New Peanut Types Could Mean Trouble for
By Jan Suszkiw
April 27, 1999
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 USDAs
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
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, Holbrooks 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
A more detailed story in Agricultural Research
magazines April issue is featured on the Web at:
ARS is the U.S. Department of Agricultures chief scientific arm.
Scientific contact: Corley Holbrook, ARS Nematodes, Weeds and Crops
Research Unit, Tifton, Ga., phone (912) 386-3372, fax (912) 386-3437,