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Multidisciplinary Approaches to Reduce the Impact of Corn Aflatoxin on Texas
Dr. Joseph Awika – Food TechnologyDr. David Baltensperger – Soil and Crop SciencesDr. Youjun Deng – Soil MineralologyDr. Joe Dixon – Soil MineralologyDr. Tim Herrman – Grain Science / State ChemistDr. Tom Isakeit – Plant PathologistDr. Mike Kolomiets – Molecular Plant PathologyDr. Kyung-Min Lee – Cereal ChemistryMr. Kerry Mayfield – Corn BreedingDr. Seth C. Murray – Corn BreedingDr. Gary Odvody – Plant Pathologist (Corpus Christi)Dr. Tim Phillips - Toxicology and Food ScienceDr. Wenwei Xu – Corn Breeding (Lubbock)
Funding: Texas AgriLife, Texas Corn Producers Board, USDA, USAID, NSF, many others.
- Highly toxic compound produced by fungus Aspergillus flavus
- Toxicity at low concentrations:- 20ppb action level / above 500ppb must be destroyed- Potent carcinogen
- Pre-harvest production in corn kernels- Can also occur on corn in storage
What is Aflatoxin?
Dr. Gary Odvody
Interaction BetweenPathogen, Environment and Plant
Aspergillus flavus spores
Suitable environment
Susceptible host: corn& others
Disease Triangle
Infection / resistance
Vs.aflatoxin
production
Kerry Mayfield
- Drought / heat stress- High temperature/ low soil moisture- Especially after silking – enter silks- Corn maturation into increasing heat/ stress
- Insects- Primarily Lepidotera- Stalk borers- Corn earworm (CEW), Fall armyworm (FAW)
- Wounding- Aflatoxin accumulation variable:
- Within an ear - maybe a few kernels- Across a field – drought hot spots, field edge
- Late planting increases stress
Environments Favorable for Aflatoxin
Dr. Gary Odvody
Corn Yields and Aflatoxin
Aflatoxin Loss Liability 2008
Office of the State Chemist Sampling 2008
Kerry Mayfield
Aflatoxin levels in corn 2009Office of the Texas State Chemist
* The color indicates the highest reported incidence in a county.
≤ 20 ppb50 – 300 ppb300 ppb500 ppb
Dr. Tim Herrman & Dr. Kyung-Min Lee
Plant Breeding – find andincorporate genes or traitsfor A. flavus resistanceinto hybrids.
Integrated Pest Management –identify agronomic practicesthat reduce A. flavus.
Plant Pathology – identifydisease factors, developcompeting atoxigenic strains.
Remediation – Find binders orprocessing methods to reducethe toxin or toxin absorbance. Food Science/ Veterinary
Nutrition – Identify processingmethods that can reduceaflatoxin.
Pre-Harvest Aflatoxin Contamination• Texas 2008 corn farm gate value = $1billion (13th in Country) • $14 million loss liability from mycotoxins in 2008• Most elite US germplasm is highly susceptible in Texas • Breeding is one of the least expensive and least intensive methods
for reducing aflatoxin contamination • No identified sources of complete resistance to Aspergillus / aflatoxin• Test in multiple environments with inoculation
Percent (%) Acreage with Aflatoxin Claims 2008
Aflatoxin Resistance Differs Across Corn Inbred Lines and Hybrids
Weslaco
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
2000.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Genotype
Afla
toxi
n (n
g g
-1)
Genotype Pedigree6 (Tx772/CML326)-B-B5-B-B/ Tester8 LAMA2002-14-B-B/ Tester
Mayfield et al, 2007
Kerry Mayfield
Corn Breeding Pyramid for Reduced Pre-Harvest Aflatoxin Contamination
- Husk Coverage - Long, cover tips- Tight and thick
- Maturity- Flowering time- Days to maturity
- Kernal hardness- Ear nod (ear droop)- Earworm resistance- Drought tolerance
YIELDRow
number Kernel
size
Ear length
LodgingKernel density
StressResistance Stay Green
How do we separate
these various correlated
traits ?
