Biotech Potatoes in the 21st Century: 20 Years Since the First Biotech Potato

Abstract

Potato is the world's most important vegetable crop, with nearly 400 million tons produced worldwide every year, lending to stability in food supply and socioeconomic impact. In general, potato is an intensively managed crop, requiring irrigation, fertilization, and frequent pesticide applications in order to obtain the highest yields possible. Important traits are easy to find in wild relatives of potato, but their introduction using traditional breeding can take 15–20 years. This is due to sexual incompatibility between some wild and cultivated species, a desire to remove undesirable wild species traits from adapted germplasm, and difficulty in identifying broadly applicable molecular markers. Fortunately, potato is amenable to propagation via tissue culture and it is relatively easy to introduce new traits using currently available biotech transformation techniques. For these reasons, potato is arguably the crop that can benefit most by modern biotechnology. The benefits of biotech potato, such as limited gene flow to conventionally grown crops and weedy relatives, the opportunity for significant productivity and nutritional quality gains, and reductions in production cost and environmental impact, have the potential to influence the marketability of newly developed varieties. In this review we will discuss current and past efforts to develop biotech potato varieties, traits that could be impacted, and the potential effects that biotech potato could have on the industry.

Full text

INVITED REVIEW
Biotech Potatoes in the 21st Century: 20 Years Since the First
Biotech Potato
Dennis Halterman
1
&Joe Guenthner
2
&Susan Collinge
3
&
Nathaniel Butler
4
&David Douches
4
#The Author(s) 2015. This article is published with open access at Springerlink.com
Abstract Potato is the world's most important vegetable crop,
with nearly 400 million tons produced worldwide every year,
lending to stability in food supply and socioeconomic impact.
In general, potato is an intensively managed crop, requiring
irrigation, fertilization, and frequent pesticide applications in
order to obtain the highest yields possible. Important traits are
easy to find in wild relatives of potato, but their introduction
using traditional breeding can take 15–20 years. This is due to
sexual incompatibility between some wild and cultivated spe-
cies, a desire to remove undesirable wild species traits from
adapted germplasm, and difficulty in identifying broadly ap-
plicable molecular markers.Fortunately, potato is amenable to
propagation via tissue culture and it is relatively easy to intro-
duce new traits using currently available biotech transforma-
tion techniques. For these reasons, potato is arguably the crop
that can benefit most by modern biotechnology. The benefits
of biotech potato, such as limited gene flow to conventionally
grown crops and weedy relatives, the opportunity for signifi-
cant productivity and nutritional quality gains, and reductions
in production cost and environmental impact, have the poten-
tial to influence the marketability of newly developed varie-
ties. In this review we will discuss current and past efforts to
develop biotech potato varieties, traits that could be impacted,
and the potential effects that biotech potato could have on the
industry.
Resumen La papa es el cultivo hortícola más importante en
el mundo, con cerca de 400 millones de toneladas producidas
a nivel mundial anualmente, acreditando la estabilidad en el
suministro de alimentos e impacto socioeconómico. En gen-
eral, la papa es un cultivo manejado intensivamente, que
requiere riego, fertilización y aplicaciones frecuentes de
plaguicidas para obtener los más altos rendimientos posibles.
Los caracteres importantes son fáciles de encontrar en
parientes silvestres de la papa, pero su introducción usando
el mejoramiento tradicional puede llevar de 15 a 20 años.
Esto es debido a la incompatibilidad sexual entre algunas
especies silvestres y cultivadas, el deseo para eliminar
características indeseables de las especies silvestres del
germoplasma adaptado, y la dificultad en la identificación
de marcadores moleculares aplicables ampliamente.
Afortunadamente, la papa es receptiva a la propagación por
cultivo de tejidos y es relativamente fácil la introducción de
nuevos caracteres usando técnicas biotecnológicas de
transformación actualmente disponibles. Por estas razones,
la papa es probablemente el cultivo que se puede beneficiar
mayormente por la biotecnología moderna. Los beneficios de
la papa biotecnológica, como el flujo genético limitado a
cultivos que se siembran convencionalmente y a los parientes
como malezas, la oportunidad para productividad
significativa y logros en calidad nutricional, y las reducciones
en los costos de producción e impacto ambiental, tienen el
potencial para influenciar la comercialización de las más
nuevas variedades desarrolladas. En esta revisión
discutiremos los esfuerzos actuales y pasados para desarrollar
variedades biotecnológicas de papa, rasgos que pudieran
impactarse, y los efectos potenciales que la papa
biotecnológica pudiera tener en la industria.
*Dennis Halterman
dennis.halterman@ars.usda.gov
1
Vegetable Crops Research Unit, U.S. Department of Agriculture,
Agricultural Research Service, Madison, WI 53706, USA
2
Department of AERS, University of Idaho, Moscow, ID 83844-2334,
USA
3
Plant Sciences, J.R. Simplot Company, Boise, ID 83706, USA
4
Department of Plant, Soil, and Microbial Sciences, Michigan State
University, East Lansing, MI 48824, USA
Am. J. Potato Res.
DOI 10.1007/s12230-015-9485-1

Keywords Potato .Genetic modification .Stress resistance
traits .Tuber quality traits
Introduction
Since the introduction of the first genetically modified (GM)/
biotech crop plants in the mid-1990s, the agriculture industry
has seen a steady increase in the acreage of those crops planted
and harvested worldwide each year. In 2014, a record 18 mil-
lion farmers in 28 countries planted 447 million acres of bio-
tech soybean, maize, cotton, canola, zucchini squash, papaya,
alfalfa, poplar, sugar beet, tomato, eggplant, and sweet pepper
(James 2014). This represents a more than 100-fold increase
in usage between 1996 and 2014. This increase is largely due
to the economic, environmental, and productivity benefits de-
rived from their use.
The vast majority of biotech crops grown worldwide con-
tinue to be used primarily for animal feed (soybean, maize,
alfalfa) or for fiber products that are not directly consumable
(cotton), although many of the foods we eat contain ingredi-
ents derived from biotech crops (e.g., oils, starches, sugars).
The appearance of direct-to-consumer biotech crops on the
market is increasing as biotech sweet corn, wheat, apple, pa-
paya, and potato have already completed or are currently
awaiting the completion of the regulatory clearance process.
The generation of new biotech crops has been hindered pri-
marily by costs associated with their development and regu-
latory clearances. Estimates place the cost of bringing a new
biotech crop to market at around $136 million, with the largest
cost associated with trait discovery (McDougall 2011). The
costs associated with the development of a new biotech crop
variety make it difficult for research scientists to carry out the
entire process without industry and market support (Miller and
Bradford 2010). However, in some cases where a devastating
disease threatens crops, we have seen the relatively rapid re-
lease and acceptance of biotech crops containing resistance,
such as with virus resistant Rainbow papaya (Gonsalves
1998).
