Characterization of Aflatoxigenic and Nonaflatoxigenic Isolates of Aspergillus flavus by Cultural and Immunological Methods
Characterization of Aflatoxigenic and Nonaflatoxigenic Isolates of Aspergillus flavus by Cultural and Immunological Methods
Iftikhar Jan* and Sahib Alam
ABSTRACT
This study aimed to characterize different Aspergillus section Flavi isolates in search for nonaflatoxigenic strains for use as biocontrol agent. A total of 434 isolates of A. flavus were isolated from soil and stored maize grain samples collected from four agroecological zones (AEZ) i.e., AEZ-A, AEZ-B, AEZ-C and AEZ-D of Khyber Pakhtunkhwa (KP) province of Pakistan. The mycological analysis of the samples demonstrated that the highest population of Aspergillus section Flavi was existed in soil (n = 236) than in maize grain samples (n = 198). Across all the four zones, the highest population of Aspergillus section Flavi was observed in AEZ-C (n = 115) whereas the lowest population was found in AEZ-B (n= 99). The isolates of Aspergillus section Flavi were then characterized for their aflatoxigenicity and nonaflatoxigenicity by cultural (i.e., production of blue fluorescence, room temperature phosphorescence, ammonium hydroxide vapor induced color change and sclerotia production) and immunological methods i.e., enzyme linked immunosorbent assay (ELISA). All the four cultural methods successfully differentiated aflatoxigenic and nonaflatoxigenic isolates, however ammonium hydroxide vapor induced test was found to be the most efficient (80.29%) for segregation of the isolates. Among all isolates, thirty were screened for their total aflatoxin production in corn meal agar medium by using ELISA technique. The results showed that isolate AFS32 produced highest level of total aflatoxin (230.78 µg Kg-1) while isolates AFS5, AFS17, AFS25 and AFS33 produced no aflatoxin. These nonaflatoxigenic isolates were considered as isolates of interest and could be used as biocontrol agent in agricultural fields for prevention of pre-harvest aflatoxins production in different crops.
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