Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2008
Publication Date: 4/17/2008
Citation: Poling, S.M., Wicklow, D.T., Rogers, K., Gloer, J. 2008. Acremonium zeae, a protective endophyte of maize, produces dihydroresorcylide and 7-hydroxydihydroresorcylides. Journal of Agricultural and Food Chemistry. 56(9):3006-3009. Available: http://pubs.acs.org/cgi-bin/abstract.cgi/jafcau/2008/56/i09/abs/jf073274f.html. Interpretive Summary: Acremonium zeae is characterized as a protective endophyte of maize that displays antifungal activity against fungal pathogens of maize. Pyrrocidines A and B were recently reported to be the metabolites accounting for this activity. During a population survey of A. zeae isolates from maize produced in several states, another metabolite of A. zeae, unrelated to the pyrrocidines, was found to have widespread occurrence and to be produced in amounts comparable to the pyrrocidines. Further chemical studies of this metabolite led to the identification of a new compound, dihydroresorcylide. Dihydroresorcylide was inactive against common fungal pathogens of maize, but caused a slight necrosis on maize leaves when applied to needle wounds. Dihydroresorcylide was detected in discolored maize kernels from ears that were wound-inoculated with A.zeae. While no specific biological activity can be attributed to dihydroresorcylide, its presence in maize kernels invites further study of the significance of this metabolite in endophyte-maize biology. The corn seed industry will benefit from the knowledge that A. zeae represents a potential confounding variable impacting the interpretation of results from disease resistance trials.
Technical Abstract: Acremonium zeae has been characterized as a protective endophyte of maize, and displays antifungal activity against other fungi. Pyrrocidines A and B were discovered to be the metabolites accounting for this activity. Pyrrocidine A has shown potent activity against major stalk and ear rot pathogens of maize. During a population survey of A. zeae isolates from maize seeds produced in nine states to determine their ability to produce pyrrocidines, another metabolite of A. zeae, unrelated to the pyrrocidines, was found to have widespread occurrence (105 of 154 isolates), and to be produced in amounts comparable to the pyrrocidines. Further chemical studies of fermentation extracts of an A. zeae isolate (NRRL 45893) from maize led to the identification of a new compound, dihydroresorcylide, the saturated analog of cis-resorcylide. Also identified were the two diastereomers of 7-hydroxydihydroresorcylide. Dihydroresorcylide caused necrosis on maize using the leaf-puncture wound assay (5 µg/needle wound) but was inactive (minimal inhibitory concentration > 50 µg/per milliliter) against common fungal pathogens of maize. Dihydroresorcylide and pyrrocidines A and B were detected by liquid chromatography-atmospheric pressure chemical ionization-mass spectroscopy in symptomatic maize kernels removed at harvest from ears of a commercial maize hybrid that were wound-inoculated in the milk stage with A. zeae NRRL 34559.