In the U.S., potato annually accounts for $4.2 billion in
production value and the crop is grown on just over a million
acres (NASS 2015). Potato is an ideal crop for the introduction
of traits using biotechnology. In fact, after virus-resistant to-
bacco (China in 1992) and the FlavrSavr tomato (U.S. in
1994), potato was one of the first crops to be genetically mod-
ified; it was grown commercially as NewLeaf
TM
by Monsanto
in 1995. Conventional potato breeding as it is practiced world-
wide is an inefficient, slow process that has changed little in
the past century. Potato requires considerable inputs of nutri-
ents, pesticides, and water to maintain yield, quality, and pro-
tection from diseases and insects. Potato breeding efforts have
historically focused on yield, fresh market and processing
quality, and storability as well as disease resistance. Genetic
variation for these traits in commercial cultivars is low, but
related wild species contain many traits not found in cultivars
and represent an especially rich source of disease resistance
and tuber quality genes (Hanneman 1989;Jansky2000).
Efforts have been made to introgress nutritional qualities and
resistance to pests and abiotic stresses from wild species into
cultivated potato, but popular cultivars have few traits derived
from wild germplasm due to their genetic complexity, unpre-
dictable expression in adapted backgrounds, and a desire by
industry to limit variability in processing quality (Hirsch et al.
2013). In the U.S., the availability of effective pesticides, fun-
gicides, fumigants, synthetic fertilizers, and irrigation systems
has meant that market-driven traits, such as yield, are often
given higher priority than biotic and abiotic stress resistances.
Combining tuber quality traits desired by consumers and pro-
cessors with the agronomic performance and disease resis-
tance preferred by farmers remains the most significant chal-
lenge in potato breeding. Fortunately, the tremendous amount
of genetic diversity in wild and cultivated relatives of potato
allows for relatively easy identification, isolation, and intro-
duction of new genes for a specific trait using biotechnology.
For example, genes from wild potato relatives can contribute
resistanceto late blight, Verticillium wilt, potato virus Y, water
stress, and cold-induced sweetening (see following discus-
sion). The fact that genes of interest can be derived from wild
relatives of potato allows for the production of biotech varie-
ties by inserting potato DNA. This is contrasted with tradition-
al transgenic plants that use DNA derived from bacteria, vi-
ruses, or other organisms.
In addition to the abundance of traits available for potato
improvement, potato can be propagated easily in tissue cul-
ture, making it straightforward to integrate specific genes
and recover plants from transformed tissue (Chakravarty
et al. 2007). Some cultivars are more amenable to tissue
culture than others, but with appropriate protocol modifica-
tions, most are capable of undergoing transformation using
Agrobacterium tumefaciens and regeneration of plant tissue.
The use of Agrobacterium to introduce genes of interest is
themostcommonmethodofstabletransformationinpotato,
although other methods such as particle bombardment, pro-
toplast transformation, and microinjection have been suc-
cessful. Regardless of the method, these approaches require
regulatory clearance of the resulting potato variety before
wide-scale release and production. Regulatory clearance in
the U.S. can involve up to three federal agencies: the
Environmental Protection Agency (EPA), the Food and
Drug Administration (FDA), and the US Department of
Agriculture (USDA). Relatively new methods to specifically
edit regions of the plant genomes are also being developed
and may provide a method for genetic improvement that fits
outside the traditional regulatory process (Waltz 2012).
Companies specializing in gene editing, such as Calyxt (for-
merly Cellectis Plant Sciences), are using these new tools to
Am. J. Potato Res.

modify specific traits in tetraploid potato (Clasen et al.
2015).
The biotech potatoes commercialized in the mid-1990s
(Toevs et al. 2011b) were a technological success and provid-
ed benefits to producers, consumers, and the environment, but
anti-GMO pressure regarding the safety of biotech food crops
led to their removal from the market in 2002, and their status
remained unchanged for more than a decade. With the wide-
spread approval and adoption of other biotech crops, there is a
renewed interest in the development of biotech potato which
has led to the arrival of biotech potatoes back on the market in
2015.
The purpose of this review is to provide readers with an
overview of biotech potato including its history, past and po-
tential impact on the industry, targeted traits, consumer per-
ception, and biotech crop safety. Genetic modification of po-
tato to introduce agronomic-, production-, and consumer-
oriented traits has led to an opportunity to revolutionize potato
breeding and offer an alternative to traditional variety selec-
tion methods. We are hopeful that market acceptance of the
technology will increase efforts towards the discovery of
genes that could be used to improve current varieties. The
use of biotechnology will provide a much-needed avenue for
the introduction of unique traits present in wild potato rela-
tives, which would typically be difficult or impossible to in-
troduce into cultivated potato using traditional methods.
History of Biotech Potato
In 1995 Monsanto released the first biotech potato used in
agricultural production, the Russet Burbank variety contain-
ing the CryIIIA gene to provide resistance to Colorado Potato
Beetle (CPB; USDA-APHIS 2015). Named NewLeaf
TM
,this
marked the introduction of the company’s first biotech crop of
any type. NatureMark, a wholly-owned subsidiary of
Monsanto, eventually marketed three varieties of CPB-
resistant potato –Atlantic, Russet Burbank, and Superior –
and branded them with the NewLeaf™trademark. In regions
where CPB was a problem, NewLeaf™potatoes quickly be-
came popular among growers. The product was very effective
at preventing CPB damage and U.S. plantings of NatureMark
potatoes expanded rapidly, from 1,800 acres in 1995 to 55,000
acres in 1998. Three years after rolling out its biotech pota-
toes, NatureMark varieties comprised four percent of the U.S.
crop. By 1991, Monsanto had developed potatoes resistant to
both CPB and potato leafroll virus (PLRV) (Perlak et al. 1993;
Kaniewski and Thomas 2004). In 1998, NatureMark intro-
duced NewLeaf Plus
TM
, a Russet Burbank variety with resis-
tance to both CPB and PLRV.
Other NatureMark products in development at that time
included resistance to late blight and tubers with increased
specific gravity (Kaniewski and Thomas 2004). Not
surprisingly, Monsanto was not the only organization
investing in biotech potatoes. Scientists with other firms and
universities around the world were conducting research and
field testing biotech potatoes. Much of theeffort went into pest
resistance, especially late blight resistance, but processing
traits were also targets.
