Identification of atoxigenic Aspergillus flavus from stored grains in controlling aflatoxin contamination in maize

Aflatoxins are carcinogenic fungal metabolites produced by several Aspergillus species, and current mitigation approaches offer no long-term solution. This study isolated and identified atoxigenic A. flavus from fifteen maize-growing areas in Bangladesh and evaluated their efficacy in limiting aflatoxin contamination in vitro and in planta . A total of 44 A. flavus isolates were identified by morphological characteristics and internal transcribed spacer (ITS) sequencing, and atoxigenicity was confirmed by amplification of nor1, aflR , and omtA genes of the aflatoxin biosynthesis gene cluster. In vitro , 38 isolates significantly (p < 0.01) reduced aflatoxin accumulation by 7% to 92.35% in inoculated maize grains, while 6 isolates increased accumulation by 2.73% to 49.16%. Isolates AF72, AF73, and AF76 increased aflatoxin accumulation despite being confirmed atoxigenic, whereas AF153, AF11, AF13, AF191, and AF90 reduced accumulation despite being confirmed toxigenic. In planta, all isolates significantly (p < 0.01) reduced aflatoxin accumulation by 80% to 90% except AF01 and AF165; notably, AF72 and AF73, which increased aflatoxin in vitro, reduced it in planta. Further research using cluster amplification pattern (CAP) analysis and single sequence repeat (SSR) genotyping is needed to confirm partial or complete deletion of genes in the aflatoxin biosynthesis gene cluster before these atoxigenic Aspergillus isolates can be declared suitable for biocontrol product development.