
but a survey
of US plant scientists in the mid-1990s found more than twice
as many
breeders in the commercial sector than at universities and government
agencies combined1. And although breeders' skills are still
alive in the
private sector, they are now working to subtly different ends.
For seed
companies and agribiotech firms, the top priority has been developing
crops
that can maximize profits from the intensive agricultural practices
that
are widely used in the developed world. Sadly, there is less
money to be
made in seeding a second green revolution for the world's poor.
In recent years, of course, the big news in the commercial and
public
sectors has been transgenic technology, rather than conventional
breeding.
Genetically modified (GM) crops that are resistant to the effects
of
broad-spectrum herbicides or that carry genes for insecticidal
toxins have
been widely planted across North America ? but simultaneously
shunned by
European consumers, who are deeply suspicious of the technology.
The welter
of media coverage has obscured recent achievements in classical
breeding,
and although breeders generally view transgenics as a valuable
tool, they
stress that conventional breeding is far from obsolete.
In fact, for many GM crops, there is a comparable conventionally
bred
variety. The seed company Pioneer Hi-Bred, based in Des Moines,
Iowa, for
instance, produces a conventional, herbicide-resistant oilseed
rape, or
canola, that has similar advantages for weed control as its
GM
counterparts. And whereas the GM 'golden rice'2, engineered
to contain a
gene that boosts the production of vitamin A by people who eat
its grain,
has attracted much publicity, conventional breeding is also
being deployed
to improve the nutritional value of this staple crop. IRRI has
produced a
cultivar of rice called IR68144 that bears grain rich in iron3,
and so
could be used to combat anaemia. Even for crops such as the
banana, which
is unable to reproduce sexually without specialist human intervention,
conventional breeding may still have a role to play (see "Bananas
in the
fertility clinic").
What's more, the GM crops developed so far generally involve
only the
addition of a single gene. Looking to the future, it's unclear
whether
complex traits, which are thought to involve multiple genes,
will be
amenable to manipulation through genetic engineering. "In the
long term,
you need heat tolerance, salt tolerance, greater yield and so
on," says
Paul Gepts, a crop geneticist at the University of California,
Davis. "Some
say you can do it with genetic engineering, but we just don't
know how
those systems work and how those genes interact." By contrast,
practical
experience has shown that conventional breeding can be used
to improve a
suite of subtle traits simultaneously.
All of this makes Donald Duvick, who was head of research at
Pioneer
Hi-Bred until his retirement in 1990, concerned about the future
of crop
improvement should the agribiotech giants lose their enthusiasm
for
transgenics. "I worry that the results will be so far in the
future that
industry will say 'we can't wait that long'," he says. If so,
the depleted
public-sector effort in plant breeding may be ill-equipped to
take up the
slack.
There are already hints that some companies are pulling back
from long-term
investments in high-tech crop improvement. Only last month,
the Swiss-based
multinational Syngenta closed its Torrey Mesa Research Institute
near San
Diego, which was a major force in crop genomics. And both Syngenta
and its
US rival DuPont, which owns Pioneer Hi-Bred, have recently withdrawn
funding from the John Innes Centre. "The industry is in turmoil,"
says Gale.
Against this sombre background, can anything be done to safeguard
future
progress in crop improvement by reviving the science of plant
breeding in
the public sector? There is no easy answer, but some experts
suggest that
the future lies in boosting the power of conventional breeding
by marrying
it to genomic and other molecular-genetic techniques, while
making a
concerted effort to break with the proprietary approach to intellectual
property that is currently blighting the field.
Jorge Dubcovsky's genetic techniques aim to give traditional
breeding a
technological boost. One beacon of hope comes from a consortium
of
researchers at 12 institutions headed by Jorge Dubcovsky, a
wheat molecular
geneticist at the University of California, Davis. Its primary
tool is
'marker assisted selection' (MAS). This technique, enthusiasts
claim, could
offer to plant breeding what the jet engine has brought to air
travel.
Traditionally, breeders have relied on visible traits to select
improved
varieties. For pest resistance, for example, that means examining
mature
plants in the field over successive generations to see which
survive best
in the face of attack by pests, before carrying out new crosses.
MAS,
however, relies on identifying marker DNA sequences that are
inherited
alongside a desired trait during the first few generations.