Anti-GMO activism fueling public debate regarding the
safety of biotech crops eventually led to problems with mar-
keting NewLeaf™potatoes used for processing. The food
industry, consumer groups, and anti-biotech activists, who
remained quiet at first, began voicing opposition to products
derived from biotech potato. Quick service restaurants reacted
by moving away from frozen fries made with biotech pota-
toes. Fueling the debate surrounding biotech potato products,
one frozen potato processor tried to differentiate its fries by
guaranteeing that they were GM-free (Guenthner 2001). The
North American fresh market continued to accept biotech po-
tatoes, but with processed potato markets closing, growers
became reluctant to take on the risk of planting biotech pota-
toes. Surrendering to dwindling marketability for their prod-
ucts, Monsanto closed its NatureMark potato business in the
Spring of 2001.
There were alsoproblems with other processed potato mar-
kets. Raw product for dehydrated potato processing comes
mostly from fresh packers who sort out potatoes that don’t
meet fresh quality standards. In the infancy of biotech crop
commercialization, there was no perceived need for an iden-
tity preservation (IP) or directed marketing program for
NewLeaf™potatoes. There was general mixing of biotech
and conventional potatoes within the dehydration supply
chain (Toevs et al. 2011a). Although Monsanto had received
Japanese government approvals for most NewLeaf™potato
varieties, when NewLeaf™potatoes were withdrawn from the
market, they were also withdrawn from domestic and interna-
tional regulatory processes. After withdrawal, an unapproved
event was found in dehydrated potatoes and the potato import
tolerance level for that event was 0 %. The consequences of
this action included rejected shipments and expensive product
testing for the North American potato industry.
At about the time thatMonsanto withdrew from the biotech
potato business, the J.R. Simplot Company began efforts on
product development, testing, and regulatory submissions.
Learning from the marketing difficulties encountered by
Monsanto, Simplot focused on consumer traits rather than
producer traits for its first biotech potato products. Simplot
also used only potato genes for trait introduction in order to
address the public’s concerns regarding biotech food safety.
One of the first consumer traits focused on by Simplot was
potatoes that had a lower propensity for the formation of ac-
rylamide, a substance linked to birth defects and cancer in
mice and rats (National Toxicology Program 2011), and com-
mon in foods cooked at high temperatures. Anticipating the
need for low-acrylamide raw product for its potato processing
Am. J. Potato Res.

business, Simplot scientists successfully developed potatoes
with a lower potential for producing acrylamide. A second
consumer trait of interest to Simplot was black spot bruise
resistance, which could reduce food waste during processing
and open new avenues for marketing fresh cut potatoes.
In 2013 Simplot submitted a petition to the U.S.
Department of Agriculture, Animal and Plant Health
Inspection Service (USDA-APHIS 2015) seeking nonregulat-
ed status for its Innate
TM
1.0 potato with low acrylamide po-
tential and black spot bruise resistance traits. In 2014, Simplot
received deregulation from the USDA. This was followed by
completing the food and feed safety consultation with the
Food and Drug Administration (FDA) in 2015, opening the
door for Simplot to commercialize Innate
TM
1.0 in Atlantic,
Ranger Russet, and Russet Burbank potatoes.
In May 2015, the Innate
TM
1.0 potatoes entered the fresh
and chip market channels as a limited commercial launch.
Simplot implemented a directed marketing stewardship pro-
gram to keep the biotech potatoes out of the dehydration and
frozen processing market channels. The company also submit-
ted a petition to USDA APHIS for Innate
TM
2.0 potatoes that
have the same 1.0 traits but add late blight resistance and cold
storage capability.
Efforts to develop and commercialize biotech potatoes con-
tinue around the globe, but outside North America only three
varieties have received government approval as of May 2015
(ISAAA 2015). One is Amflora, a high-starch potato devel-
oped by BASF and approved in Europe, but no longer
marketed. The other two, Elizaveta Plus and Lugovskoi
Plus, are insect-resistant varieties developed by the Russian
Academy of Sciences. Other biotech potato varieties have
been developed, but have not completed regulatory clear-
ances. In addition to Amflora, BASF also developed the vari-
eties Modena, Amadea (both with increased amylopectin),
and Fortuna (with late blight resistance). However, BASF
halted its pursuit of regulatory approval of all biotech potato
varieties in 2013 Bbecause continued investment cannot be
justified due to uncertainty in the regulatory environment
and threats of field destructions^(BASF 2013).
The perseverance of biotech potato development and mar-
keting should serve as a clear indication of the desire for im-
proved potato varieties by growers and producers. Consumer
acceptance of biotechnology is increasing and the coupling of
new technologies with an increasingly scientifically literate
public and a focus on consumer-oriented traits should favor
widespread approval of biotech potato on the marketplace.
Traits for Biotech Potato Development
The integration of new traits into potato using biotech-
nology has some advantages and disadvantages com-
pared to using traditional breeding to accomplish the
same goal. Traditional breeding methods allow for
crossing of two heterozygous tetraploid parents with
widely different phenotypic assortments, with the expec-
tation that a small percentage of the offspring will con-
tain at least some of the desirable traits of both parents.
Typically, progeny are then evaluated in the field to
remove undesirable clones. This allows for the chance
to introduce multiple desirable traits, especially when
using parents that have contrasting appealing qualities.
However, this process also allows for the incorporation
of undesirable traits that must subsequently be selected
against and, therefore, it can take a long time (10–
15 years) to produce a new marketable potato cultivar
following the initial cross. The use of molecular
markers associated with the desired traits can signifi-
cantly speed up this process. New DNA sequencing
technologies have facilitated the identification of thou-
sands of potential markers for cultivated potato, but
these markers must first be correlated with the selected
trait (Hamilton et al. 2011) and then used to develop a
laboratory-friendly (typically PCR based) method for
their identification in segregating populations.
In contrast to traditional breeding, the time needed to intro-
duce a specific gene into potato using Agrobacterium, follow-
ed by regeneration of the whole plant, is only 6–12 months. In
addition, the targeted germplasm used for transformation can
be an existing cultivar that already contains desirable agro-
nomic characteristics and produces tubers with superior post-
harvest processing qualities. Stable integration of
Agrobacterium transfer DNA inserts of up to around 150 ki-
lobases of DNA into a plant genome has been reported
(Hamilton et al. 1996), which would allow for the introduction
of multiple genes simultaneously. A disadvantage of using
biotechnology for trait integration is that the gene(s) ofinterest
must first be identified and cloned, which requires consider-
able expertise and effort. Genes that are expressed in a dom-
inant fashion are of particular interest since backcrossing to
achieve homozygosity is not required. However, gene silenc-
ing approaches allow for reduction in the expression of spe-
cific genes, resulting in a dominant negative effect (Pandey
et al. 2015), eliminating the need to achieve homozygosity for
traits that are normally inherited recessively, such as resistance
to some diseases.
