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Aspergillus section Flavi species co-occur and contaminate crops, including maize and groundnuts, with aflatoxins. Competition among A. flavus genotypes is influenced by crop host, but competition between Aspergillus species has not been examined. Objectives of the current study were to 1) assess competition among four aflatoxin-producing species on maize and groundnuts, and 2) evaluate within-species variation in competitive ability during co-infection with another species on the two crops. For Objective 1, maize and groundnut kernels were co-inoculated with all possible pairs of A. flavus, A. parasiticus, A. aflatoxiformans, and an unnamed taxon known as the Lethal Aflatoxicosis Fungus (LAF). For Objective 2, three isolates from each of the four species were co-inoculated with a representative isolate of a competing species on the two hosts. In all experiments, isolates were co-cultured for 7 days at 30°C and then aflatoxins and total conidia were measured, and percentages of each species within a treatment were assessed with quantitative pyrosequencing. Maize kernels supported greater aflatoxin production than groundnuts while groundnuts supported greater sporulation than maize. Hosts differentially influenced competition between species with A. flavus generally more competitive on maize and LAF more competitive on groundnuts. Overall, A. flavus and LAF were the most competitive species while A. parasiticus was the least competitive. However, isolates within a species varied in competitive ability and in their response to host and competing species. Results suggest that though crop hosts influence Aspergillus community composition, within-species variability makes it difficult to predict outcomes of competition on a particular crop. |
