Abstract
Grains of important food and export crops in Africa are susceptible to contamination by toxin-producing moulds. Aflatoxins are mycotoxins associated with liver damage and cancer in humans and animals. These toxic substances are produced by fungi (such as Aspergillus flavus and Aspergillus parasiticus) in food and feed exposed to poor conditions during crop cultivation, storage or processing of harvest. The presence of aflatoxins in especially maize and peanuts in Kenya is of great concern. Recent developments in the application of atoxigenic strains of these fungi as biological control agents against toxigenic strains could be a solution to the problem. The objective of this study was to isolate, identify and characterize atoxigenic and toxigenic strains of A. flavus and A. parasiticus in Kenya, and investigate possible application of atoxigenic strains in control of aflatoxin levels in maize and peanuts. Fungal communities in soils of maize and peanut fields were examined to determine the distributions of aflatoxin-producing Aspergillus species and to identify endemic atoxigenic strains. 220 isolates belonging to A. flavus and A. parasiticus were collected randomly from soils of maize and peanuts fields in seven agro-ecological zones and characterized using morphological and physiological examination. Aspergillus section Flavi was detected in all the 57 soil samples collected in Kenya. Members of Aspergillus section Flavi L strain was the most common (54 %), followed by S-strains (35 %). Among Aspergillus, A. flavus was the most predominant (63.2 %), followed by A. parasiticus (27.7 %), A. tamari (5.5 %) and A. nomius (2.7 %). The mean CFU of the Aspergillus colonies per gram of soil was highly variable among the districts, ranging from 3.0 × 103 to 1.72 × 106 (p 0.05). The results also showed that A. flavus was detected in all the zones examined. Each of the regions had atoxigenic strains of potential value which can be employed as biological control agents in the management of aflatoxicoses.
Highlights
Grains of important food and export crops in Africa are susceptible to contamination by toxin-producing moulds
Distribution of Aspergillus section Flavi in Kenya Aspergillus section Flavi was detected in all the soil samples from 57 fields situated within the agro-ecological zones (AEZ) studied
A total of 220 section Flavi colonies were successfully transferred from Modified Rose Bengal Agar (MRBA) to 5/2 agar and subsequently identified by macroscopic, microscopic and growth characteristics in Aspergillus flavus and Aspergillus parasiticus agar (AFPA) medium
Summary
Grains of important food and export crops in Africa are susceptible to contamination by toxin-producing moulds. Aflatoxins are mycotoxins associated with liver damage and cancer in humans and animals These toxic substances are produced by fungi (such as Aspergillus flavus and Aspergillus parasiticus) in food and feed exposed to poor conditions during crop cultivation, storage or processing of harvest. The objective of this study was to isolate, identify and characterize atoxigenic and toxigenic strains of A. flavus and A. parasiticus in Kenya, and investigate possible application of atoxigenic strains in control of aflatoxin levels in maize and peanuts. Fungal communities in soils of maize and peanut fields were examined to determine the distributions of aflatoxin-producing Aspergillus species and to identify endemic atoxigenic strains. Grains of important food and export crops in Africa, such as maize and peanuts, are susceptible to contamination with different toxin-producing moulds. The major challenge is that the contaminated cereals such as maize may appear just like normal grains without any outward physical signs of fungal infection [7]
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