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 Novartisby 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
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.