Transcript PowerPoint Presentation - Yields increase annually for

Yield Trends
and
Genetic Potential
Donald N. Duvick
Johnston, Iowa
Crop yields increase
annually in many nations
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Changes in cultural methods (e.g., fertilizer
kinds and amounts, plant density, and weed
control) are responsible for about 50% of
yield gains
Genetic improvements are responsible for
another 50% of the yield gains
The culture-to-genetics ratio varies from crop
to crop and region to region
On-farm yields: corn and
soybeans in North America
Bruulsema et al, Better Crops 84 (2000): 9-13
On-farm yields: wheat in UK
Austin, Crop Sci. 39:1604-1610 (1999)
On-farm yields: wheat global
Calderini and Slafer, Field Crops Research 57(1998) 335-347
Yield gains from cultural
inputs may be leveling off

In industrialized countries —
 Environmental
concerns mitigate against
further increases in application rates for
fertilizers and/or herbicides and insecticides
 Weed control is nearly absolute, although it
could be less effective in the future as weeds
develop resistance to intensively used
herbicides
DEDHAM, Iowa — By the time the Raccoon
River winds through the western hills here,
passing corn fields and livestock pens before
reaching Des Moines miles to the east, it is so
polluted the city has to put it through a special
nutrient filter to meet government standards for
drinking water.
The culprits are not industrial plants or mines
belching toxins into the river. They are Iowa
farms, which send fertilizer and animal wastes
into the groundwater and into the river. (New York
Times, February 10, 2002)
Fertilizer N on wheat in UK
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Austin, Crop Sci 39:1604-1610 (1999)
Fertilizer N on corn in USA
Source: USDA-ERS:Fertilizer Use and Price Statistics
160
Nitrogen used on corn, rate per fertiliz ed acre
receiving nitrogen, selected States
140
N, lb/A
120
100
80
60
40
y = -0.1521x2 + 603.57x - 598764
R2 = 0.9009
20
0
1960
1965
1970
1975
1980
Year
1985
1990
1995
Wheat yields since 1985
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Calderini and Slafer, Field Crops Research 57(1998) 335-347
Yield gains from cultural
inputs may be leveling off

In developing countries —
 Intensive
production inputs may have adverse
agro-ecological impact
 In high-yield regions, reduced or no yield
increase from increased applications of fertilizer
Rice yields since advent of
“Green Revolution”
Pingali, et al., “Asian Rice Bowls, The Returning Crisis? (IRRI, 19970
Consequently —
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Plant breeding may have to bear a much
greater share of responsibility for yield
gains in the years to come
Genetic yield gains continue
in most crops
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Gains primarily are in grains and legumes
grown for the commercial market
Gains primarily are for crops bred by
professional breeders, public and private
Gains in yield to date have not been
materially aided by biotechnology
Gains in yield are linear and show little or
no sign of leveling off
Genetic gain in rice: IRRI
Peng et al, Crop Sci. 39:1552-1559 (1999)
Genetic gain in wheat: UK
Austin, Crop Sci. 39:1604-1610 (1999)
Genetic gain in wheat: USA
Adapted from Donmez et al, Crop Sci. 41:1412-1419 (2001)
Genetic gain in wheat:
Mexico (CIMMYT)
Reynolds et al., Crop Sci. 39:1611-1621 (1999)
Genetic gain in soybeans:
USA (Maturity Group II)
Wilcox, Crop Sci. 49:1711-1716 (2001)
Genetic
gain
in
soybeans:
USA
Wilcox, Crop Sci. 49:1711-1716 (2001)
Genetic gain in corn: USA
Adapted from Duvick in, Developing drought- and low N-tolerant maize, CIMMYT (1997)
Genetic gain in corn: USA
Castleberry et al., Crop Sci. 24: 33-36 (1983)
Genetic gain in corn: USA
Duvick and Cassman, Crop Sci. 39:1622-1630 (1999)
Genetic gain in corn: USA
Duvick and Cassman, Crop Sci. 39:1622-1630 (1999)
Corn: Drought
tolerance,
USA
Duvick, personal communication (2002)
Drought is drought
Drought tolerance, 1930s genetics
Drought tolerance, 1990s genetics
Wheat: Irrigated performance versus ...