There are far too many published reports using bio-
tech potato for gene characterization and trait incorpora-
tion to attempt to discuss all of them in this review.
Therefore, this article focuses on traits that are currently
being used to develop biotech potato lines or those that
show potential to impact the marketability of biotech
potato varieties in the future, with a particular interest
on traits that can be addressed through the manipulation
of gene expression or by using genes from potato and its
close relatives.
Am. J. Potato Res.

Resistance to Biotic and Abiotic Stresses
The introduction of pest resistance into cultivated varieties
would reduce pesticide applications. Similarly, manipulation
of gene expression that regulates water use efficiency in potato
would allow for increased performance under water deficit
conditions. Fortunately, collections of wild and cultivated po-
tato germplasm are diverse and many wild species possess
resistance to economically important diseases. Resistance to
diseases is relatively easy to integrate because most traits are
single genes that are inherited in a dominant fashion. Single
genes can have a dramatic effect on the host when the patho-
gen is present, but rapid evolution of some pathogen geno-
types has led to a breakdown of disease resistance after de-
ployment. Our ability to use biotechnology to rapidly deploy
stress resistance in popular cultivars and combine multiple
genes for resistance offers certain advantages over traditional
breeding.
Pattern Recognition Receptors Plants have a two-tiered de-
fense system. The first layer of defense includes the recogni-
tion of certain pathogen byproducts (such as fungal chitin and
bacterial flagellin or EFTu proteins) termed pathogen associ-
ated molecular patterns (PAMPs; reviewed by Zipfel 2014).
PAMPs are recognized by receptor proteins located on the
surface of the host cell. These pattern recognition receptors
(PRRs) recognize the presence of PAMPs and activate defense
responses. Interfamily transfer of PRRs has shown to produce
resistance in the target plant and this increases the application
potential of these genes in biotech crops. For example, the
Brassicaceae-specific EFR protein, which recognizes bacterial
EFTu, can increase bacterial resistance in the Solanaceous
plants tomato and Nicotiana benthamiana (Lacombe et al.
2010). Similarly, the Arabidopsis lectin receptor kinase
LecRK1.9 is able to confer increased resistance to
P. infestans when expressed in potato and N. benthamiana
(Bouwmeester et al. 2014).
Although it is likely that many PRRs exist in potato, the
only PRR that has been identified so far is the ELR protein,
which recognizes the presence of the INF1 elicitin from
P. infestans (Du et al. 2015). Other PRRs have been identified
in closely related tomato and include EIX2 (recognizing fun-
gal xylanase; Ron and Avni 2004), Ve1 (recognizing the Ave1
protein from Verticillium dahliae; Fradin et al. 2009), and Cf-9
(recognizing the AVR9 peptide from Cladosporium fulvum;
Jones et al. 1994). Given the fact that PRRs are capable of
interfamily transfer, it is likely that PRRs from within the
Solanaceae family could increase disease resistance in potato.
In fact, the tomato Ve1 gene when expressed in potato confers
resistance to Verticillium dahliae (Kawchuk et al. 2001).
Disease Resistance Genes The second layer of plant defense
relies on the function of resistance (R) proteins that recognize
specific pathogen molecules, termed effectors. The plant de-
fense responses that are elicited by PRR and R proteins are
similar, but R proteins typically elicit a stronger response,
culminating in programmed cell death termed the hypersensi-
tive response, which functions to limit spread of the pathogen.
Pathogen effectors are highly diverse in function and molec-
ular structure. In contrast, most R proteins share a similar
overall structure and encode proteins with nucleotide binding
(NB) and leucine-rich repeat (LRR) domains. For this reason,
most plant R protein candidates are immediately recognizable,
which could potentially facilitate their identification once ge-
nomic locations responsible for resistance are known, or by
using homology-based identification of candidate genes
(Vossen et al. 2013).
The identification and cloning of several genes for resis-
tance to the late blight pathogen Phytophthora infestans
from wild relatives of cultivated potato has been published
within the past 15 years. For example, R1,R2,andR3a
from Solanum demissum (Ballvora et al. 2002; Huang et al.
2005; Lokossou et al. 2009), Rpi-blb1,Rpi-blb2 and Rpi-
blb3 from S. bulbocastanum (Song et al. 2003; van der
Vossen et al. 2003,2005; Lokossou et al. 2009), Rpi-
vnt1.1 from S. venturii (Foster et al. 2009; Pel et al.
2009), and Rpi-mcq1 gene from S. mochiquense (Jones
et al. 2009) all provide resistance to individual or multiple
strains of P. infestans (Fig. 1). The discovery of these genes
has led to the identification of functionally equivalent var-
iants derived from other wild potato species, such as RB
ver
,
Rpi-sto1,andRpi-pta1 from S. verrucosum,S. stoloniferum,
and S. papita, respectively, which are related to Rpi-blb1
(Liu and Halterman 2006; Vleeshouwers et al. 2008).
These additional genes provide supplementary genetic var-
iation that could be used in the development of late blight
resistant cultivars. In 2011, BASF petitioned for release of
a biotech late blight resistant potato named Fortuna.
Fortuna contains two resistance genes, Rpi-blb1 (RB)and
Rpi-blb2. However, as mentioned previously Fortuna potato
never made it to market. The second generation of
Simplot’s Innate
TM
potato will incorporate late blight
resistance.
In addition to the numerous late blight Rgenes iso-
lated from wild potato relatives, several other Rgenes
have been cloned. The Rx1 and Rx2 genes from
S. tuberosum ssp. andigena and S. acaule,respectively,
confer resistance to potato virus X (Bendahmane et al.
1997,2000), the Gro1-4gene from S. spegazzinii con-
fers resistance to the root cyst nematode Globodera
rostochiensis (Paaletal.2004), and the Gpa2 gene
from S. tuberosum ssp. andigena confers resistance to
the pale cyst nematode G. pallida. Although potato R
genes have been identified for a only few diseases so
far, this avenue of research remains a priority in many
laboratories around the world.
Am. J. Potato Res.

The NB-LRR class of disease Rgenes is typically found
within gene clusters that contain both functional and nonfunc-
tional alleles (Michelmore and Meyers 1998), and susceptible
hosts can also harbor nonfunctional Rgenes with a high de-
gree of sequence similarity to the functional variant. For these
reasons, the development of molecular markers for Rgenes
that are both allele specific and broadly applicable across dif-
ferent genetic backgrounds has proven difficult. Therefore, the
isolation of Rgenes through map-based cloning and their in-
troduction using stable transformation provides a rapid and
reliable way to quickly introduce disease resistance into elite
cultivars.
