Pathogenicity of fumonisin-producing and nonproducing strains of aspergillus species in section nigri to maize ears and seedlings

Species of Aspergillus in section Nigri are commonly associated with maize kernels and some strains in this group have the capacity for producing fumonisin mycotoxins, but there is little information about the damage they cause to maize ears, fumonisin (FB) contamination of grain, or their effects on maize seed germination and seedling health. We compared fumonisin-producing and non-producing strains of A. niger, A. welwitschiae, A. phoenicis, A. tubingensis, and A. carbonarius from the U.S. and Italy in laboratory and field studies to assess their ability to cause maize ear rot, to contribute to FB contamination, and to affect seed germination and seedling growth. In laboratory experiments, some strains of each Aspergillus species reduced germination or seedling growth, but there was high variability among strains within species. There were no consistent differences between fumonisin-producing and non-producing strains. In field studies in Iowa and Illinois, strains were variable in their ability to cause ear rot symptoms, but this was independent of the ability of the Aspergillus strains to produce fumonisins. FB contamination of grain was not consistently increased by inoculation with Aspergillus strains compared to the control, and was much higher in F. verticillioides-inoculated treatments than in Aspergillus-inoculated treatments. The ratio of FB2 to FB1 was altered by inoculation by some Aspergillus strains, indicating that FB2 production by Aspergillus strains was occurring in the field. These results demonstrate the pathogenic capabilities of strains of Aspergillus in section Nigri but suggest that their effects on maize ears and seedlings are not related to their ability to produce fumonisins, and that fumonisin contamination of grain by Aspergillus is not a major issue in comparison to that caused by Fusarium spp.