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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Publications at this Location » Publication #429174
Research Project: Improvement of the Aflatoxin Biocontrol Technology Based on Aspergillus flavus Population Biology, Genetics, and Crop Management Practices

Location: Pest Management and Biocontrol Research

Title: Aspergillus tamarii and A. flavus differentially allocate resources between mycelial growth and sporulation during competition on maize kernels

Author
item BYRNE, ALLISON - Oak Ridge Institute For Science And Education (ORISE)
item Mehl, Hillary
item Callicott, Kenneth

Submitted to: PhytoFrontiers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2026
Publication Date: 3/17/2026
Citation: Byrne, A.Q., Mehl, H.L., Callicott, K.A. 2026. Aspergillus tamarii and A. flavus differentially allocate resources between mycelial growth and sporulation during competition on maize kernels. PhytoFrontiers. https://doi.org/10.1094/PHYTOFR-09-25-0094-R.
DOI: https://doi.org/10.1094/PHYTOFR-09-25-0094-R

Interpretive Summary: Contamination with aflatoxins, potent cancer-causing toxins produced by Aspergillus flavus and its close relatives, is a major food safety concern for crops including corn, peanuts, and tree nuts. Due to regulations that place limits on allowable levels throughout the value chain, aflatoxin contamination results in annual losses of hundreds of millions of dollars for US producers and processors. One effective approach for pre-harvest reduction of aflatoxin contamination is biocontrol with non-aflatoxin producing strains of A. flavus. However, the extent to which other crop-associated Aspergillus species can reduce the risk of aflatoxin contamination has not been well characterized, and they may be sources of additional modes of action for aflatoxin biocontrol. Aspergillus tamarii is a related fungus that does not produce aflatoxins and is often found in association with agricultural soils and crops. Thus, the current study examined interactions between different strains of A. tamarii and aflatoxin-producing A. flavus during infection of corn kernels. Aspergillus tamarii was able to suppress growth of A. flavus within kernels and during sporulation on kernel surfaces, but outcomes of competition between the two species were strain dependent. The two species differed in their allocation of biomass to vegetative growth (kernel colonization) versus reproduction (sporulation) during co-infection of corn suggesting A. tamarii and A. flavus utilize different strategies during competition. Aspergillus tamarii strains with superior ability to outcompete A. flavus were identified, and these may be useful as active ingredients in multi-species biocontrol formulations for mitigation of aflatoxins in crops.

Technical Abstract: 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 fungal dominance and the overall aflatoxin-producing potential of the fungi associated with crops and the fields in which they are grown. 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. 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 quantities of conidia produced 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 strongly influenced competitive outcomes, particularly for mycelial growth, underscoring the importance of genotype-level variation in fungal interactions. Understanding these species-specific interactions provides insight into fungal dynamics on crop substrates and may inform strategies for managing aflatoxin contamination events.