April 2019 - 26

PVYN-Wi
PVY Positive
PVY Negative
Yield (pounds per plant)
2.2
5.5
is down as well (although still second).
If you're looking at (finding) resistance,
then look at PVYN-Wi. "
The cultivars used in the studies
included Altura, Bannock Russet,
Clearwater Russet,
Ranger Russet,
Russet Burbank, Umatilla Russet,
Waneta and Yukon Gold. The nonrussets
proved to be especially
susceptible to the virus.
" One of the most susceptible is
Yukon Gold, " Karasev said. " Also
Waneta and Altura. "
Altura, especially, infected with N-Wi
tend to show symptoms once in
storage. Fifty-three percent of the
Alturas inoculated with N-Wi showed
symptoms while in storage, whereas
the
russet
varieties
held up much
better in storage.
" One of our recommendations is to
be very cautious if your Alturas have
Wilga, " said Olsen, who added that
Alturas from a Wilga-infected field
should probably be shipped as soon as
possible.
Among the russets, Burbank
showed
more
susceptibility
than
other varieties. During a screenhouse
inoculation study that focused on
NTN, N-Wi and O, the infection rate
was above 70 percent for Burbank
for all three strains - and nearly 95
percent for N-Wi - yet infection rates
were under 20 percent for for both
Bannock and Clearwater, and even
under 10 percent in multiple cases.
Burbanks actually held up better than
the other varieties of not developing
symptoms while in storage. Only 20
percent of Burbanks inoculated with
NTN showed symptoms and 14 percent
inoculated with O did. Olsen said it was
surprising to see how many potatoes
26
Spudman.com
Alturas Field Study 2017
Specific Gravity
1.0772
1.0850
Mean Fry Color
62.3
62.1
" It is really important to get those samples in
so you know what strain you're dealing with so
you can respond appropriately to that strain
and that variety. "
- Nora Olsen, professor, University of Idaho
infected with O showed symptoms in
storage. Ranger (100 percent), Altura
(70) and Umatilla (69) were at a much
higher rate than Burbank.
" We never really thought of O being
a strain that would provide symptoms,
but they can in certain circumstances, "
Olsen said.
Because of the variances between
the different strains and uneven effects
on different varieties, knowing which
strain is present can be key for growers.
" It is really important to get those
samples in so you know what strain
you're dealing with so you can respond
appropriately to that strain and that
variety, " Olsen said.
Studies also found that a higher
percentage of plants show symptoms
when the virus wasn't present at
planting than when it was. " That's
because seed-borne (infected) plants
tend to die off early, " Olsen said.
NEXT STEPS
No grower wants PVY in his or her
fields, but it commonly happens. When
it's present, the key, from a production
standpoint, is avoiding the show of
symptoms. The fallout from those
symptoms can go well beyond just the
virus itself.
" Symptoms, when they are there, can
impact fry color, but also they break
the skin of the potato often, " Olsen
said. " That becomes an entry point for
other diseases, whether it be soft rot
or anything else. ... So that's one of the
concerns we have on the symptoms,
not just the fry color or aesthetic, but
that they can be an entry point. "
Not surprisingly, research showed
stressed plants produce symptoms at
a much greater rate than non-stressed.
The biggest thing a grower can do is
maintain optimal plant health, Olsen
said.
" It's hard when you have, say 50
percent PVY out in that commercial
field, having to decide do you put more
nitrogen on it, " Olsen said. " We try to
recommend to just try to minimize
stress as much as possible in those
fields and carry on as best as you
possibly can. "
A portion of the Specialty Crop
Research Initiative, which is scheduled
to get underway this year, will focus
on management and control of tuber
necrotic and vector-borne viruses of
potato. That also will include breeding
research for resistance to PVY, as well
as potato mop-top virus (PMTV) and
tobacco rattle virus (TRV).
http://www.Spudman.com
April 2019

Table of Contents for the Digital Edition of April 2019