QTL Mapping - RIL Hybrids
WE Oil
CS Oil
CC Oil
CS Protein
CS Starch
CS Log AF
WE Log AF
WE Nodded Ears
135 RIL Testcrosses (B73o2 x CML 161)College Station , Weslaco and Corpus Christi3 Replications 15 QTL detected in traits
Kerry Mayfield
Tx714 FR2128 Tx772Tx714 FR2128 Tx772
Aflatoxin levels can be reduced by deleting a lipoxygenasegene LOX5 in corn under field conditions in different genetic
backgrounds – natural diversity / non-GMO
Dr. Mike Kolomiets
Corn ears: rep 5 showing relative yield and insect damage at Corpus Christi, TX in 2006. Conventional hybrids are shown by row and traits are shown in
columnsVT Pro Yieldgard CB Non-Bt
Hyb 3
Hyb 2
Hyb 1
Avg. 646 ppb Avg. 898 ppb Avg. 1220 ppb
Dr. Gary Odvody
Dr. Tom Isakeit
Bentonites as Adsorbents
• Economically feasible
• Socially acceptable
• Environmentally friendly
Ines Mulder Maria Guadalupe Tenorio Arvide
Dr. Youjun Deng & Dr. Joe Dixon
Testing Natural Bentonites for Adsorption Sites and Ability
41 samplesUSA (TX, WY, MS, ID), Australia, Brazil, Japan, Korea, Mexico, Mozambique, Spain, Turkey, South Africa
D-spacing & Adsorption Sites
Poultry test (on going)
Dr. Youjun Deng & Dr. Joe Dixon
Animal FeedingProtected animals from diet levels as high as 7,500 ppb.
Ghana
Human Supplement
Reduced urine levels of AFM1 after 3-months
intervention
Deliverable Product
Dr. Timothy Phillips
Dioctahedryl Smectite (clay-based enterosorption) therapies for aflatoxins and other food contaminants. - No adverse health effects from consumption of NovaSil clay
Sampling Procedures are Extremely Important and Limiting
- Very Expensive to measure ( $8 to $100+ / sample)
- Heterogenous within an ear, field, grain bin, shipping container
To make progress:
- Need increased testing speed, accuracy, and sample size while reducing costs
- In research, best inoculation procedures must be followed
HPLC-Tandem MS Method (Aflatoxin)- Fast, compared with the tradition HPLC-Fluorescence
method
- Specific, quantitative, sensitive (LOQ 0.5 ppb)110309-Diluted in 20% MeOH
Time0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50
%
0
100
0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50
%
0
100
0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50
%
0
100
0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50
%
0
100
0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50
%
0
100AF-STD-7 MRM of 10 Channels ES+
331 > 245 (AFG2)3.00e4
2.11
2.28
AF-STD-7 MRM of 10 Channels ES+ 329 > 243 (AFG1)
2.29e52.31
AF-STD-7 MRM of 10 Channels ES+ 315 > 259 (AFB2)
5.84e42.52
AF-STD-7 MRM of 10 Channels ES+ 313 > 241 (AFB1)
5.06e52.85
AF-STD-7 MRM of 10 Channels ES+ TIC
8.23e52.85
2.312.11 2.54
Multiple reaction monitoring (MRM) of Aflatoxin B1, B2, G1 and G2 in LC/MS/MS
Dr. Tim Herrman & Dr. Kyung-Min Lee
Increase Throughput of Testing With NIRS
• Aflatest® is expensive and time consuming• Need to screen 5,000-10,000 samples/ year• Near Infrared Reflectance Spectroscopy (NIRS)
www.foss.dk
Run samples on NIRS
Identify informative samples from spectra
Test 10% of samples for aflatoxin and/or
Aspergillus
Develop calibration equation
Use NIRS calibration equation to predict
contamination levels
• Equation built using non-AG with a red (3/4) and val (1/4) sets
• 2,5,5,1 SCVD both vis and NIR (Rsq = 0.8071)
• Plot predicted vs. Full non-AG
NIRS Results – Rsq. = 0.8071
Safety and Monitoring of Respiratory Aflatoxin and Particulates
Apex Lite Personal Air Pumps were used to sample ~700L of air. Two of eight samples had detectible levels of
respirable particulates (.1mg/m3 ; .28mg/m3)
Clearvue Cyclone Air Cleaning
http://www.texascorn.org/images/E0117201/AflatoxinCenter_final_web.pdf
Aflatoxin Center of Excellence of the
SouthCreating Linkages between:-States (Alabama, Georgia, Mississippi, North Carolina, Louisiana, Texas)
- Commodity Groups
- Public Research Institutions
- Research, Education, Extension
Plant Breeding – find andincorporate genes or traitsfor A. flavus resistanceinto hybrids.
Integrated Pest Management –identify agronomic practicesthat reduce A. flavus.
Plant Pathology – identifydisease factors, developcompeting atoxigenic strains.
Remediation – Find binders orprocessing methods to reducethe toxin or toxin absorbance. Food Science/ Veterinary
Nutrition – Identify processingmethods that can reduceaflatoxin.