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On the horizon: two alternatives to transgenic corn

(March 22, 2001 -- Cropchoice news)-- American corn farmers who want to reduce their pesticide use and break away from transgenic crops may have a couple of options -- a natural compound that kills earworms and a Peruvian germ plasm that deters European corn borer.

Scientists at the Agricultural Research Service in Tifton, GA., have bred sweet corn whose stalks produce maysin, a natural compound that can kill earworms. Though commercialization of crops with maysin is a few years off, the hybrid could allow farmers to spray fewer pesticides. Earworms annually cause $100 million in yield losses.

Forced-feeding trials found that 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, which translated to little earworm damage in corn with the compound. Maysin remains in corn silks, where earworms begin feeding.

Meanwhile, in Mississippi, scientists have discovered a Peruvian germ plasm that naturally deters European corn borer. Were plant breeders to incorporate it into a viable corn hybrid, farmers could have a variety resistant to the borer, which damages $1 billion worth of U.S. corn annually, without relying on pesticides or transgenic varieties. Growers wouldn't have to deal with technology fees (as long as varieties with the resistant germ plasm are public), non-Bt corn buffers or elevators rejecting their corn because foreign markets don't want it.

The resistant germ plasm -- GEMS-0001 -- originated in northern Peru. Agricultural Research Service scientist Craig Abel told Farm Industry News that indigenous farmers probably selected corn with the germ plasm because of its resistance to the sugarcane borer, which feeds on both corn and sugarcane. Because the sugarcane and European corn borers have similar feeding habits, cross-resistance between the two pests may have occurred.

Rather than killing the borers, the germ plasm contains a chemical that slows larval development. Corn borer larvae normally feed on leaf tissue before boring into the stalk. With the Peruvian germ plasm, few of them move into the stalk.

Of the 1,600 corn germ-plasm lines that Abel evaluated in 1991 and 1992, 11 had ECB resistance. USDA researchers bred the GEMS-0001 resistance into two public lines from Iowa State University. They've released GEMS-0001 for seed companies to use in their breeding programs. However, commercial corn with the germ plasm won't be available for several years, until scientists insert it into hybrids with no yield drag.

For more information about maysin, contact: Neil Widstrom, ARS Crop Genetics and Breeding Research Unit, Tifton, Ga., phone (912) 387-2341, fax (912) 387-2321, nwidstro@tifton.cpes.peachnet.edu.

For more information about the Peruvian GEMS-0001, contact: Craig Abel at the Southern Insect Management Research Unit, Dept. FIN, 141 Experiment Station Rd., Stoneville, MS 38776, 662/686-5248 or circle 211.

Source: Agricultural Research Service, Farm Industry News