Wheat Yield Barrier
"Yield Barrier" In Wheat
Experts From 8 Countries Warn Of "Yield Barrier" In Wheat; Report Calls For
New Strategies For World's Crucial Crop
As Population Grows, Wheat Yields Fail to Keep Pace
WASHINGTON, D.C., October 23, 1996 - As the world population booms, the staff
of life for millions _ wheat _ may not be keeping pace, according to a new
report released today by the Mexico-based International Maize and Wheat
Improvement Center (CIMMYT). The report lays out a plan for breaking the "yield
barrier" in wheat. It was developed by the world's most respected wheat
scientists from 8 different countries and constitutes a synthesis of the most
innovative thinking for increasing wheat yields into the next millennium.
Among other strategies, the scientists call for a global quest for genetic
diversity in wheat, tapping into wild wheat relatives and wheat collections of
countries around the world _ from Australia to Russia _ to find new,
"In the 1960s and early 1970s, when financial backing for agricultural research
was in its heyday, wheat yields grew at a level of about 100 percent," said
Timothy Reeves, Director General of CIMMYT. This was based on the combined
effect of genetic improvement and enhanced crop husbandry (collectively know as
the "Green Revolution"). "While the population is growing at a rate of 2.5
percent per year, these yields are now increasing only 1 percent a year," said
Reeves. With wheat projected to feed more people than any other crop in the
21st century, stagnating wheat yields could put many at risk of hunger and
poverty. Science must go further and find new answers for boosting wheat
yields, especially since a population equivalent to Australia's is added to the
earth every 12 weeks."
According to Matt Reynolds, Wheat Physiologist at CIMMYT and lead author of the
report, there are three possible options for increasing wheat yields _
increasing the land area that is sown to wheat; increasing the use of
fertilizer, irrigation, and other inputs; or increasing the yields of wheat so
that more wheat can be harvested on the same land, using the same amount of
inputs. "We have selected the last option because the first and second options
come with high environmental price tags," said Reynolds.
The report lays out six main scientific strategies to break the yield barrier
1.) Exploiting the genetic diversity of wheat _ Though scientists have made
great strides in wheat research, there may be unknown genes that could push
wheat yields up further while still producing good-tasting grain and adaptable
plants. Wheat scientists are launching a worldwide search for genetic diversity
in order to find such new genes.
"Hundreds of thousands of years ago, wheat was a wild grass," said Reynolds.
"By a chance cross of two wild grasses, something similar to wheat was created.
Early humans then found this plant and began to grow it, selecting for the best
grain or for adaptability. Thousands of years later, breeders have applied the
best in science to create today's elite varieties of wheat _ thoroughbreds _ in
the fight against hunger.
"We are going back to wild grasses _ wheat's distant relatives _ and even to
alien, nonwheat plants to find even better genes than we have now," continued
Reynolds. "We can use biotechnology _ genetic maps and markers _ to identify
good characteristics for yield, adaptability, resistance to pests and diseases,
and, of course, good grain size and taste."
Scientists will produce new "synthetic" wheats, which are formed by crossing a
distant relative of wheat _ such as goat grass _ with elite durum wheats.
Synthetic wheats will serve as a bridge for moving additional yield-enhancing
traits from distant relatives to modern bread wheats.
The new wheat strategy also calls for scientists to scan the world wide pool of
elite wheat varieties. CIMMYT will serve as an information clearinghouse, and
will make several different kinds of innovative crosses in the lab and in
experimental fields. Scientists have been crossing wheats grown in cool
climates (winter wheats) with wheats grown in warmer climates (spring wheats)
for years. However, there are still vast untapped gene pools, particularly in
the states that formerly made up the Soviet Union. Crossing them enhances
genetic diversity and may create even more high-yielding plants.
2.) Developing a new wheat plant prototype _ In the 1960s, scientists
dramatically changed the architecture of wheat plants in an advance called
"semi-dwarfing." Semi-dwarfing shortened plants, allowing them to make use of
fertilizers and irrigation without falling over. This advance also directed
more of the plant's energy and biomass to grain as opposed to leaves and roots.
Wheat scientists are hoping to build on those advances by creating prototypes
possessing traits that will enable them to yield even more than current wheats.
3.) Testing the hypothesis that increasing the length of time for the
development of the immature wheat spike will produce a larger grain _ Just as
humans spend a longer time than any other animal in an immature state in order
to more intelligently adapt to their environment, scientists believe that
prolonging the spike development stage of wheat may result in more useful wheat
4.) Making better use of scientific selection criteria to identify useful traits
_ When scientists cross two wheat plants, they may end up with thousands of
offspring. However, the scientists can't currently identify all the
characteristics of the new plants. CIMMYT will be utilizing technologies that
will help identify the best plants early in the process; thus speeding the
5.) Better adapting wheat varieties to particular farming systems and styles
within regions of the world _ Scientists may be able to increase yields simply
by creating wheat plants that are better suited for the realities of particular
farming conditions in various regions.
6.) Exploitation of "hybrid" wheats _ Scientists will cross elite, pure bred
lines with each other, seeking a phenomenon called "heterosis," where the hybrid
offspring have tremendous advantages over either parent. However, unlike pure
breeds (normal varieties), hybrids do not breed. But if the offspring of
hybrids cross, heterosis does not occur because the two parent wheat varieties
involved must remain pure. Farmers must therefore purchase new seed each year.
Though expensive, the yield gains from hybrids may offset the cost of purchasing
new seed each year. China, for example, chooses to encourage hybrid rice
"These strategies should help us to break the yield barrier in wheat, but they
will need support," said Reeves. "One of the main causes of stagnating wheat
yields may be the declining public and private investment in agricultural
research. Today, CIMMYT's budget is 30 percent less than it was ten years ago,
and, after factoring for inflation, we have 50 percent fewer funds to conduct
research. Without these funding cuts, we may have already made more headway
against the yield barrier."
CIMMYT employs more than 100 scientific staff from 39 countries together with
more than 800 support staff. Its experimental research station is located
outside of Texcoco, an hour from Mexico City. CIMMYT scientists work with
national research systems in developing countries worldwide. Financial backing
for CIMMYT's work comes from public and private foundations as well as some 40
countries, with the majority of funds administered through the Consultative
Group on International Agricultural Research (CGIAR).