Exploring the Characteristics of Atoxigenic Aspergillus flavus Isolates and Their Biocontrol Impact on Soil Fungal...

Aspergillus flavus can produce aflatoxins, posing a threat of contamination to peanuts. To mitigate this issue, the use of biocontrol isolates, which do not produce aflatoxins (AF^-), has been considered to reduce aflatoxin levels. In this study, we evaluated five different AF^- isolates belonging to different vegetative compatibility groups, all of which exhibited varying degrees of deletion in aflatoxin biosynthesis gene clusters. One isolate that exhibited poor competitive ability against toxigenic A. flavus was eliminated, and the remaining four isolates were formulated as biocontrol agents and applied to a peanut field in Tai'an, Shandong, as a combination. Three months after application, the soil aflatoxin content was reduced from 0.62 ± 0.01 to 0.19 ± 0.03 μg/kg (inhibition rate: 69.35%). Among filamentous fungi in the soil, the proportion of AF^- isolates increased from 0% to 4.33%. Using SSR-specific primers, the microbial agents were recovered. We discovered that among the four AF^- isolates, CA04 had a lower colonization rate compared to the other three (only 12.00% of the total AF^- population), suggesting that the absence of sclerotia may result in poor reversibility and weaker dispersal ability. We utilized Illumina sequencing to investigate the changes in soil fungal ecology. The results showed a reduction in the population density of harmful fungi, such as Fusarium spp. (66.18%) and Plectosphaerella spp. (79.90%), but an increase in the density of Nothopassalora personata. This is the first study on the dispersal distance and soil fungal community structure following the application of AF^- agents in peanut fields in China.