MaysinA Natural Insecticide from
A natural insecticide in the silk of some corn lines will deter earworms in the
future if ARS scientists succeed in transferring genes that control the
production of maysin.
The worm that turns the sweet corn ear into mush may be in for a turn of
events, thanks to a plan as smooth as silkcorn silk, that is.
Agricultural Research Service
scientists at Columbia,
Georgia, plan to manipulate a genetic pathway in corn silks to boost the
production of maysin, a compound that gives the plant natural insect
"If it works, it will mean a sweet success for consumers and
growers," says Michael McMullen, an ARS
plant geneticist. "An added benefit of controlling the corn earworm would
be in keeping it from moving on and damaging other crops like alfalfa, cotton,
peanuts, and tomatoes."
Earworms cost U.S. growers more than $100 million annually. Increasing
maysin concentrations in corn silks could reduce insecticide used on sweet corn
by up to 85 percent. Commercial growers sometimes have to apply insecticides 30
times a season to keep earworms out of sweet corn.
Adult earworms lay their eggs directly on the silk of growing corn, where
the larvae hatch about 3 days later. The newly hatched larvae eat their way
through the silk, then feed on kernels, before dropping to the soil to mature.
After 12 days, new adults emerge from the soil and fly away in search of
fresh food. It's then that they move into all sorts of other crops, including
many home gardens.
The research plan, as designed by McMullen and plant geneticist Patrick
Byrne, is to locate and characterize the genes that regulate the
McMullen and Byrne are working with plant geneticist
Wiseman, and University of Georgia chemist Maurice Snook.
They have already identified a gene named P1 that regulates more than
half the amount of maysin in one corn population. If they can increase the
expression of P1 in corn silks and identify and manipulate other pathway
genes, they then can increase the amount of maysin.
"Maysin, which occurs mainly in corn silk, binds up amino acids in the
earworm's gut so the insect can't use them and literally starves to
death," says Byrne.
Once the Missouri group has identified the key maysin genes, Widstrom will
cross and select corn plants in Georgia that have the desired genetic makeup.
Maysin was first identified as a compound conferring resistance by the
Tifton scientists in 1979. But only recently have gene mapping techniques
become advanced enough that the likelihood of built-in resistance to earworms
is just a few years away.
The Tifton researchers found maysin in a primitive race of corn from Mexico,
highlighting the value of maintaining a large collection of exotic stocks in
USDA's National Plant Germplasm
System. By Linda Cooke, ARS
McMullen is in the USDA-ARS Plant Genetics Research Unit, University of
Missouri, 204 Curtis Hall, Columbia, MO65211; phone (573) 882-7606.