<i>Aspergillus tamarii</i> and <i>A. flavus</i> Differentially Allocate Resources Between Mycelial Growth and Sporulation During Competition on Maize Kernels

Understanding the ecology of fungi in Aspergillus section Flavi is necessary to identify factors that contribute to aflatoxin accumulation risk and to improve interventions to reduce contamination. For example, interactions between non‑aflatoxigenic and aflatoxigenic Aspergillus species play a key role in determining the aflatoxin-producing potential of crop-associated fungi. The non-aflatoxigenic species A. tamarii is often associated with agricultural soils and occasionally with crops, prompting the question as to whether A. tamarii and aflatoxigenic A. flavus compete on these crops. In this study, interactions between A. tamarii and A. flavus during co-colonization and sporulation on maize kernels were assessed. In co-culture experiments, mycelial and conidial growth was measured for each species using a custom quantitative PCR assay, and aflatoxin was measured via lateral flow. Both A. tamarii and A. flavus exhibited reduced growth under co-culture, confirming these species compete for shared resources in maize kernels. However, their responses diverged in ways that suggest distinct life history strategies. In competition, there was a significant relationship between mycelial growth and production of conidia for A. tamarii. In contrast, for A. flavus isolates mycelial biomass in kernels and conidia production during co-colonization of maize kernels with A. tamarii were not correlated. This suggests differences in resource allocation between growth and reproduction between the two species. Additionally, isolate identity influenced competitive outcomes and aflatoxin production, underscoring the importance of genotype-level variation in fungal interactions. Understanding these species-specific interactions provides insight into fungal dynamics on crops and may inform strategies for managing aflatoxin contamination events.