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Poster: Biology & Disease Mgmt: Postharvest Pathology & Mycotoxins


Conidial versus sclerotial production: implications for corn and soil niche specialization in Aspergillus flavus
R. SWEANY (1), C. DeRobertis (1), K. Damann (1) (1) Louisiana State University Agricultural Center, U.S.A.

Aspergillus flavus contaminates corn and other oil-seed crops with carcinogenic aflatoxin. The populations of A. flavus differ between soils and crops. In Louisiana, native A. flavus isolated from soil and corn in 11 fields revealed only 6 of 16 vegetative compatibility groups (VCG) infected corn. During inoculum production for an infectivity titration experiment to verify niche specialization, two predominant VCGs in corn produced approximately 15 times more conidia than the most widespread soil VCG. Instead of producing conidia, the widespread soil VCG produced copious sclerotia. To test the hypotheses that corn infecting strains produce more conidia and soil inhabiting strains more sclerotia, three isolates from each of 16 VCGs were grown on Czapek Dox and Wickerham solid media and assessed for conidial or sclerotial production respectively. Generally corn VCGs produced more conidia; two VCGs comprising 91% of corn isolates produced significantly more conidia (3-60X) than 9 of 10 strictly soil VCGs. Conversely, those two corn VCGs produced very limited sclerotia, whereas all strictly soil VCGs produced significantly more sclerotia (10-100X). High conidial production appears to correlate with corn infection, whereas production of resting bodies appears to correlate with survival in the soil. Suppression of conidial production toward sclerotial production may reduce corn infection and limit outbreaks of aflatoxin contamination in corn.