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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.

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.

Seeds colonized by Aspergillusspecies
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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