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United States Department of Agriculture

Agricultural Research Service

Mycotoxin Research
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1 - Overview
2 - Biological Control of Aflatoxin
3 - Fungal Invasion of Peanuts
4 - Fungal Population Biology
Fungal Invasion of Peanuts


Peanuts fruit underground and are in direct contact with soil populations of Aspergillus flavusand Aspergillus parasiticus, the two fungi responsible for producing aflatoxin in peanuts.

 Peanut plant with soil removed to show pods.

 Aspergillus flavus

Aspergillus parasiticus

 Aspergillus flavus

 Aspergillus parasiticus

A laboratory procedure has been developed in which viable peanut seeds are wounded and inoculated with soil directly from the field.  This research has shown that despite low spore densities in soil, aflatoxin-producing fungi preferentially invade peanuts over other soil-inhabiting fungi.  Invasion is greatly influenced by seed moisture and soil temperature.

Aspergillus infected kernel

Aspergillus infected kernel

Seeds colonized by Aspergillusspecies

 Chart showing the effect of soil population density on peanut infection

Effect of soil population density on peanut infection

This procedure is currently being used to assay different nontoxigenic A. flavusstrains for their ability to reduce aflatoxin in biological control.

Ability of eight nontoxigenic Aspergillus flavusstrains to inhibit aflatoxin production by specific aflatoxin-producing strains using the peanut seed assay
 

   Nontoxigenic strains
Aflatoxin production by strain F35  
Significant reduction of aflatoxin: Strain A > B > C > D > E > F 
No significant reduction in aflatoxin: Strain G, H
   
Aflatoxin production by strain F14  
Significant reduction of aflatoxin: Strain G > C > E > A > D > F> H > B
   
Aflatoxin production by strain F86  
Significant reduction of aflatoxin: Strain H > A > C
No significant reduction in aflatoxin: Strain B, E, D, G, F
   
Aflatoxin production by strain F44  
Significant reduction of aflatoxin: Strain C > A > D > G > E > F
No significant reduction in aflatoxin: Strain B, H
 
 F= Biological control strain in current use

For more information contact Bruce Horn.

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Last Modified: 1/6/2010
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