Abstract
Aspergillus flavus refers to a diverse group of saprophytic soil fungi that includes strains producing aflatoxins (toxigenic strains) in the kernels of corn (Zea mays L.) and other crops, causing pre-harvest and post-harvest aflatoxin contamination. Some A. flavus strains are atoxigenic, and the introduction of such strains into the crop environment helps reduce toxigenic aflatoxin contamination. Corn growers in Texas have used the product FourSure™, which contains four atoxigenic strains of A. flavus; however, effects on soil microbial communities associated with these applications are unknown. We compared soil fungal and bacterial communities in corn fields treated with FourSure™ to nearby untreated (control) corn fields in Texas during the summer of 2019. Analysis of soil microbial community structure showed that total fatty acid methyl esters (FAMEs), fungal, and bacterial populations were not significantly different (p = 0.31) between the FourSure™-treated and control fields, yet corn fields located in the northern counties had more (p < 0.05) Gram—bacteria, actinobacteria, and total bacteria than fields in the southernmost county. The Gram—bacteria and actinobacteria were positively correlated (p = 0.04; r = 0.48 and 0.49, respectively) with soil water content. Similar fungal and bacterial abundances between FourSure™-treated and control fields indicated that atoxigenic A. flavus had no negative effects on soil microbial communities.
Highlights
IntroductionA saprophytic soil fungus, Aspergillus flavus, is a diverse species complex of soil fungi that includes strains producing aflatoxin (i.e., toxigenic strains) as well as strains that do not produce aflatoxin (i.e., atoxigenic strains)
A saprophytic soil fungus, Aspergillus flavus, is a diverse species complex of soil fungi that includes strains producing aflatoxin as well as strains that do not produce aflatoxin
While another recent study using the same corn fields reported a trend of lower abundances of soil-nesting native bees in A. flavus-treated corn fields than in control fields [14], we found similar abundances of soil microbial communities across A. flavus-treated and control fields, indicating that the soil microbial component was not affected by atoxigenic A. flavus (FourSureTM) applications
Summary
A saprophytic soil fungus, Aspergillus flavus, is a diverse species complex of soil fungi that includes strains producing aflatoxin (i.e., toxigenic strains) as well as strains that do not produce aflatoxin (i.e., atoxigenic strains). These fungi can cause aflatoxin contamination in the kernels of corn (Zea mays L.) [1], and seeds of cotton (Gossypium hirsutum L.) [2] and many other crops both before and after harvest [3]. Aspergillus flavus is an opportunistic pathogen and causes aspergillosis diseases in animals and humans, and is one of several species of Aspergillus that cause stonebrood in honey bee (Apis mellifera L.) [6]. Sclerotia germinate and form new conidial inoculum in a short period when they are exposed to the soil surface, usually in spring
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