Other Genes Conferring Disease Resistance In addition to
PRR and R proteins, other genes and mechanisms have the
potential to be used to increase disease resistance in potato
using biotechnology. One such example is the eIF4E gene that
has been found to be associated with virus resistance in many
plant species (Nicaise et al. 2003; Gao et al. 2004; Yoshii et al.
2004;Kangetal.2005; Kanyuka et al. 2005; Stein et al. 2005;
Nieto et al. 2006,2007; Ibiza et al. 2010; Naderpour et al.
2010; Piron et al. 2010), including resistance to potato virus
Y in potato, tomato, and pepper (Ruffel et al. 2002,2005;
Cavatorta et al. 2011;Duanetal.2012). Variants of eIF4E
confer resistance to PVY in the potato wild species relatives
S. chacoense,S. demissum,andS. etuberosum (Duan et al.
2012), permitting the eventual use of this gene in future bio-
tech potato varieties. Unlike PRR or R proteins, the eIF4E
protein does not recognize the presence of a specific pathogen
molecule to elicit resistance. Instead, it is a host protein re-
quired for proper translation of the viral genomic RNA.
Mutations within eIF4E render the protein unusable by the
virus and therefore the virus is unable to replicate within the
plant cell (Ruffel et al. 2002). In pepper and tomato, eIF4E-
mediated resistance is inherited in a recessive manner (Ruffel
et al. 2002,2005). However, introduction of the pepper gene
into tomato or potato results in resistance that is dominant over
the expression of the endogenous eIF4E variant (Kang et al.
2007; Cavatorta et al. 2011), demonstrating that deployment
of eIF4E-based resistance from wild relatives into tetraploid
potato is feasible without the need for removal or silencing of
the endogenous susceptible allele. The mechanism by which
the introduction of this eIF4E using biotechnology results in a
switch from recessive to dominant resistance is not well un-
derstood and is currently a focus of multiple research projects.
It is well known that overexpression of virus genes in host
plants can lead to increased resistance (reviewed by Goldbach
et al. 2003). In papaya, transgenic plants expressing the coat
protein from papaya ringspot virus led to increased resistance
and saved the threatened Hawaiian papaya industry
(Gonsalves et al. 2004). Scientists are now trying to use a
similar approach to target other plant pathogens. Host induced
gene silencing (HIGS) is a relatively new approach for con-
trolling plant pathogens that relies on RNA interference to
target the expression of essential pathogen genes. This strate-
gy has been used to target a wide range of pathogen types
including insects (reviews by Baum et al. 2007; Huvenne
and Smagghe 2010), nematodes (reviewed by Huang et al.
2006; Yadav et al. 2006; Fairbairn et al. 2007; Sindhu et al.
2009), fungi (Nowara et al. 2010; Tinoco et al. 2010; Yin et al.
2011; Zhang et al. 2012;Kochetal.2013; Panwar et al. 2013;
Pliego et al. 2013;Ghagetal.2014), parasitic weeds (Tomilov
et al. 2008), and oomycetes (Govindarajulu et al. 2014; Vega-
Arreguin et al. 2014; Jahan et al. 2015). Pathogen effectors
essential for virulence or Bhousekeeping^genes necessary for
normal pathogen growth are typically the targets for HIGS.
The expression of gene fragments that result in the production
of small interfering RNAs (siRNAs) are expressed in the host
plant. The siRNAs subsequently move into the pathogen dur-
ing infection to silence the target genes. In the only HIGS
results using potato thus far, targeting of the P. infestans gene
hp-PiGPB1, which encodes a protein important in pathoge-
nicity, resulted in reduced sporangia formation and disease
progression in transgenic plants (Jahan et al. 2015). Not only
does HIGS provide an experimental tool for determining the
significance of specific genes in pathogen virulence, it also
presents a new way to control plant diseases without having
to identify and clone Rgenes from the host. Additionally, by
targeting genes that are essential for pathogen growth, rather
than disposable effector targets, HIGS could provide more
durable resistance, as it would be more difficult for these path-
ogen genes to be eliminated without impacting overall
Fig. 1 Cultivar ‘Superior’(left)
and ‘Superior’expressing the RB
(Rpi-blb1) gene 3 weeks after
inoculation with the late blight
pathogen Phytophthora infestans
Am. J. Potato Res.

viability. Due to the fact that foreign gene fragments are being
expressed in the host plant, it is likely that plants expressing
HIGS constructs would need regulatory clearance prior to
release.
Drought Resistance Most modern varieties of potato are con-
sidered drought susceptible (Mackerron and Jefferies 1988;
Weisz et al. 1994;Yuanetal.2003; Cabello et al. 2012;
Monneveux et al. 2013) but variation does exist in landraces
and wild relatives (Cabello et al. 2012). In Arabidopsis
thaliana, manipulation of abscisic acid signal transduction
through loss of function of the cap-binding protein 20
(CBP20) leads to increased drought tolerance (Papp et al.
2004). CBP20 interacts with the cap-binding protein 80
(CBP80) to form an active complex that is translocated to
the nucleus (Kierzkowski et al. 2009). Silencing of CBP80
in potato cultivar Desiree led to a higher tolerance to drought
(Pieczynski et al. 2013), indicating a promising target for fu-
ture biotech potato varieties that require less water inputs.
Tuber Quality Traits
Lower Acrylamide Acrylamide, which is produced in starch-
rich foods processed under high temperatures, is a concern
because it can cause cancer in laboratory animals at high
doses, and is Breasonably anticipated to be a human
carcinogen^(National Toxicology Program 2011). Potato
chips and french fries provide a significant dietary contribu-
tion to acrylamide levels (Becalski et al. 2003). This has raised
a worldwide food safety concern that has resulted in lawsuits
against major potato and quick serve restaurant companies
under California’s Safe Drinking Water and Toxic
Enforcement Act of 1986, also known as Proposition 65
(Office of Environmental Health Hazard Assessment 2015).
Acrylamide was added to Proposition 65 in 1990, which re-
quires businesses to warn Californians about the presence of
chemicals that may cause cancer or reproductive toxicity in
the products they purchase through labeling at restaurants or
on product packaging. The substrates for the production of
acrylamide are reducing sugars (glucose and fructose) and
the amino acid asparagine. Consequently, one biotech strategy
has focused on suppressing the accumulation of reducing
sugars by down-regulating the production of the enzyme acid
invertase, which cleaves sucrose into glucose and fructose
(see below). This strategy has been very successful in
transforming standard chip cultivars into clones with high
levels of resistance to cold sweetening (Bhaskar et al. 2010;
Ye et al. 2010). Another strategy to reduce acrylamide levels
in processed potato products is to reduce expression of two
genes required for asparagine synthesis (Chawla et al. 2012).
The first generation of Simplot’sInnate
TM
potato variety com-
bines lower reducing sugar levels and decreased asparagine to
address potential acrylamide issues (Simplot 2013).
Black Spot Bruise Resistance Tuber blackspot caused by
impact and pressure during harvest and storage, as well as
tuber tissue browning after cutting, is caused by the oxidation
of phenolic compounds by the enzyme polyphenol oxidase
(PPO) to quinones, which polymerize to cause dark pigmen-
tation (Stevens and Davelaar 1997). Silencing of PPO genes in
potato leads to a reduction in enzymatic browning of tuber
tissue due to wounding and bruising from impact (Bachem
et al. 1994; Coetzer et al. 2001; Chi et al. 2014). Innate
TM
potato will contain black spot bruise resistance through
down-regulation of PPO (Fig. 2).
Cold Induced Sweetening Resistance Several tuber quality
defects are caused by the accumulation of the reducing sugars
glucose and fructose. These defects include cold-induced
sweetening during storage at temperatures of less than
~10 °C, sugar-end defect, and stem-end chip defect. At high
temperatures, such as those reached during frying, reducing
sugars react with amino acids in a non-enzymatic, Maillard
reaction to produce dark-colored pigments (Benzing-Purdie
et al. 1985). Chips and fries made from tubers with elevated
reducing sugar contents are unacceptably dark in color and
may have an undesirable bitter flavor. Silencing of the potato
vacuolar acid invertase gene VInv prevents the accumulation
of reducing sugar in tubers stored at cold temperatures (Fig. 3;
Bhaskar et al. 2010). Similarly, overexpression of the vacuolar
invertase inhibitor INH2 reduces acid invertase activity and
the accumulation of reducing sugars in stored tubers
(McKenzie et al. 2013).
Increased Amylopectin in Starch Conventional potato
starch is composed of 80 % amylopectin and 20 % amylose.
While the more prevalent amylopectin contains the properties
needed by industry (adhesives, textiles, paper, construction
materials, etc.), the presence of amylose in potato starch leads
to problems in many technical applications. Therefore, potato
starch requires pretreatment to modify amylose before it is
suitable for industrial applications. The Amflora potato was
developed by BASF, who petitioned for regulatory clearance
in 1997. Thirteen years later, Amflora potato received
Fig. 2 Comparison of an Innate
TM
potato with a silenced polyphenol
oxidase gene (left) and a traditional potato (right) 10 h after being cut
Am. J. Potato Res.

European approval for commercial cultivation, which was the
first genetically modified crop to receive EU approval since
1998. By silencing the granule bound starch synthase (GBSS)
gene that controls amylose synthesis (Visser et al. 1991),
Amflora potatoes contain only amylopectin. Another amylo-
pectin potato variety, named Modena, was developed by the
Dutch company AVEBE. In 2011, AVEBE passed ownership
of Modena to BASF. A second generation of amylopectin
potato, named Amadea, also was developed by BASF and
was expected to eventually replace Amflora cultivation.
However, as mentioned previously, BASF discontinued its
pursuit of biotech potato regulatory clearance in 2013.
Nutrition
Vitamin C Our intake of ascorbate, or vitamin C, is primar-
ily obtained through consumption of fruits and vegetables.
While potato tubers contain ascorbate, they are a relatively
poor source. A half cup (61 g) serving of baked potato
provides only about 8 mg of the recommended daily intake
of 40–90 mg per day (USDA Nutrient Data Laboratory
2015). However, potato is capable of producing increased
levels of ascorbate (Hemavathi et al. 2010; Bulley et al.
2012), leading to an opportunity to genetically enhance pop-
ular varieties to provide additional Vitamin C our diets.
Bulley et al. (2012) reported an up to threefold increase in
ascorbate through the overexpression of a single potato
gene, GDP-L-galactose phosphorylase.
Vitamin A Beta-carotene is the primary substate for synthesis
of vitamin A in humans. Most potatoes are a poor source of
beta-carotene, although some lines produce high levels of ze-
axanthin, a xanthophyll that is derived from beta-carotene by
the activity of the enzyme beta-carotene hydroxylase (BCH;
Brown et al. 1993).By silencing the BCH gene in potato using
RNAi, Van Eck et al. (2007) were able to significantly in-
crease beta-carotene content of tubers, even in lines that nor-
mally accumulate only low levels of zeaxanthin. Although the
beta-carotene levels reached in these lines were lower than
carotenoid-rich vegetables such as carrots or sweet potatoes,
biofortification of potatoes offers an opportunity to provide
added nutritional benefits to a food source that is already pop-
ular globally.
Glycoalkoloids Glycoalkaloids produced in potatoes (primar-
ily α-solanine and α-chaconine) can contribute positively to
potato flavor, but at higher levels contribute to bitterness and
toxicity. Wounding and light exposure are known to affect
glycoalkaloid content, which could lead to levels beyond the
threshold of 20 mg per 100 g fresh weight (Petersson et al.
2013), the level considered safe for human consumption
(Smith et al. 1996). Many wild species of potato naturally
produce high levels of glycoalkaloids (Gregory et al. 1981),
leading to a need to monitor glycoalkaloid content when in-
troducing other traits from these species. Therefore breeders
must be mindful of glycoalkaloid levels when using wild spe-
cies to develop germplasm. Silencing of the gene encoding a
sterol alkaloid glycosyltransferase led to almost complete
elimination of α-solanine, with a correlated increase in α-
chaconine in some lines but not others (McCue et al. 2005).
The Future of Trait Development and Incorporation
Using Biotechnology
As we continue to understand how biotic and abiotic stresses
affect normal growth of crop plants such as potato, and iden-
tify the genes involved in resistance, opportunities to engineer
new varieties using biotechnology will continue to arise.
Many major genes for resistance to various diseases and abi-
otic stresses have already been mapped in potato germplasm
and their cloning is inevitable. Using biotechnology to incor-
porate stress resistance genes provides certain advantages over
conventional breeding. This includes 1) the relatively rapid
development of new varieties once genes have been cloned.
Plant pathogens can evolve quickly to overcome resistance
and our ability to rapidly deploy novel genes is important to
combat epidemics if they arise; 2) the ability to include mul-
tiple Bmodes of action^, for example pyramiding PRR and R
Fig. 3 Chips from tubers of wild-type Katahdin (a) and Katahdin with
reduced expression of the vacuolar acid invertase gene (b) after being
stored at 3 °C for 6 weeks. Chips made from tubers of wild-type
MegaChip (c) and MegaChip with reduced expression of VInv (d)after
storage at 3 °C for 16 weeks. Photos provided by Amy Wiberley-
Bradford and Paul Bethke
Am. J. Potato Res.

