New Corn Lines Ward off AflatoxinBy
Researchers are closing in on new corn lines whose kernels fend off
harmful fungi with potent natural defenses. Commercial development of
such resistant corn, possible within a few years, could help reduce
aflatoxin contamination of the crop.
Since 1991, Agricultural
Research Service scientists in New Orleans have been testing
corn lines from all over the world for kernel resistance to Aspergillus
flavus, the culprit behind aflatoxin. Aflatoxin contamination of
crops by A. flavus is a serious problem during droughts. The
fungus produces the toxin in corn seed as well as peanuts and cotton.
Aflatoxin is so potent that no crop with more than 20 parts per
billion can be sold for animal feed.
One promising corn line tested by ARS plant pathologist
and colleagues is dubbed GT-MAS:gk. The researchers discovered that
the lines kernels wear a thick, waxy coat that
inhibits the growth of A. flavus. Theyre also trying to
identify natural chemicals in the kernel wax that may foil the fungus.
Other resistant corn lines they examined have kernels with high
levels of a protein called a trypsin inhibitor that keeps A.
flavus and other fungi at bay. The New Orleans group and ARS
colleagues based at Mississippi State University are testing the
proteins insecticidal properties against corn earworms. Chewing
damage caused by this caterpillar pest helps virulent fungi gain
easier entry to the plant.
Key to the scientists research is a kernel screening assay for
measuring aflatoxin levels. It is fast and easy to use and requires
only a few kernels. When used with a fungus equipped with a genetic
fragment called a reporter gene, the assay allows researchers to
pinpoint the microbes locale or concentration on seeds. This
also helps reveal seed regions where resistant mechanisms might be at
work. Plant breeders will also find the assay useful.
Scientific contact: Robert Brown, ARS
and Feed Safety Research Unit,
Research Center, New Orleans, La., phone (504) 286-4359, fax
(504) 286-4419, Rbrown@nola.srrc.usda.gov.