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Poster: Diseases of Plants: Crop Loss Assessment


Understanding fungal reservoirs: tracking Aspergillus populations in air, soil, crop debris and the reproductive organs of Bt and non-Bt corn
H. ABBAS (1), M. Weaver (1), C. Accinelli (2), W. Shier (3), R. Zablotowicz (1) (1) USDA-ARS, U.S.A.; (2) University of Bologna, Italy; (3) University of Minnesota, U.S.A.

Aspergillus flavus can colonize a wide range of environments. The advent of effective biocontrol agents makes it important to know where fungi overwinter, because the amount and toxigenicity in each reservoir may determine the most effective site(s) to apply biocontrol. Aspergillus propagules on leaf, husk, silk and tassel of Bt and non-Bt corn, and from soil and air/dust were quantified using dilution plating on dichloronitroaniline rose Bengal agar. There was no effect of Bt corn on the amount of Aspergillus propagules. Aspergillus propagules in air/dust varied dramatically from year to year (0-278 cfu/1000L). We studied corn hulls, cob and kernel fragments that accumulated near on-farm grain storage bins in normal farm operations and were periodically moved to the edge of an adjacent field and disked into soil in fall tillage. The following March, A. flavus propagules in soil samples ~20, ~30 and ~40 meters from the bins were 1,500-28,000 CFU/g, with ~3 times as many at 20m as at 40m, but 24% aflatoxigenic at all distances. In January 2016 similar debris and dust accumulating near on-farm grain storage bins contained 14,500±5,400 CFU/g A. flavus propagules. Additional studies on A. flavus propagules from rice, sesame and Illinois corn field soil and plant debris will be discussed. The findings are consistent with a substantial plant debris-associated soil populations. These findings are very useful in selecting optimal biological control strategies for aflatoxin.