Submitted to: Mycological Society of America
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2012
Publication Date: 4/24/2012
Citation: Horn, B.W., Sorensen, R.B., Lamb, M.C., Sobolev, V., Carbone, I. 2012. Formation of Aspergillus flavus sclerotia on corn grown under different drought stress conditions. Mycological Society of America. Interpretive Summary: None required.
Technical Abstract: Aspergillus flavus is a major producer of carcinogenic aflatoxins worldwide in corn, peanuts, tree nuts, cottonseed, spices and other crops. Many countries have strict limits on the amount of aflatoxins permitted in human commodities and animal feed. Sclerotia produced by A. flavus serve several functions in the life cycle of the fungus: (1) resistance to adverse environmental conditions; (2) colonization of substrates through myceliogenic and sporogenic germination; and (3) sexual reproduction. Drought stress in corn results in an increase in aflatoxin contamination, but little is known about the effects of drought on sclerotium production. Corn was grown at Shellman, Georgia, in 2010 under different drought stress conditions consisting of: rainfall only (0% irrigation) and 33, 66 and 100% of the recommended irrigation amounts. Decreasing water availability showed a progressive reduction in grain yield (r = 0.96, p < 0.001) and an increase in aflatoxin concentration (r = –0.62, p < 0.05), but had no significant effect on percentage of ears showing Aspergillus section Flavi sporulation or percentage of ears with sclerotia. Of the 8706 ears examined, sclerotia (n = 6022) were recovered from 84 ears (1%). Sclerotia of A. flavus L (large sclerotial) strain were dominant (78 ears); less common were sclerotia of A. flavus S (small sclerotial) strain (8 ears), A. parasiticus (3 ears) and A. alliaceus (2 ears). The sexual stage was not detected in any sclerotia, including those of homothallic A. alliaceus, suggesting that sclerotia may require additional incubation after dispersal onto soil.