Abstract

Soil and un-husked maize samples were collected from 29 different locations belonging to three distinct ecological zones (Swat, Hazara and Peshawar) of Khyber Pakhtunkhwa, Pakistan. The samples were evaluated for the incidence of aflatoxigenic strains of Aspergillus flavus. The soil samples collected from Peshawar (100%) and Hazara (66%), and grain samples collected from Swat (64%) and Peshawar (55%) were severely infected with aflatoxigenic strains of A. flavus. The strains isolated from maize kernels of Manyar, Jalala (Swat zone), Palosi and Takkar (Peshawar zone) produced the highest amount of aflatoxin B1 (324 to 514 µg g^-1) and B2 (23 to 486 µg g^-1). Similarly, the strains isolated from soils of Bannu (Peshawar) and Huripur (Hazara) were prominent in B1 (662 to 1323 µg g^-1) and B2 (145 to 826 µg g^-1). Microbial analysis of the surface sterilized grains showed that the strains isolated from Jalala (Swat) and Palosi (Peshawar) samples were high in B1 (62 to 79 µg g^-1) and B2 (21 to 36 µg g^-1). It was concluded, therefore, that A. flavus from soil might contaminate maize crop, but not directly from the same field. The most probable contamination occurred through air borne spores. It is thus recommended that protection from air borne spore should be devised.

Key words: Aspergillus flavus, aflatoxin, ecology, maize crop, field, soil toxicology.