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Maysin Corn on Tap To Sour Pests Appetite?By Jan Suszkiw
October 24, 2000
Corn earworms could soon find themselves biting off more than they can chew. Agricultural Research Service scientists in Tifton, Ga., have developed four lines of inbred sweet corn whose silks have a natural compound called maysin that can kill this caterpillar pest.
Commercial crops of maysin-producing corn--still a few years off--could help farmers scale back their use of insecticides. In Florida, for example, sweet corn growers sometimes spray up to 40 times per season to ensure the unblemished, worm-free ears that consumers require. Nationwide, earworms cause $100 million in yield losses and increased insecticide costs. And spraying, while effective, can endanger beneficial insects.
The maysin in the new lines, on the other hand, is a natural defense restricted to corn silks, where earworms start their feeding, said team leader Neil Widstrom, with ARS Crop Genetics and Breeding Research Unit. Maysin also is only active in the earworms gut and isnt toxic to humans and other animals.
In forced-feeding trials, a maysin concentration of less than one third of 1 percent of the silk's total fresh weight was enough to kill 50 percent of earworms that digested it. In small- scale field trials this past summer, that sensitivity translated to very little ear damage in the maysin corn, versus a non-maysin control group that was not treated with insecticides.
Widstrom's team transferred the maysin trait into the sweet corn lines by crossing them with a southern dent corn. They then back-crossed the lines to the original sweet corn parent plant whose silks carry the trait. They also selected plants with tight husks, which forces earworms to chew on the silks before reaching the kernels.
Widstroms team is now using a genetic approach called marker-assisted selection to speed development of high-maysin hybrids. Their work is part of a cooperative research and development agreement that Novartis Seeds, Inc., renewed with ARS in August.
ARS is the U.S. Department of Agricultures chief research agency.