April 2019 - 22

" What that meant was that nothing
of the wild material made tubers when
grown outdoors, " Tai said. " So you had
to take this wild material that had your
valuable resistance, cross it with the
domesticated species, and then grow
that material in a growth chamber
with short day lengths so you can get
the tubers, " she said. " And then you
have to backcross until you can select
away this short-day requirement for
tuberization. "
IDENTIFYING 'YUCKY' LEAVES
Today, Tai is still working to cross
varieties identified with resistance
with domestic varieties. " My job was to
develop a more efficient way to select
material, so the next one doesn't take 30
years, " Tai said.
What Tai found in the lab was
that the domesticated species were
producing material that beetles liked
to eat, and she wants to know why.
By looking at the leaf chemicals, she
was able to differentiate between what
she calls " yucky " leaves and " yummy "
leaves. Using their chemical profiles,
she was able to screen some of the
newer material to see if the chemicals
were present.
" In that way we would develop a
screening strategy for Colorado potato
beetle resistance without having to
put the plants in the field all the time,
and going through this long, laborious
process of scoring the amount of leaves
the beetles were eating, " she said.
Tai has since gone on to provide a
genetic map of these " yummy " and
" yucky " phytochemicals to determine
Get more
from
" The challenge was then to get this material
crossed with the domestic potato. The problem
with a lot of this wild material is that it doesn't
really make a lot of tubers. "
- Helen Tai, agriculture scientist, AAFC
which genes control their production.
The advantage of having this
information is that researchers are able
to use it as a DNA marker, which will
allow them to screen it along with other
markers in a single go.
AAFC recently released varieties
with Colorado potato beetle resistance.
They grow nice tubers and get decent
yields. Those varieties are currently
available for licensing. Mechanisms
for resistance can be stacked with
other mechanisms to create a stronger,
more viable plant. Different sources
of resistance are needed because the
genetically diverse Colorado potato
beetle adapts quickly, Tai said.
POSSIBLE TRAP CROPS
In the U.S., Zsofia Szendrei, associate
professor at Michigan State University,
has also conducted research on
Colorado potato beetle. She and her
colleagues looked at wild potato species
to see how the pest behaves on them.
" We have found interesting results
where the females lay eggs on a wild
species that was not suitable for the
larvae to feed on, " she said. " It was sort
of a dead end for them, and that was
really interesting.
" We tried to look for chemical features
of the plant that might explain why the
females are attracted, but the larvae are
not able to survive, but whatever we
looked at did not explain this unusual
response, " she said.
Understanding why females are
attracted to varieties that don't
provide feed for their young has its
advantages,
Szendrei
said,
pointing
out that there's potential to use those
varieties as trap crops.
" We set up a choice test in this
experiment where the cultivated potato
and the wild potato species were present
at the same time, and they chose this
wild potato species over the cultivated
potato, so you could technically try to
do this, " she said.
Limited funding meant that Szendrei
and her colleagues were not able to
conduct the choice test in the field, nor
was she able to continue the research.
She would still like to explore the
question more in the future, though,
as she believes the results have value
for U.S. potato growers.
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April 2019

Table of Contents for the Digital Edition of April 2019
