Corn rootworm larva. Click the image for more
information about it.
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Corn Rootworm Population Studies: Faster,
Cheaperand Just As Good
By Ann Perry
May 19, 2008 Agricultural Research Service (ARS) scientists have led the way in finding
a new technique to obtain genetic markers to sort out corn rootworm
(Diabrotica virgifera) populations. This method is faster and cheaper
than existing techniques, and it can be used to characterize genetic variation
in any animal species.
Entomologists
Tom W.
Sappington and
Kyung
Seok Kim work at the ARS
Corn
Insects and Crop Genetics Research Unit in Ames, Iowa. For this research,
they partnered with ARS
North
Central Agricultural Research Laboratory entomologist
B. Wade
French in Brookings, S.D., and University of
Illinois colleagues Susan T. Ratcliffe and Lei Liu.
Researchers often use sections of DNA called short sequence repeats (SSRs)
to study the interactions between different populations of the same species.
Although they are superior genetic markers, SSRs are typically identified by
random, expensive and time-consuming searches through the total DNA extracted
from an individual organism.
However, SSRs are also found in sections of DNA called expressed sequence
tags (ESTs). Species-specific EST databases support genetic studies, including
the identification of SSRs, in a range of plants and animals.
The ARS team set out to resolve whether they could use SSRs obtained from
existing corn rootworm EST databasesnot SSRs identified from individual
DNAto study the genetic relationships of rootworm populations.
The researchers developed two sets of SSRs. One set contained 17 SSRs
developed using DNA from individual corn rootworms. The other set of 17 SSRs
was created from an existing database of 6,397 corn rootworm ESTs.
The scientists pitted the two sets in a head-to-head competition
characterizing five western corn rootworm populations from around the United
States and a Mexican corn rootworm population from Texas. They found that both
sets could be used to assign individuals to the correct populations with up to
80 percent accuracy.
These findings suggest that researchers studying population genetics can
save time and money by using ESTs in existing databases to identify SSRs,
instead of developing new SSRs from scratch.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.