The effects of atoxigenic A. flavus co-applied with T. asperellum on the population dynamics of toxigenic A. flavus in the soil

Abstract

Aspergillus flavus is an important aflatoxigenic fungal specie infecting crops from production to storage. Contamination of foods and their products by these mycotoxins has become a problem worldwide; in Tanzania, related deaths were reported in 2017. This study focused on assessing the effectiveness of atoxigenic Aspergillus flavus, Trichoderma asperellum and a co-inoculated atoxigenic A.flavus and T.asperellum on the population dynamic of toxigenic A.flavus in the soil. A pot experiment was set in the screen house where a known concentration of fungal inoculum was added to the sterile soil. Aspergillus spp. were isolated from soil samples by dilution plate techniques on Modified Dichloran Rose Bengal (MDRB) agar and sub-cultured on potato dextrose agar (PDA). Identification was made using morphological and microscopic characteristics of culture in PDA media. Total colony forming units (CFU g^-1 of soil) and incidence percent were derived from colony count data recorded. R-statistical software version 4.0.4 was used to analyse the collected data. There was a significant difference between treatments on reducing the population (CFU/g) of toxigenic A.flavus in soil (p< 2.2×10^-16). Co-inoculated T.asperellum and atoxigenic A.flavus significantly reduced the population (CFU g^-1 of soil) of toxigenic A.flavus to 1.4×10⁵ CFU g^-1 of soil as compared to control treatment 4.5×10⁵ CFU g^-1 of soil. There was a strong positive correlation (p<0.001) between the incidence percent and population of toxigenic A.flavus in the soil under different biocontrol treatments. Co-inoculated T. asperellum and atoxigenic A. flavus had the lowest incidence of 36.3% to other treatments. The findings of this study demonstrate that co-inoculated atoxigenic A.flavus and T.asperellum was effective biocontrol treatment for reducing the population of Aspergillus flavus in the soil ecosystem.