An official website of the United States government.
<p>1. Refine aflatoxin biocontrol technology for peanuts and develop an effective system for achieving biological control of aflatoxins in corn, an important crop grown in rotation with peanuts.</p>
<p>2. Determine characteristics of soil populations important for invasion of peanut seeds by aflatoxigenic fungi and evaluate the competitiveness of nontoxigenic biocontrol strains of A. flavus.</p>
<p>3. Determine the chemical barriers of peanut to fungal challenge, particularly challenge by A. flavus. Investigate the basis for greater resistance to A. flavus invasion and aflatoxin contamination possessed by certain peanut genotypes for possible exploitation in breeding programs.</p>
<p>4. Conduct the necessary laboratory and field trials required by the EPA to extend the use of Aflaguard to other crops susceptible to aflatoxin, such as corn.</p>
Approach: 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.
<P>
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.
<P>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.