S. Rajaram, personal communication
Wheat: Drought performance
S. Rajaram (CIMMYT), personal communication (2002)
Yield Ceilings?
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At what point can on-farm yields go
no higher?
Will theoretical “yield potential”
calculations predict that point —
the yield ceiling?
Corn: Yield ceiling?
Duvick and Cassman, Crop Sci. 39:1622-1630 (1999)
Corn: Yield ceiling?
Duvick and Cassman, Crop Sci. 39:1622-1630 (1999)
Rice: Lowered ceiling?
Peng, et al., Crop Sci. 39:1552-1559 (1999)
Corn: What ceiling?
Source: Iowa Soybean Association (2002)
Iowa Master Growers
Champion Non-irrigated
450
400
Bushels per acre
350
300
250
200
150
100
50
0
1950
y = 0.0099x3 - 58.854x2 + 116170x - 8E+07
R2 = 0. 9235
1960
1970
1980
1990
Year of Contest
2000
2010
Yield potential: theoretical
or practical
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Theoretical calculations require
assumptions that may become outdated
as farming practices change
Estimates of practical yield potential
require constant updating also, as farming
practices change
An eternal constant: Farmers want more
yield and greater stability of yield
How to increase practical
yield potential?
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Change plant architecture
Improve “harvest index”
Increase “crowding comfort”
Increase efficiency in utilizing soil
nutrients
Increase tolerance to disease and insect
pests
Increase tolerance to abiotic stress
Plant architecture
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Rice, wheat and corn now have
more upright leaves
Corn has smaller tassels
Rice and wheat are designing
“New Plant Type” to have larger
panicles/spikes and larger stems
Corn: tassel size,
leaf angle
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1930s
1990s
Corn: leaf angle
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1930s
1990s
Harvest Index
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Rice and wheat have increased harvest
index since 1960s, but no further change is
expected
Corn has not increased harvest index
(when genotypes are at optimum density)
Rice, wheat, soybeans, and corn currently
increase yield by increasing biomass and
thereby increasing the number of
grains/kernels per unit area
“Crowding comfort”: Soybeans
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“As the plant population
increased from 33 to 50 to 100
plant m-2 the yield of new (post1976) cultivars became
increasingly greater than that of
the old (pre-1976) cultivars.”
(Specht, et al., Crop Sci. 39:1560-1570. 1999)
Increased efficiency
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in using (or supplying) soil nutrients: soybeans
Specht, et al., Crop Sci. 39:1560-1570 (1999)
Tolerance to disease and
insect pests
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Conventional breeding has been effective and will
continue to be effective in providing resistance to most
disease and insect pests
Durable resistance is the greatest need
Biotechnology, e.g. with transgenics, can produce
resistance in some cases where none is found in the
crop species or its near relatives
Molecular biology, longer term, will produce theory and
genetics for improved durable resistance
Tolerance to corn borer (pre-Bt)
1940s genetics
1970s genetics
Tolerance to abiotic stress
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For all crops, increased yield is associated with
increased tolerance to abiotic stresses such as:
Too hot
 Too cold
 Too wet
 Too dry
 Too much shade
 Too few nutrients
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Tolerance to abiotic stress
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There is no completely stress-free
environment
Therefore to breed for more tolerance to
any stress is to breed for higher yield as
well as for more stable performance
No cultivar is perfect, therefore possibilities
to breed for improved yield are always
present
The Future
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Will gains continue?
Will they meet global needs?
Will they be for the right crops
and right regions?
Yields can (will?)
continue to climb, but ...
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The cost per unit of improvement has risen
consistently during the past 100 years
Enthusiasm for production agriculture including
plant breeding consistently declines (in the nonfarm population of the rich countries)
Funding for public sector plant breeding (and for
public agricultural research in general)
consistently declines worldwide
Yields can (will?)
continue to climb, but ...
