Pathogenicity of fumonisin-producing and nonproducing strains of Aspergillus species in section Nigri to maize ears and seedlings

Authors: MUNKVOLD, GARY - Iowa State University; WELENETH, LAURA - Iowa State University; Proctor, Robert; Busman, Mark; BLANDINO, MASSIMA - National Research Council - Italy; SUSCA, ANTONIA - National Research Council - Italy; LOGRIECO, ANTONIO - National Research Council - Italy; MORETTI, ANTONIO - National Research Council - Italy

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2017
Publication Date: 2/1/2018
Citation: Munkvold, G.P., Weieneth, L., Proctor, R.H., Busman, M., Blandino, M., Susca, A., Logrieco, A., Moretti, A. 2018. Pathogenicity of fumonisin-producing and nonproducing strains of Aspergillus species in section Nigri to maize ears and seedlings. Plant Disease. 102(2):282-291. https://doi.org/10.1094/PDIS-01-17-0103-RE.
DOI: https://doi.org/10.1094/PDIS-01-17-0103-RE

Interpretive Summary: Fumonisins are toxins produced by certain fungi and are common contaminants in some crops, particularly corn. The toxins are of concern to food safety because of correlations between consumption of fumonisin-contaminated corn and esophageal cancer or neural tube defects in in some human populations for which corn is a dietary staple. The toxins can also cause multiple animal diseases, including cancer in rodents. Fumonisin contamination in corn has been attributed to fumonisin-producing species of the fungus Fusarium. Recently, it was discovered that some strains of some species of the fungus Aspergillus can also produce fumonisins, and these species also occur on corn. This discovery has led to the question: does Aspergillus contribute to fumonisin contamination in corn? The goal of the current study was to determine whether fumonisin-producing species of Aspergillus can cause disease on corn and contaminate corn kernels with fumonisins. Some of the Aspergillus strains examined were able to cause disease in corn ears and seedlings, but the levels of disease were not correlated with ability to produce fumonisins. Fumonisin contamination was detected in corn kernels that had been infected with fumonisin-producing strains of Aspergillus; however, the levels of contamination were low compared to levels resulting from infection with Fusarium. These results indicate that fumonisin contamination of corn caused by Aspergillus is not as significant as contamination caused by Fusarium. This information will be of use to academic, government, and private sector organizations working to assess the risk that fungi pose to food and feed safety as well as agricultural production.

Technical Abstract: Species of Aspergillus section Nigri are commonly associated with maize kernels, and some strains can produce fumonisin mycotoxins. However, there is little information about the extent to which these fungi contribute to fumonisin contamination in grain, the damage they cause to maize ears, or their effects on maize seed germination and seedling health. We compared fumonisin-producing and nonproducing strains of A. niger, A. welwitschiae, A. phoenicis, A. tubingensis, and A. carbonarius from the United States and Italy in laboratory and field studies to assess their ability to contribute to fumonisin contamination, to cause maize ear rot, 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 nonproducing 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. Contamination of grain with fumonisins was not consistently increased by inoculation with Aspergillus strains compared with the control, and was much greater in F. verticillioides-inoculated treatments than in Aspergillus-inoculated treatments. However, the ratio of the FB analogs FB2 and FB1 was altered by inoculation with some Aspergillus strains, indicating that FB2 production by Aspergillus strains occurred 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 caused by Aspergillus spp. is not as significant as that caused by Fusarium spp.