Preventing Mycotoxins in the Field

Peter J. CottyAgricultural Research Service, United States Department of Agriculture

School of Plant Sciences, University of Arizona, Tucson

Mycotoxins: Triple Threat to African DevelopmentWoodrow Wilson International Center for Scholars

Washington, DC, 14 February, 2012

During Crop DevelopmentIrrigation, Weed Control, Fertilize

Best cultivars, Insect Control

During transportRapid, Dry, No Damage

During ProcessingSort, Cull, Discard, Add binders.

During StorageDry, prevent moisture, cool

Prevent damage: insects, rodents

Prevent Formation of Dangerous Aflatoxin Levels Protect Crops Until Use

A Single application at 10 kg/hectare is enough to consistently reduce aflatoxins in maize, groundnut, and other crops.

Nigeria

Atoxigenic Isolates Occur Naturally on Crops

Isolates useful for biocontrol are endemic in and adapted to target agroecosystems.

Per

cent

of

A. f

lavu

s

0

10

20

30

40

50

60

1 2 3 4 5 6

Field 1 Field 2

Aflatoxin Produced in Culture (log ppb)

Aflatoxin-ProducingPotential

Field 1 = Low,3,400 ppb

Field 2 = High,54,000 ppb

Aflatoxin Production by A. flavus from Two Fields

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 vulnerability of crops to aflatoxin contamination

As Applied

AfterFungal Growth

Either Sorghum, Wheat, or Barley are used.

The grain is killed by cooking before use.

Sorghum is used in Africa.

Afla

toxi

n B

1 (ng

/g X

10,

000)

Isolates (%) in Applied Atoxigenic Strain

0123456789

0 20 40 60 80 100

r = 0.71, P = 0.0001

Dots Represent Values for Replicate Plots

Aflatoxin in Crop versus Atoxigenic Incidence

Cotty, 1994. Phytopathology:1270-1277.

Aflatoxin (ppb)Area Samples (#) AF36 (%) Mean Range

GraysonNorth 17 96 a 12 a 0 to 48

GraysonSouth 16 98 a 15 a 0 to 38

GraysonControl 8 24 b 230 b 5 to 530

Commercial Maize: North Central Texas 2008

Means in the same column with different letters are significantly different by Tukey’s HSD test, P < 0.001.

0%

20%

40%

60%

80%

100%

Bark

ley

Shar

p

Stuh

r

Bark

ley-

N

Shar

p-20

4W

Stuh

r-3W

Bark

ley-

29

Bark

ley-

95N

Bark

ley-

95S

Shar

p-20

5W

Shar

p-20

1

MV:

0.3

mi-S

E

YV: 0

.6 m

i-NE

MV:

0.7

mi-E

MV:

1.2

mi-W

Treated

Diagonal

Adjacent

Other

Incidence of AF36 within Aspergillus flavus Communities Prior to and One Year After Application

Inci

denc

e of

AF3

6= 1997 = 1996 =1997 & 1996 differ

Fungi Resident in the Soil

82%

53%

96%100%

0% 0% 0% 1% 17% 11%

77%74%

0%

20%

40%

60%

80%

100%

Par

ham

Soi

l

Rut

herfo

rdS

oil

Par

ham

Cor

n

Rut

herfo

rdC

orn

Par

ham

Cor

n

Rut

herfo

rdC

orn

2008 2008 2008 2008 2009 2009

Perc

ent o

f Asp

ergi

llus

flavu

s Grayson County, Texas: Carry Over to the Second Year Crop

= Atoxigenic isolate AF36

= S Strain, produces very high aflatoxins

Crop Treatment Year

Crop Year After Treatment

Soil Before Treatment