Submitted to: Mississippi Agricultural and Forestry Experiment Station Research Report
Publication Type: Experiment Station
Publication Acceptance Date: February 1, 1999
Publication Date: N/A
Interpretive Summary: Aflatoxin is a naturally occurring toxin produced by the fungus Aspergillus flavus in corn grain. The U.S. Food and Drug Administration limits the sale of grain with aflatoxin levels exceeding 20 ppb. The most desirable method of control is host plant resistance to fungal infection and subsequent aflatoxin accumulation. Unfortunately, no commercial hybrids have been identified with resistance, and very little information is available on the reaction of commercial hybrids to the fungus under field conditions. In 1998, we evaluated forty-five commercial hybrids for aflatoxin accumulation when developing ears were artificially inoculated with the fungus in the field. In one test, hybrids were inoculated by spraying fungal spores on the silks, and in another test, fungal spores were injected under the husks. Aflatoxin levels were extremely high regardless of inoculation method. When averaged across inoculation methods aflatoxin accumulation ranged from 890 to 10,018 ppb. Commercial hybrids with the Bacillus thuringiensis (Bt) toxin also had high levels of aflatoxin accumulation. Resistant hybrids from our research program had the lowest levels of aflatoxin. The resistant hybrid, Mp313E x Mp494, had the lowest level of aflatoxin contamination (110 ppb). These studies demonstrate the need for the development of aflatoxin resistant corn.
Technical Abstract: Commercial corn hybrids included in the 1997 Mississippi Agricultural and Forestry Experiment Station Variety Trials were evaluated for aflatoxin resistance at Mississippi State, Mississippi, in two separate field tests. In Test 1, hybrids were inoculated with Aspergillus flavus by injecting the spores under the husks. In Test 2, hybrids were inoculated with A. flavus by spraying the silks weekly for five weeks. At harvest, grain was dried, shelled, and mixed before determining aflatoxin contamination using the Vicam Aflatest. Alfatoxin levels were extremely high due in part to the severe environmental conditions experienced during the 1998 growing season. Similar levels of aflatoxin contamination were observed in both tests. Aflatoxin contamination of the commercial hybrids in Test 1 ranged from 529 to 11,936 ppb. In Test 2, aflatoxin levels ranged from 910 to 8,100 ppb. Two commercial hybrids with the Bacillus thuringiensis toxin were included in both tests and had high levels of aflatoxin contamination. Resistant hybrids that had Mp313E as one parent had the lowest aflatoxin levels in both the tests. The results of our tests demonstrate the need for development of aflatoxin resistant corn.