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Postharvest Pathology and Mycotoxins

Pathogenesis in Aspergillus Ear Rot of Maize: Aflatoxin B₁ Levels in Grains Around Wound-Inoculation Sites. M. G. Smart, Fermentation Biochemistry Research Unit and Mycotoxin Research Unit, USDA-ARS, Northern Regional Research Center, 1815 North University Street, Peoria, IL 61604; O. L. Shotwell(2), and R. W. Caldwell(3). (2)Fermentation Biochemistry Research Unit and Mycotoxin Research Unit, USDA-ARS, Northern Regional Research Center, 1815 North University Street, Peoria, IL 61604; (3)Department of Plant Pathology, Russell Laboratories, 1620 Linden Drive, University of Wisconsin, Madison, WI 53706. Phytopathology 80:1283-1286. Accepted for publication 21 February 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/Phyto-80-1283.

Aflatoxin contamination of preharvest maize intermittently presents serious problems in grain storage and in animal health. To determine whether this mycotoxin can be translocated through the ear in the absence of hyphae, we harvested 21 grains from around each of 21 wound-inoculation sites of maize ears matured at 34/30 C (day/night). Individual grains were analyzed for aflatoxin by enzyme-linked immunosorbent assay. Maize spikelets are borne in pairs and, if aflatoxin is transported in the rachis, grains in a pair should have similar toxin levels, but nonpaired grains may or may not. Statistical treatment showed that no two grains chosen at random had different average toxin levels: there was no pattern discernible in toxin accumulation. Highly contaminated individual grains rarely had highly contaminated neighbors. Finally, of the 413 grains assayed, almost 80% either were aflatoxin-positive and showed signs of the fungus or were not aflatoxin-positive and had no signs of the fungus. Only 58 grains (14%) had detectable toxin levels without fungal signs. We conclude that long-distance transport of aflatoxin does not occur in infected ears independently of the hyphae.