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Attitudes toward private sector plant breeding
polarize toward condemning it or assuming that
“it can do it all”
Widespread fear of genetic engineering for plant
breeding is transforming into a fear of plant
breeding in general
Gains cost more
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Thus we seem to require
increasingly greater numbers of
maize breeders to maintain a
constant rate of improvement
in yield.” (Duvick, in Genetic
Contributions to Yield Gains of five Major
Crop Plants. CSSA. 1984)
Higher yields not needed
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“The biotechnology industry claims it holds the
answer to world hunger: high technology to
increase production. But according to the United
Nations Food and Agriculture Organization
(FAO), this badly misstates the problem. There is
no shortage of food in the world. Per capita food
production has never been higher.” Advertisement in
New York Times, October 11, 1999, by Turning Point Project, a
coalition of more than 60 non-profit organizations.
Funding declines
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“Expenditures on agricultural
research in the public sector,
including the International
Agricultural Research Centers
(IARCs) have stagnated and in some
cases, declined sharply in recent
years.” (Maredia and Byerlee, Agricultural
Economics 22:1-16. 2000)
Parasite or protector?
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“… government does the costly, basic and
innovative research, while big companies pick
up the profits in the marketplace.” (Fowler and
Mooney, “Shattering: Food Politics, and the Loss of Genetic
Diversity”. 1990.”
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“Some question the need for continued public
funding [of agricultural research], thinking that
… the private sector will do the job.” (Pardey and
Beintema, Slow Magic. IFPRI Policy Statement. 2002)
Plant breeding
= genetic engineering?
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“Recently, in the state of Washington, usually known
for its progressive policies, strawberry plots and
greenhouses belonging to Washington State
University have been savaged, even though they
contained not one single transgenic plant! In fact,
nobody at that university has ever conducted
transgenic research on strawberries.” (Lurquin, The Green
Phoenix, A History of Genetically Modified Organisms. 2001)
Can breeding meet the
challenge?
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Predicted rates of increase in food demand during the
next 50 years tend to be larger than measured genetic
gains in yield during the past 50 years
Future food needs are greatest in regions where
breeding progress has been slowest
But with adequate political and economic support, yield
gains could be greatly increased in the most needy
regions
Can breeding meet the
challenge?
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Plant breeding cannot do the job
alone
It must be preceded and undergirded by the proper political and
economic climate
Tailor breeding to the
place and people
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Breeding techniques suited for commercial agriculture
in industrial countries will work also for commercial
agriculture in developing countries
But many farming people (2 billion?) in “traditional
agricultural areas” (poor land, poor economy) do not
farm commercially and have different and highly
diverse needs for variety improvement.
Participatory plant breeding may be best suited for
such “traditional” farmers
Participatory Plant Breeding
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Several variations, all emphasize
decentralization
 strong farmer participation
 on-farm testing
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Professional breeders advise but
do not dictate
Goal is to produce varieties that
meet local farmers’ needs
 that farmers can reproduce
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What about biotechnology?
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Biotechnology will not enable spectacular
increases in yield in the near term
Biotechnology will be essential over the long
term to help yield gains keep in step with global
food needs
Biotechnology in the near term will be more
useful in developing countries than in industrial
countries, if it can help breeders add badly
needed kinds of disease and insect resistance
What about biotechnology?
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Biotechnology’s greatest contribution to plant
breeding will be to increase the depth of
knowledge about gene action and how to modify
it to suit needs of farmers
Biotechnology causes contrasting social
problems at present; it arouses fears and raises
hopes in two types of people:
 Type
1: great fear of repressive monopolies
 Type 2: great hope of high profit margins
 Both types may be wrong
In conclusion:
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Plant breeding, properly supported and wisely conducted,
can help to increase food production in step with diverse
needs of a growing global population
Breeding must be done with care to produce products
That farmers want and can eat and/or sell
 That grow well where the farmers farm
 That respond well to the way the farmers farm
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As breeders would say: Pay attention to GxE
Carpentry 101:
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Plant breeding is a three-legged stool:
Leg 1: National and state public
sector programs
Leg 2: International public sector
programs
Leg 3: A diverse assemblage of
private sector programs
The stool supports the farmer