Please describe your work
developing GMO potatoes and your position at Simplot.
Caius Rommens: I left my position as team leader
Monsanto to start an independent biotech effort at Simplot.
During the 12 years I worked there, I designed a
modified potato that I believed was resistant to bruise and late
blight, and that could be used to produce French fries that were
less colored and less carcinogenic than normal fries.
The main genetic
engineering of the Simplot GMO potatoes as described in your
book was silencing genes called RNAi.
What are some of the
possible negative consequences of silencing genes?
CR: Silencing is not gene-specific.
Any gene with a
similar structure to the silencing construct may be silenced as
well. It is even possible that the silencing that takes place
inside the GM potatoes affects the genes of animals eating these
I am most concerned about bees that don't eat GM
potatoes but may use GM potato pollen to feed their larvae.
Based on my assessment of the literature, it appears that the
silencing constructs are active in pollen.
You say that silencing the
PPO (polyphenol oxidase, a gene responsible for browning in
potatoes) gene increases toxins that accumulate in the GMO
Why are these toxins produced and what effects could
these toxins produce on human health?
CR: Ex-colleagues of mine had shown that PPO-silencing increases
the levels of alpha-aminoadipate by about six-fold.
is a neurotoxin, and it can also react with sugars to produce
advanced glycoxidation products implicated in a variety of
Monsanto GM corn variety, LY038, was found to have high
concentrations of alpha-aminoadipate, and an application for its
approval in Europe in 2009 was withdrawn after regulators raised
There is no data on the actual levels of alpha-aminoadipate in
GM potatoes, but I believe that Simplot should carefully
determine these levels.
Similarly, ex-colleagues had shown that the damaged and bruised
tissues of potatoes may accumulate high levels of
Such damaged tissues are normally identified and
trimmed, but they are concealed, or partially concealed, and
much of it is not trimmed in GM potatoes.
Therefore, it seems
important that Simplot should determine the full spectrum of
possible tyramine levels in their GM potatoes.
Another potential toxin is chaconine-malonyl. There is little
known about this compound, but ex-colleagues had shown that it
is increased by almost 200 percent upon PPO-silencing.
should probably be investigated.
In your book you write
that the GMO potatoes don't eliminate bruising but just conceal
it. Please explain.
CR: PPO-silencing prevents the darkening of bruises.
suppression of symptoms is so effective that we believed we had
overcome the bruise issue. It took me a lot of time to
understand that GM potatoes still have bruises - invisible
bruises - that are just as damaged as the darkening bruises of
In other words, the invisible bruises still are
entry points for pathogens and exit points for water, which are
two important issues during storage.
In addition to the claim
of eliminating bruises, Simplot says the Innate potato provides
"protection against late blight pathogen," and "reduced
asparagine, which contributes to reduced acrylamide in cooked
What are your reactions to these claims?
CR: The GM potato does contain a resistance gene that provides
protection against late blight.
The problem is that nobody knows
how long the protection will last. Plant breeders have tested
many different resistance genes in the past, and these genes are
almost always overcome by quickly evolving pathogens.
Another issue is that late blight is usually accompanied by
other pathogens. In humid regions of the world where late blight
is most active, there are dozens of other pathogens.
GM potatoes with a single resistance gene in, for example,
Bangladesh is like getting vaccinated for one tropical disease
and then moving to the tropics where there are many other
Next, the reduced
asparagine levels do lower the amount of
acrylamide in French fries, but these levels are already very
low in normal fries.
Simplot argues that the reduced acrylamide
levels reduce carcinogenicity, but I could not find any reliable
studies demonstrating that normal fries are carcinogenic.
The title of your book is
Pandora's Potatoes. What led you to choose this title?
CR: During the five years after my departure from Simplot, I
realized that I had not been rigorous enough in considering the
possibility that my modifications might have caused unintended
I then studied the publicly available literature that
was relevant to my past work, and identified a number of issues
that had been hidden from my view.
My GM potatoes had "hidden"
issues - like Pandora's Box.
What do you think should
be done with these GMO potatoes?
CR: I believe that, for the short term, GM potatoes entering the
consumer market should be evaluated for the incidence of hidden
bruise and infections and the range in levels of toxins such as
alpha-aminoadipate and tyramine.
Do you think the problems
you experienced in GMO potatoes will be similar in other GMO
CR: It is my experience that genetic engineers are biased and
narrow-minded. They may not be able to critically assess their
What is your perspective
on genetic engineering now after your work with the GMO potato
and misgivings about it?
CR: My concern about genetic engineering is that the absence of
unintentional effects can never be guaranteed.
It may take
dozens of years before these effects reveal themselves, and we
should be extremely cautious applying the technology.
What is your perspective
on CRISPR/gene editing?
CR: The problem with
CRISPR is that it changes the function of a
gene in all tissues of an organism.
This is a very important
limitation, because gene changes are mostly "useful" only if
implemented in a single tissue.
CRISPR has the same problems as genetic engineering.
In my book,
I explain that it requires manipulations in tissue culture that
These mutations have a negative effect on crop
performance and cannot be removed from certain crops including
apple and potato.
What do you see as the
best alternatives to GMO or conventional mono-cropped potatoes?
CR: Genetic engineering is meant to increase crop uniformity.
believe the opposite approach - to increase crop diversity -
will be more effective in increasing the sustainability of
I am most hopeful in the efforts of small companies such as
Solynta (A Dutch company that has developed an innovative non-GMO
technology for targeted breeding of potatoes).
The main benefit
of Soylnta's approach is that it breeds potatoes that have a
simpler genetic structure than cultivated potatoes - more like
that of wild potatoes - so that genetic traits can be combined
much more effectively.