genes that recognize different molecules from the same path-
ogen, would make it more difficult for the pathogen to evolve
to overcome resistance; 3) the addition of resistance from wild
relatives without the incorporation of undesirable traits linked
to the gene(s) of interest; and 4) an ability to quickly adapt
existing varieties to new environments and markets that arise
due to changing climates. Due to the fact that disease resis-
tance proteins are considered biopesticides, biotech varieties
with novel disease resistance genes fall under EPA authority.
However, R proteins are clear examples of intractable pro-
teins, as they are difficult or impossible to detect in plant tissue
due to their low level of expression. Therefore, due to a very
low level of exposure to R proteins and therefore low risk,
safety assessments should consider these characteristics in
similar disease resistant varieties (Bushey et al. 2014).
The genetic basis of complex agronomic traits such as fla-
vor and texture, maturity, and yield is currently challenging to
define in potato, as effective screens are difficult or many
genes could be involved in the phenotypes. Quantitative traits
such as these may be difficult to address using biotechnology,
as the identification, isolation, and introduction of many
genes, each with a minor contribution to the desired pheno-
type, would prove to be a difficult undertaking. However, as
we continue to better understand the genes involved in com-
plex traits and develop new tools for genetic modification,
engineering varieties with desired complex traits should be
achievable.
The future of biotech potato is reliant not only on traits
important for improvement of the crop, but also on market
acceptance, which is driven ultimately by consumers. While
consumer oriented traits such as fortified nutrition, enhanced
flavor, and superior appearance seem minor when considering
the entire scope of potato production, we believe that it is these
traits that will ultimately drive long-term acceptance of bio-
tech potato. We are adopting the premise that using biotech-
nology to directly enhance our food in beneficial ways, rather
than focusing solely on production oriented traits such as her-
bicide tolerance or disease resistance, will be favored by con-
sumers and facilitate widespread market acceptance.
Regulatory Clearances for New Biotech Products
Agencies Regulating Biotechnology in the U.S
U.S. biotech regulatory responsibility falls within the
USDA, FDA, and EPA under a program called The
Coordinated Framework for Regulation of Biotechnology
(Office of Science and Technology Policy 1986). The
USDA evaluates biotech crops through the Biotechnology
Regulatory Services (BRS) group within the Animal and
Plant Health Inspection Service (APHIS). After a complet-
ed evaluation by the USDA, the biotech plants are no
longer regulated and termed deregulated. The USDA BRS
also regulates field trials of biotech crops and requires re-
searchers to follow proper permitting and notification pro-
cedures. The FDA’s authority for biotech crops falls under
the Federal Food, Drug, and Cosmetic Act. FDA encour-
ages a voluntary consultation process to ensure that food
and feed meet all safety and labeling obligations before
distribution. Although technically voluntary, all biotech
foods currently on the market in the U.S. have completed
the consultation process. In addition, EPA regulates plant
incorporated protectants (PIPs) under the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA). In
essence, such PIPs introduced through biotechnology are
regulated as biopesticides. The EPA regulates both the pes-
ticide and the genetic material necessary for its production.
EPA also establishes an exemption from the requirement of
a tolerance for residues of pesticides on and in food and
animal feed under the Federal Food, Drug and Cosmetic
Act. Regulatory clearance in the U.S. is necessary to allow
for product sales, but also sets the stage for international
approvals because some countries such as Mexico and
China require full authorization in a major cultivation mar-
ket prior to submission. In addition to regulatory authoriza-
tions, both USDA and EPA provide oversight and a review
process before conducting field trials.
USDA Petitions for Deregulation
Petitions for deregulation with the USDA naturally will be
focused on the authority of the agency under the Plant
Protection Act, to evaluate the new bioengineered plant, such
as the biotech potato, and determine it does not pose a plant
pest risk. Information that is evaluated to support such a de-
termination includes:
1) A rationale for the development of the biotech plant that
includes benefits of the trait;
2) Background on the plant biology, often using internation-
al consensus documents such as those created by the
Organization for Economic Co-operation and
Development (OECD 1997);
3) Description of the transformation system including the
donor genes;
4) Characterization of the genetic insert, including stability
and validation of transfer of only the desired DNA se-
quence to confer the traits;
5) Quantification of expressed protein(s) related to the traits;
6) Agronomic performance;
7) Compositional assessment; and
8) Environmental Safety.
The evaluation of submissions by BRS results in a Plant
Pest Risk Assessment and Environmental Assessment (EA).
Am. J. Potato Res.

Both assessments are made publicly available for comments
that are then considered by BRS before deregulation. This
entire process is open for public review and also serves as
informal guidance for future developers of biotech crops. If
BRS concludes that the new variety does not meet the require-
ments for a BFinding of No Significant Impact (FONSI)^after
conducting an EA, the agency may proceed with the more in
depth process of completing an Environmental Impact
Statement.
FDA Consultation Process
The voluntary review by FDA requires a submission much
like that for USDA, except that the evaluation for food and
feed safety does not require agronomic performance or an
environmental assessment. Unlike the USDA, documents
submitted to the FDA for this consultation are not readily
available to the public, however, they can be obtained via
the Freedom of Information Act. At the end of the review
process, the FDA publishes a Biotechnology Agency
Response Letter and a Consultation Note to the File on the
FDA website (FDA 2015). For the compositional assessment,
a comparison is made to determine if the biotech plant is not
meaningfully different from the control. In its recent review of
biotech potato, the FDA concluded in the Consultation Note
to the File that Innate™potatoes are not different in compo-
sition, safety, or any other relevant parameter from compara-
ble potato varieties now grown, marketed, and consumed in
the United States, except for the intended changes (FDA
2015). Unlike USDA and EPA, FDA has no specific require-
ments associated with releasing biotech crops into the envi-
ronment prior to commercialization.
EPA Regulatory Process
EPA regulations for biotech crops have been adapted from
guidelines that were written for microbial pesticides and ap-
plied them to Plant Incorporated Protectants (PIPs), the no-
menclature for modern biotechnology traits that confer pesti-
cidal or fungicidal activity, which include genes that confer
resistance to microbes. Both USDA and EPA oversee field
trials with biotech crops containing PIPs. Notifications with
USDA are expected before any biotech crop is planted in field
trials and crops containing PIPs must be registered with EPA
before commercial sales. A submission for FIFRA registration
includes the type of information expected for approval of a
pesticide. This includes the product identity, toxicity, and a
review of possible effects on humans, the environment, and
non-target organisms. As with pesticides, EPA sets tolerances
of maximum residue levels or exemption from the require-
ment of a tolerance for PIPs. All biotech crops registered with
EPA have established tolerance exemptions based on safety
assessments of the expressed proteins.
