High-Maysin Corn Available for Breeding

Agricultural Research Service scientists are accepting seed requests for new corn populations whose silks deter caterpillar feeding with a natural repellant called maysin.

By crossing the maysin-rich corn with elite commercial lines, plant breeders can eventually provide farmers with hybrids that will fare better against lepidopteran pests like the corn earworm. Its caterpillar stage causes $100 million annually in yield losses and control costs.

"The high-maysin material available now includes two corn populations," says Neil W. Widstrom, a geneticist in ARS' Crop Genetics and Breeding Research Unit at Tifton, Georgia. "It will be most useful to sweet-corn breeders, since there's more concern about ear damage for that crop than for dent corn."

Registration of EPM6 (a purple-kerneled population) and SIM6 (a yellow-kerneled population) in the November-December 2001 issue of Crop Science concludes 23 years of maysin research by scientists at ARS laboratories in Berkeley, California; Columbia, Missouri; and Tifton, Georgia, in cooperation with the University of Georgia.

The Tifton group, led by Widstrom, also concluded a 5-year cooperative research and development agreement this summer with Syngenta Seeds, Inc.—formerly Novartis—by providing the company with four high-maysin inbred sweet-corn lines.

Through breeding and backcrossing, scientists took a two-pronged approach to curbing earworm damage: First, they selected plants whose silks produce enough maysin to stop the caterpillar from feeding after just a few bites. Second, they chose plants with tight husks that force the pest to chew the silks before the kernels, which don't contain maysin.

Maysin works by binding up certain proteins in the earworm's gut so that it cannot grow. But humans, other animals, and beneficial insects face no danger from maysin.

Currently, farmers battle earworms with chemical insecticides. In Florida, where half the nation's fresh-market sweet corn is grown, this can often mean spraying 30-40 times a season to ensure the blemish-free ears consumers desire.

But with high-maysin hybrids, scientists predict, insecticide use could be cut in half. Their optimism is rooted in laboratory and field trials showing higher earworm mortality rates and less ear damage in high-maysin corn than in nonmaysin corn.

The ARS effort in Tifton has demonstrated that transferring maysin to silks of elite inbred lines is feasible, says Widstrom, adding "we'll honor requests for breeder seed of the released high-maysin populations for at least 5 years." Samples are limited to 100 grams, or about 300 to 500 seeds per request.—By Jan Suszkiw, Agricultural Research Service Information Staff.

Neil W. Widstrom is in the USDA-ARS Crop Genetics and Breeding Research Unit, 2747 Davis Rd., Tifton, GA 31794; phone (229) 387-2341, fax (229) 387-2321.

"High-Maysin Corn Available for Breeding" was published in the May 2002 issue of Agricultural Research magazine.