Pest-Resistant Potato on Tap
By Jan Suszkiw
April 17, 2009
A new russet potato germplasm line
developed by Agricultural Research
Service (ARS) scientists and collaborators could help cut the cost of using
chemical fumigants to fight Columbia root-knot nematodes (CRN).
The wormlike pests are problematic in the Pacific Northwest, where
two-thirds of America's potatoes are grown, as well as in Florida. Although
fumigating the soil before planting time diminishes the pest's numbers, the
practice isn't cheap, with some chemicals costing $300 per acre. Beneficial,
soil-dwelling insects can also be harmed, according to geneticist
Brown, with the
Vegetable and Forage Crops Research Unit in Prosser, Wash.
Thanks to genetic resistance, the new russet potato, PA99N82-4, offers a way
to naturally protect the roots and tubers against nematode feeding. Putting
that resistance to work hasn't been easy, though.
Brown and colleagues conducted painstaking screening of material from
Solanum bulbocastanum and other wild species kept at the
ARS U.S. Potato Genebank
in Sturgeon Bay, Wis. Because wild and cultivated potatoes are chromosomally
incompatible, the researchers resorted to bridging, a technique that fused
S. bulbocastanum and domesticated potato cells together, which forced
the DNA of both to combine. The cells were then stimulated to become plantlets.
Later, "backcrossing" was used to eliminate unwanted traits (like
tiny tubers and poor taste) from CRN-resistant plants that the researchers had
They also used DNA marker technology to identify plants harboring the S.
bulbocastanum gene for resistance, namely RMc1(blb). Normally, resistance
levels are determined by inoculating potted plants with nematodes, waiting
seven weeks and removing and washing the roots so the pests' eggs can be
counted. Use of DNA marker streamlines this process and identifies resistant
plants in one day, according to Brown.
PA99N82-4 will undergo two more years of field-testing before it is released
for use in developing commercial varieties.
more about the research in the April 2009 issue of Agricultural Research
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture.