Start Date: Dec 15, 2010
End Date: Apr 11, 2012
Experiments to extend the shelf life of afla-guard(r) will be conducted by producing afla-guard(r) with a variety of oils covering a range of oxidative stabilities. Samples will be placed in long-term storage at 4 degrees, 23 degrees, 30 degrees, 37 degrees, and 44 degrees C and tested once a month to determine the survival and viability of conidia on the coated barley. A multi-year (at least three) study will be conducted to determine the possibility of achieving biological control of aflatoxin contamination of corn. The field tests will include two plantings (3-4 weeks apart) of four treatments in a randomized complete block design with eight replications. Corn will be ground in a Romer subsampling mill, and the quantity and toxigenicity of A. flavus in the corn will be determined. Aflatoxins will be quantified in the same samples. Native fungal populations in 20 different soils will be quantified and species will be identified either directly on the dilution plates or by subculturing to Czapek agar slants. Peanut seeds will be aseptically wounded and inoculated with 7.0 mg of soil paste using a small spatula. Forty seeds will be inoculated with each soil and incubated 14 d at 37 C. Twenty-four uninoculated wounded seeds will serve as controls in each experiment. A. flavus and A. parasiticus sporulating on seeds will be identified by subculturing to Czapek agar slants. In a related series of experiments, nontoxigenic biocontrol strains (conidial-color mutant A. parasiticus NRRL 21369 and a nitrate-nonutilizing mutant of A. flavus NRRL 21882) will be added to soils at different concentrations to examine their interactions with native aflatoxin-producing populations. Aflatoxin analyses of individual seeds will be performed by extracting overnight in methanol and quantifying with high performance liquid chromatography. A series of experiments will be conducted to 1) isolate, identify, and quantify chemicals produced in peanuts in response to fungal invasion; 2) characterize the chemical response of peanuts representing a range of pod/kernel maturity to fungal challenge; 3) characterize the chemical responses of peanuts representing a genotypic range of recognized differences in susceptibility to A. flavus invasion and aflatoxin contamination; 4) characterize peanut wax composition and evaluate different genotypes for peanut wax content and composition.