Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2002
Publication Date: October 1, 2002
Interpretive Summary: Aflatoxin contamination is a major impediment to profitable corn production in the southern USA. Aflatoxin, which is produced by the fungus Aspergillus flavus, is a potent carcinogen. Its presence at levels above 20 parts per billion restricts grain from interstate commerce and greatly reduces the value of the grain. Drought, high temperatures, and insect damage have been linked to aflatoxin contamination. Growing corn hybrids with genetic resistance to aflatoxin is generally considered a highly desirable method for reducing aflatoxin contamination, and germplasm lines that exhibit resistance to aflatoxin contamination have been developed and released by USDA-ARS scientists at Mississippi State. This investigation was undertaken to compare crosses among aflatoxin- resistant and susceptible lines for aflatoxin contamination with and without infestation of ears with southwestern corn borer. When environmental conditions were not favorable for fungal growth and aflatoxin production, aflatoxin levels were low even with high levels of southwestern corn borer damage. When environmental conditions were favorable for aflatoxin production, crosses that sustained high levels of southwestern corn borer damage were also highly contaminated with aflatoxin. Crosses with an experimental line exhibited the lowest levels of aflatoxin and southwestern corn borer damage. Selecting for resistance to both southwestern corn borer and A. flavus/aflatoxin should provide the best protection from losses to aflatoxin contamination in corn.
Technical Abstract: Aflatoxin, produced by the fungus Aspergillus flavus Link: FR., is a potent carcinogen and its presence at levels exceeding 20 ng/g restricts corn, Zea mays L., from interstate commerce. Aflatoxin contamination is a major impediment to profitable corn production in the southern USA where drought, high temperatures, and insect damage exacerbate the problem. Plant resistance is widely considered a desirable method of reducing aflatoxin contamination, and corn germplasm lines with resistance to aflatoxin production have been developed. This investigation was undertaken to determine whether these lines when used in crosses exhibited resistance to southwestern corn borer, Diatraea grandiosella Dyar, and to assess the effects of southwestern corn borer feeding on aflatoxin accumulation in hybrids with varying degrees of resistance. When environmental conditions were conducive to aflatoxin production, southwestern corn borer feeding caused increased contamination. When environmental conditions were not favorable for aflatoxin production, aflatoxin contamination levels were low even with extensive insect damage to the ears. The aflatoxin-resistant germplasm lines differed in response to southwestern corn borer. One experimental line, Mp80:04, exhibited resistance to both southwestern corn borer damage and aflatoxin accumulation.