Developing crops become infected. Associated with crop damage (insect, Aflatoxin increases in mature crop. May occur before or after harvest.

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1 Biocontrol and other solutions: Addressing Aflatoxin in Sub--Saharan Africa Sub Peter J. Cotty Agricultural Research Service United States Department of Agriculture School of Plant Sciences University of Arizona, Tucson Ranajit Bandyopadhyay International Institute of Tropical Agriculture Ibadan, Nigeria

2 Aflatoxin Contam mination Occurs in Two Phases Phase I: Before Crop Maturity Developing crops become infected. Associated with crop damage (insect, bird, stress). Crop may exhibit BGYF (bright-greenyellow fluorescence). Favored by high temperature (night) and dry conditions. Phase II: After Crop Maturity Aflatoxin increases in mature crop. May occur before or after harvest. Seed is vulnerable until consumed. Associated with high humidity in the field, & improper crop storage or transportation. Rain on the mature crop increases contamination.

3 Aspergillus flavus occurs throughout warm regions. However, this fungus varies widely in several important traits.

4 Aflatoxin Production by Funga al Isolates in Liquid Fermentation 5 Log ng g/g (ppb) Isolates from One Agricultural Field

5 Fungi Vary Across Areas in Aflatoxin-Producing Ability Farmers apply atoxigenic strains to reduce the average aflatoxin-producing potential of fungi on farms & thus the vulnerabilit ty of crops to aflatoxin contamination. flavus Aflatoxin Production by A. flavus from Two Fields 60 Field 1 Field 2 50 Aflatoxin-Producing Potential 40 Field 1 = Low, 30 3,400 ppb Percent of A Aflatoxin Produced in Cult ture (log ppb) Field 2 = High, 54,000 ppb

6 As Applied After Fungal Growth

7 Aflatoxin in Crop versu us Atoxigenic Incidence Aflatoxin B 1 (ng/g X 10, ) Dots Represent Values for Replicate Plots Isolates (%) in App plied Atoxigenic Strain

8 Influences of Field Application of Atoxigenic A. flavus on: Aflatoxin, Infection, & Total A. flavus on the Crop at Harvest Aflatoxin B 1 (mg kg -1 ) Infection (%) A. flavus on crop (spores/g) Applied strain (%) Treated 0.3 b 1.03 a 23,949 a 100 a Control 81.8 a 0.85 a 28,949 a 7 b Values followed by a common letter do not differ significantly.

9 Commercial Maize Test: North Central Texas 2008 Area Samples (#) AF36 (%) Mean Range Grayson North Grayson South Grayson Control Aflatoxin (ppb) 96 a 12 a 0 to a 15 a 0 to b 230 b 5 to 530 Means in the same column with different letters are significantly different by Tukey s HSD test, P <

10 Aflatoxin Contamination: A Perennial Concern in Warm Climates Contamination is worse during dry periods. During droughts the zone containing contaminated crops enlarges. 35 N 35 S Zone with Perennial Contamination Risk

11 Atoxige enic Strains from Kenya More than 3,400 A. flavus isolates recovered from 263 ground maize samples obtained between 2004 and 2006 from the Eastern, Coast and Rift Valley 290 L strain isolates screened for aflatoxin-producing ability on maize 96 identified as atoxigenic and co-inoculated with toxigenic stain on maize 23 Strains that reduced >80% or members of VCG from 2 or more locations were further evaluated 12 atoxigenic VCGs (13 strains) selected for further evaluation under field conditions in Kenya The best atoxigenics from Kenya reduce aflatoxins in maize as good or better than the atoxigenics used in the US Probst, C., Bandyopadhyay, R., Price, L. E., and Cotty, P. J Identification of atoxigenic Aspergillus flavus isolates to reduce aflatoxin contamination of maize in Kenya. Plant Disease 95: Probst, C., Schulthess, F., Cotty, P.J Impact of Aspergillus sect. Flavi community structure on the development of lethal levels of aflatoxins in Kenyan maize (Zea mays). Journal of Applied Microbiology 108: Probst, C., Njapau, H., Cotty, P.J., 2007 Outbreak of an Acute Aflatoxicosis in Kenya in 2004: Identification of the Causal Agent. Applied and Environmental Microbiology 73:

12 Senegal Aflatoxin Reduction: 87% at harvest 38 Farms in 2 Zones Were Treated in 2010 Farmers threshing groundnut Farmers treating groundnut fields with AflaSafe

13 Nigeria

14 Aflatoxin Reductio on in Maize after AflaSafe Applic cation in Kaduna Zone Number of farmers Mean B-aflatoxin (ng/g) AflaSafe Control Reduction (%) Maigana Pampaida Lere Birnin-Gwari Mean

15 Aflatoxin reduction in 4 zones 4 months after poor sto orage in Nigeria % reduction in aflatoxin content in treated fields over control 85% 82% 99% 95% 800 Aflatoxin (p ppb) Control Treated Birnin Gwari 271 Lere Maigana Pampaida

16 Farmers in Nigeria treat maize and groundnut fields with AflaSafe Aflat toxin reduction at harvest: 2009: 80% 2010: 89% 56 to 73% carry-over of inoculum one year after application

17 Incidence of AF36 within Asp pergillus flavus Communities Prior to and One Ye ear After Application 100% Treated = 1997 = =1997 & 1996 differ 80% Fungi Resident in the Soil Adjacent 60% 40% Diagonal Other 20% 0% Incidencee of AF36 Barkley Sharp Stuhr Barkley-N Sharp-204W Stuhr-3W Barkley-29 Barkley-95N Barkley-95S Sharp-205W Sharp-201 MV: 0.3 mi-se YV: 0.6 mi-ne MV: 0.7 mi-e MV: 1.2 mi-w

18 100% 100% 100% 100% Yuma Valley, Arizona 75% 50% 75% Long-term Influences Suggest Area-wide e Programs may be Effective 50% 75% 50% 75% 50% 25% 25% 25% 25% 0% 0% 0% 0% Percent of the A. flavus Soil Community Composed of the Applied Atoxigenic Strain & the Highly Toxigenic S Strain Application M J J A S O N D J F M A M J J A S O N COTTON WHEAT D J F M A M J J A S O N D J F M A M J WHEAT MELONS = % Atoxigenic Strain = % S strain

19 Grayson County: Carry Ove er to the Second Year Crop 80% 60% 74% 77% 100% 96% 82% = S Strain = AF36 of Aspergillus flavus100% 40% 53% 20% 11% 0% 0% 0% 1% 17% 0% Parham Soil Rutherford Soil Parham Corn Rutherford Corn Parham Corn Rutherford Corn Percent o

20 Crops are infected by complex communities of diverse fungi We can influence aflatoxin-producing ability of fungal communities resident in production areas through crop rotations, agronomic practice, and by applying atoxigenic strains There are many atoxigenic strains Select strains best adapted to rotations, ecosystems, & climates Atoxigenics are Alread dy Present on the Crop Just increasing the frequency of endemic stra ains & natural interference with contamination Treatments have Long-Term Inf fluences & Cumulative Benefits More than One Crop May Be enefit From the Same Strain Atoxigenic Strains can be Appli ied Without Increasing Infection and without increasing the overall quantity of A. flavus on the crop & throughout the environment

21 Ranajit Bandyopadhyay, Plant Pathologist International Institute of Tropical Agriculture Ibadan, Nigeria