February 2021 - 21

" common garden experiment, " where they grow potatoes
in small plots using soil that has never been exposed
to potatoes and soil that has been exposed to potatoes.
They plan to characterize the soil by quantifying all of the
microbes present in both soil types.
" We expect to see the potatoes grown in the
virgin soil perform better, " said Wheeler, who is the
principal investigator on the project. He is working
in collaboration with soil scientists and pathologists.
Using DNA sequence data, the aim is to identify fungi,
bacteria and nematodes present in the soil.
" We hope that the yields are higher and disease
intensity is lower, " he said. " If it does work, if we do see
that effect, then we'll try to reproduce it at scale by maybe
finding some of the microbes that are very associated
with the virgin soil and perhaps trying to inoculate them
into soils that are not virgin, for example. "
But the process is very complicated and there are
many factors that impact the disease.
Wheeler is also part of a project that is working to
identify the verticillium genes that are associated with
disease in potatoes, as well as infection in asymptomatic
crops like mustard.
" The reason why that might matter is that if we can
find genes that are associated with genes in potato,
we can give those data to breeders and they can help
develop resistance, " said Wheeler.
In the future, the hope is that geneticists are able
to convey resistance via RNA interference using geneediting
technology.
" The advantage of that would be that we wouldn't
have to apply fungicides if it worked, " said Wheeler.
" That would be awesome. But we have to convince
consumers that it's safe, and that's a very big hurdle. "
In the meantime, Steven Johnson, Extension Crops
Specialist, University of Maine, said the best course
of action is still prevention. Avoid introducing the
pathogen to uninfected fields, including via dirty
equipment, and use clean, high quality seed, he said.
For
those
farmers whose
fields
already
have
verticillium wilt, rotation is the best long-term
solution. The success of this management strategy was
particularly evident this past growing season when
most of Maine's potato farmers faced severe drought.
" When there's a drought, verticillium wilt comes
on faster, it's more exacerbated and a plant that could
probably handle a low level of verticillium and not
show a significant symptom shows it now because
the vascular system is so stressed it doesn't take much
plugging with the pathogen, " said Johnson.
" The people who had longer rotations... it was very
noticeable, " he added.
A three-year rotation is best, advised Johnson. And
while that wouldn't be long enough in other states,
Maine experiences long, cold winters, which helps
reduce pathogen load come spring.
" But the real bottom line here is that extended
rotation did show a lot of value, " Johnson concluded.
Spudman * February 2021
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February 2021

Table of Contents for the Digital Edition of February 2021
