Amino acid analysis of GEM
germplasm
M. Paul Scott
USDA-ARS
Ames, Iowa 50011
pscott@iastate.edu
U.S. Corn Uses
National Corn Growers Association, 2004
Annual value:
$25 Billion
Feed/residual
Export
Ethanol
HFCS
Starch
Sweeteners
Cereal
Alcohol
Seed
Impact of increased ethanol
production
Corn Prices
Corn Acres
Soybean price
Gov’t Payments
Livestock income
Overall Farm income
N, P Lost to water
Soil Erosion
Up
Up
Down
Down
Slight decrease
Up
Up
Up
Source: WRI policy note,2006 Marshall & Greenhalgh
Annual meat consumption, per capita
(Source: FAO)
140
120
80
United States
60
World average
40
20
Year
1997
1993
1989
1985
1981
1977
1973
1969
1965
0
1961
kg
100
Food and Fuel
Petroleum
Grain
hydrocarbons
Starch Protein Oil
Transportation
Feed
Oilseeds
Protein Oil
Food
Food and Fuel
Grain
Starch Protein Oil
Petroleum
Oilseeds
Protein Oil
3.9 Billion Gallons
EtOH in 2005
13% of Corn crop
Transportation
146 Billion Gallons
Gasoline used/year in US
Feed
Food
A solution
Petroleum
Transportation
Lignocellulosic
Biomass
Grain
Starch Protein Oil
Feed
Grain +
Ethanol
Co-products:
DDGs
Oilseeds
Protein Oil
Food
What corn traits are important?
• Yield (insect, disease, drought …)
• N use efficiency
• What about quality traits?
Grain Ethanol Production
Protein
Fiber
Fat
Starch
10%
3%
4%
75%
Corn
Protein is concentrated
by ethanol production!
Problems are amplified!
Starch
2.7 gal/bu
$4.32/bu
Protein,
Fiber,
Fat
EtOH
Co-products:
DDGS,
Solubles
18 lb/bu
$0.68/bu
Protein
Fiber
Fat
Starch
30%
10-50%
10-20%
5%
Seed Fractionation
Osborn, 1924
Water
Albumins
Salt
Globulins
Alcohol
Prolamins
“Zeins”
Base
Glutelins
Seed Proteins
Embryo-vegetative
Endosperm-storage
Zeins
SDS-PAGE Coomassie Blue Stained
Zeins
• Zeins are so abundant that they have a
large impact on protein quality of grain
• Zeins are concentrated in ethanol coproducts so their impact is even greater
• Zeins are nutritionally poor for nonruminants
– They are poorly digested
– They are deficient in certain essential amino
acids
Amino acid levels
Corn vs. Egg
2.5
2
Maize
Soy
1.5
1
0.5
0
Lys His
Arg Asx Thr Ser Glx Pro Gly
Ala Cys Val Met
Ile
Leu Tyr Phe Trp
Nutritionally limiting amino acids
Methionine is the limiting AA in Poultry diets
Lysine is limiting in poultry and swine diets,
but can be supplemented inexpensively
Tryptophan is limiting in swine diets
What corn traits are important?
• Yield (insect, disease, drought …)
• N use efficiency
For Ethanol:
•Fermentable starch
•Protein quality
•Available P
Amino acid/
protein
For non-ruminant feed:
•Protein content
•Protein quality
•Available P
Absolute amino
acid level
Questions about biofuel coproducts
• How are differences in grain composition
reflected in co-product composition?
• How will co-products be improved by
processing?
• Can yeast components be used to
complement grain components in coproducts?
Evaluation of amino acid content of
GEM germplasm
• About 80 GEM accessions / year selected
for agronomics and past AA performance.
• Good lines are re-tested in subsequent
years
• Lys, Met, Trp, Index (Lys,Met,Trp)
• Checks:
– B101 (high Met)
– B45o2 (high Lys, Trp)
– B73xMo17, B73, Mo17, B45
Microbial assay for Met
Low
High
Met Concentration
Evaluation of amino acid
composition of GEM germplasm
M
0.20
0.15
0.10
M/protein
0.020
0.015
0.010
Two year Evaluation
Evaluation of amino acid
composition of GEM germplasm
0.016
0.20
M
0.16
0.14
0.12
0.10
0.08
0.014
M/protein
0.18
0.012
0.01
0.008
0.006
Four year evaluation
Highlights of the GEM AA program
• DKXL212:N11a-139 Index was significantly
higher than B73xMo17 in 4 yr tests.
• CHIS740:S1411a-783-2 Met/protein was not
significantly different that hi met check and
significantly higher than other checks in 4 yr
tests
• Seven XL370 and XL380 derived lines were not
different than high met check in 2 yr evaluations.
Recommendations
• Evaluation of hybrids
• Selection within GEM “lines”
• Development of synthetics for recurrent
selection
Divergent selection for amino acid
content
Long-term Selection for protein
content
Advantages:
Differences are
magnified by
selection in both
directions
Generate unique
material to answer
biological questions
Source: Dudley and Lambert (2004), Plant Breeding
Reviews 24, 7979-110
Recurrent Selection
Intermating of Selections
BS31HM C1
Selections
(5 ears)
BS31HM
Selections
(5 ears)
BS31
Evaluation of 50 ears
BS31HM
C1
BS31HM
C2
Divergent selection for AA Content
BS31
0.13
0.12
0.15
0.14
0.11
0.13
M (g/100g)
M (g/100g)
BS11
0.1
0.09
0.08
0.07
0.11
0.1
0.09
0.06
0.08
-4
-3
-2
-1
0 1
Cycle
2
3
4
-4
0.013
0.012
0.013
0.012
0.011
0.011
W (g/100g)
W (g/100g)
0.12
0.01
0.009
0.008
0.007
-3
-2
-1
0 1
Cycle
-3
-2
-1
2
3
4
2
3
4
0.01
0.009
0.008
0.007
0.006
0.006
-4
-3
-2
-1
0 1
Cycle
2
3
4
-4
0 1
Cycle
Acknowledgements
• Mike Blanco and the GEM team
• Merinda Struthers
• Funding from
USDA-ARS project funds
Thanks for your attention!