Thereafter,
plants that carry the trait can be picked out quickly by looking
for the
marker sequences, allowing multiple rounds of breeding to be
run in quick
succession.
Superior breeding. MASwheat, as the consortium is known, aims
to select for
23 separate traits in wheat, conferring resistance to fungi,
viruses and
insect pests. Its members also hope to breed the grain to produce
bread and
pasta of superior quality. Notably, the consortium is making
all of its
marker sequences and research protocols freely available. "If
you go to our
website, you have all the tools to do this anywhere in the world,"
Dubcovsky says.
For wheat, this admirably open approach was relatively easy
to adopt,
because it is one of the few crops to remain largely in public
hands.
Because wheat is self-pollinating, many farmers simply plant
a portion of
their harvest each year, safe in the knowledge that it will
retain its
desirable characteristics. Not surprisingly, this has restricted
the
interest of commercial seed producers, who don't see a robust
market for
their products.
Elsewhere, however, intellectual property is creating a heavy
burden, with
universities and other institutions facing barriers to the free
exchange of
seed, and restricted access to cutting-edge molecular technologies.
"I wish
it would all go away," says Kent McKenzie, director of the California
Rice
Experiment Station, which develops new varieties of the crop
in its test
fields at Biggs, north of Sacramento.
Extending the MASwheat consortium's approach to other crops
may require
public institutions to band together to end the practice of
granting
exclusive licences to individual companies each time they develop
a
powerful technology for crop improvement. To this end, Toenniessen
has been
meeting with representatives of ten 'land grant' universities
? which form
the backbone of agricultural research in the United States ?
to hammer out
a plan. "If those in the public sector worked collectively,
they could
solve their problems," says Toenniessen. He hopes to pioneer
the approach
in speciality crops such as peanuts, broccoli, lettuce and tomatoes,
in
which the seed and agribiotech industry does not have strong
commercial
interests.
Free for all: Richard Jefferson wants to put crop improvement
within the
reach of poor farmers. Richard Jefferson would go further. His
Center for
the Application of Molecular Biology to International Agriculture
(CAMBIA)
in Canberra, Australia, is trying to put cutting-edge technology
for crop
improvement directly in the hands of developing-world scientists
and
farmers, rather than leaving them to depend on the continued
health of labs
in rich countries. "The money is drying up and that is not going
to
change," he says. "We need to rethink the way crop improvement
is done."
In part, Jefferson says, this will involve the transfer of transgenic
technologies. But extending access to molecular-genetic enhancements
to
conventional breeding methods will also be crucial. Researchers
at CAMBIA,
for instance, have developed a DNA microarray that will boost
MAS. In many
crops, it is difficult to search for specific genetic markers,
because very
little of their DNA has actually been sequenced. But by immobilizing
fragments of DNA from a variety of cultivars on a microarray
and then
seeing which of them bind to DNA sampled from individual plants,
it is
possible to look for the presence of genetic markers in these
plants in the
absence of any sequence information4.
This technology has already been adopted by the International
Center for
Tropical Agriculture in Cali, Colombia, for cassava improvement.
"It is
extremely useful," says Joe Tohme, the centre's director of
biotechnology.
By making such techniques freely available, and allowing scientists
anywhere in the world to tinker with and improve them at will,
Jefferson
hopes to speed progress. Essentially, he wants to create a crop-improvement
counterpart to the 'open-source' software movement that has
managed to
flourish alongside the proprietary approach of giants such as
Microsoft,
which keep their programs' codes under wraps.
'Open-source molecular agronomy' is certainly a sexier label
than
conventional plant breeding. But will it have sufficient cachet
to reverse
the current decline in public-sector crop improvement? The food
supply for
future generations in the developing world could hinge on the
answer.
References
1. Frey, K. J. National Plant Breeding Study (Iowa Agric. Home
Econ. Exp.
Station, Ames, Iowa, 1996).
2. Ye, X. et al. Science 287, 303-305 (2000).
3. Glahn, R. P., Chen, S. Q., Welch, R. M. & Gregorio, G.
B. J. Agric. Food
Chem. 50, 3586-3591 (2002).
4. Jaccoud, D., Peng, K., Feinstein, D. & Kilian, A. Nucl.
Acids Res. 29,
25e (2001).
5. Remy, S., Francois, I., Cammue, B., Swennen, R. & S?gi,
L. Acta
Horticult. 461, 361-365 (1998).
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