Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2008
Publication Date: July 30, 2008
Citation: Wicklow, D.T., Pearson, T.C., Brabec, D.L. 2008. Evaluation of intraspecific competition (Aspergillus flavus Link) and aflatoxin formation in suspended disc culture and preharvest maize. Meeting Abstract. Technical Abstract: The abilities of non-aflatoxin producing strains of Aspergillus flavus NRRL 32354; 18543; 21882; 21368 as well as domesticated koji strains Aspergillus oryzae (syn. A. flavus var. oryzae) NRRL 451; 1911; 5592; 6271; 30038 to interfere with aflatoxin formation by A. flavus NRRL 3357; 32355 were examined in suspended disc culture (SDC) and by wound-inoculating maize ears in the late milk to early dough stage of maturity at Kilbourne, Illinois, in 2001 and 2002. In SDC aflatoxin yields were substantially reduced when conidia were mixed in equal proportions at a constant total density 1x 105 spores /ml-1. Non-aflatoxin producing strains of A. flavus reduced aflatoxin yields in NRRL 3357 by an average of 70% and NRRL 32355 by an average of 95%, while strains of A. oryzae reduced aflatoxin yields by an average of 62% & 73%. In pre-harvest maize (2001 & 2002) non-aflatoxin producing strains of A. flavus reduced aflatoxin levels in NRRL 3357 by an average of 63% & 79% but were largely ineffective in suppressing aflatoxin levels when paired with NRRL 32355 (red. 26% & incr. 41%). The parasitic ability of competing strains may be as important as intraspecific competition in determining the extent to which the seed becomes contaminated with aflatoxin. In both years, non-aflatoxin producing strains of A. oryzae supported substantially greater aflatoxin yields when paired with NRRL 32355 (incr. 70% & incr. 377%), which may be the result of nutritional cross-feeding. Aspergillus flavus populations in the central corn belt may include a majority of strains that produce no aflatoxin and thus could function naturally in suppressing the severity of aflatoxin outbreaks.