STORY LEAD:
New Peanut Types Could Mean Trouble for Nematodes
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ARS News Service
Agricultural Research Service, USDA
April 27, 1999
Jan Suszkiw, (301) 504-1630, jsuszkiw@asrr.arsusda.gov
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New peanut strains from abroad could spell relief for southern peanut
farmers bedeviled by root-knot nematodes, tiny roundworms that cost $20-40
million annually in losses and chemical controls.
Geneticist Corley Holbrook of USDA's Agricultural Research Service worked
with ARS colleagues to examine hundreds of exotic peanut strains whose roots
deter the nematodes from feeding or laying their eggs. About two dozen of
the top picks are now being crossed with commercial cultivars to improve
their pest resistance, reports Holbrook, at ARS' Nematodes, Weeds and Crops
Research Unit.
Such cultivars could be available within five years, offering peanut farmers
in Georgia, South Carolina and other southeastern states a welcome respite
from chemical nematicides.
Female Meloidogyne arenaria nematodes are prime targets for such chemical
control. Unchecked, they establish knot-like feeding sites called root galls
on plant roots. These galls choke off nutrients needed by the peanut plant,
sometimes causing yield losses of more than 70 percent. Females also lay
thousands of eggs on the roots, setting the stage for more losses next
season.
To break the cycle, Holbrook's group examined peanut germplasm collected
from Asian, African and South American countries. They began with the
National Peanut Germplasm Collection in Griffin, Ga., where 7,000 seed
samples, called "accessions," are stored.
>From a core collection of 831 accessions, they narrowed the search to 36
resistant strains. Next followed a painstaking screening regimen in the
greenhouse. There, scientists repeatedly exposed the plants to the nematodes
to rate the severity of feeding and egg-laying.
Compared to commercial check varieties like Florunner, 21 of the peanut
strains suffered 70 percent fewer root galls and egg clusters. Two Chinese
peanuts showed a 90 percent reduction. Both are top picks for breeding new
domestic cultivars.
A more detailed story in Agricultural Research magazine's April issue is
featured on the Web at:
http://www.ars.usda.gov/is/AR/archive/apr99/pean0499.htm
ARS is the U.S. Department of Agriculture's chief scientific arm.
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Scientific contact: Corley Holbrook, ARS Nematodes, Weeds and Crops Research
Unit, Tifton, Ga., phone (912) 386-3372, fax (912) 386-3437,
holbrook@tifton.cpes.peachnet.educ.
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