Regulatory Challenges Specific for Potatoes
Modifying potatoes through biotechnology has distinct ad-
vantages because of the extreme difficulty in breeding while
maintaining the original desired characteristics. In crops like
corn and soybean, a trait will be approved in one variety, and
then crossed into many other varieties, but only the first trans-
formation event requires regulatory approval. Typically, a bio-
tech submission would be for a single event produced by
inserting a gene into the genome of another plant. For exam-
ple, a Bacillus thuringiensis (Bt) gene can be inserted into a
corn variety and the event approved. Once approved for corn,
this Bt gene can be backcrossed into many commercially im-
portant corn varieties without additional regulatory approvals.
The inability to backcross potatoes results in inefficiencies
in the regulatory approval process. Because of the difficulty in
breeding, a separate transformation is needed for each variety
resulting in multiple separate approvals, one for each variety,
even though they contain the same DNA construct. All regu-
latory requirements including field studies, molecular testing,
and compositional analyses must be completed, leading to far
more time, effort, and expense than for crops where
backcrossing is feasible. This regulation by event results in
far more approvals for the commercial use of biotech traits
in multiple varieties of potatoes than in a crop like corn.
There are more than 50 commercially important potato varie-
ties (NPC 2014) that could potentially require separate trans-
formations and approvals.
The petition for deregulation of the first generation of
Innate™potatoes contained multiple events, representing dif-
ferent potato varieties. Such multi-event submissions repre-
sent significant expense for the developers and potential to
slow down the approval process within government regulato-
ry departments. In anticipation of expecting repeated submis-
sions of the same traits in multiple varieties of clonally prop-
agated crops, both the U.S. and Canada have developed
streamlined processes for approval of new events that result
from a construct that has already been approved. The USDA
has an extension process that allows for efficiencies in the
submission requirements and a shorter expected evaluation
time. In Canada, the biotech regulations are driven by consid-
eration that insertion of a trait results in a novel food. Once a
trait has been approved, it would not be considered novel. It
would be expected that the Canadian Food Inspection Agency
would have reduced requirements for new varieties trans-
formed with the same traits. Health Canada still anticipates
receiving a full safety package for the new varieties.
The Future of Biotech Potato Regulatory Clearances
The challenges of breeding potatoes while maintaining de-
sired characteristics make the use of biotechnology ideal to
take advantage of traits currently available to enhance quality
Am. J. Potato Res.

and disease resistance. A major difficulty with obtaining ap-
provals appears to be the need for replicating the requirements
in multiple potato varieties because potatoes lack the ability to
backcross. As regulatory groups become accustomed to clonal
crops, it is anticipated that other countries will streamline pro-
cesses as is occurring in the U.S. and Canada. Ideally, more
governments will accept submissions with multiple events
and streamlined evaluation when identical constructs and
traits are presented in multiple potato varieties.
New Tools for Genetic Improvement of Potato
In the past several years, new methods have been developed
for the targeted modification of plant genomes. These
methods enable precise alterations of plant DNA in vivo,
ranging from the introduction of single nucleotide substitu-
tions (Townsend et al. 2009) to the targeted insertion of
transgenes (Shukla et al. 2009). These new methods are quick-
ly changing the way plant genetic engineering is being con-
ducted and will likely affect how biotech crops are regulated
by government agencies and perceived by the public. For
example, why insert a foreign gene from a bacterium to confer
herbicide resistance when subtle alterations to native plant
genes can generate the same phenotype? Why integrate
transgenes randomly when they can now be delivered to a
specific locus where expression patterns are predictable?
Precise genome modification, or genome editing, is en-
abled by sequence-specific nucleases that create targeted chro-
mosome breaks, enabling the cell’s DNA repair pathways to
be harnessed to introduce desired sequence modifications at or
near the break site. Currently available sequence-specific nu-
cleases include zinc finger nucleases (ZFNs), homing endo-
nucleases or meganucleases, transcription activator-like effec-
tor nucleases (TALENs) and CRISPR/Cas (Puchta and Fauser
2014). In eukaryotes, the fate of a double-strand break follows
one of two pathways. In most cases, the broken chromosome
is simply rejoined, often integrating or deleting shortsegments
of DNA at the break site and potentially knocking out gene
function as part of non-homologous end-joining. In more rare
cases, homologous recombination (HR) is employed where a
homologous repair template or donor molecule is used to re-
pair the broken chromosome. The donor molecule can include
modified or additional sequence ranging from a few base pairs
to entire genes. In higher eukaryotes, such as plants, this pro-
cess is reliant on a nuclease-mediated double-strand break and
abundance of donor molecule for efficient HR to occur
(Puchta et al. 1996; Wright et al. 2005).
Genome editing tools provide a potential alternative to tra-
ditional Agrobacterium-mediated introduction of a gene of
interest. By precisely editing plant genomic DNA or targeting
the specific expression of certain genes without introducing
any permanent foreign DNA, genome editing could address
issues associated with traditional transgenics that require new
events to go through the deregulation process. TALENs have
proven their utility as reagents for genome editing in plants;
however, the TALE DNA binding domain is derived from the
bacterial plant pathogen Xanthomonas and may trigger a reg-
ulated status as codifed by USDA/APHIS regulation 7 CFR
part 340 if integrated within transgenic events being devel-
oped for commercial use.
The biotech company, Calyxt has avoided the complication
of integrating genome editing reagents by employing a tran-
sient transformation system using protoplasts to deliver
TALENs that targeted all four homologs of the potato vacuo-
lar invertase gene (VInv). Events regenerated from protoplasts
contained one to four mutated alleles that negatively correlat-
ed with reducing sugar and acrylamide content following cold
storage in the commercial variety, Ranger Russet (Clasen et al.
2015). Among these events, 39 % were negative for the
TALEN transgene and have been given non-regulated status
under the USDA as null segregates (http://www.aphis.usda.
gov/). Transient expression and use of null segregants
provides an attractive approach for utilizing genome editing
reagents to fast-track development of commercial biotech
events (Haun et al. 2014; Clasen et al. 2015).
In addition to permanent editing of the potato genome
through the use of ZFNs, TALENs, or CRISPR/Cas, other
tools for gene expression modification are just beginning to
be explored. Plant microRNAs (miRNAs) are short (20–24
nucleotides), non-coding RNA molecules important in post-
transcriptional regulation of gene expression. Hundreds of en-
dogenous plant miRNAs have been identified and can have
wide-ranging effects on plant development, abiotic and biotic
stress responses, protein turnover, and signaling through the
regulation of specific genes, many of which are transcription
factors (reviews by Zhang etal. 2006; Ruiz-Ferrer and Voinnet
2009). In potato, hundreds of miRNAs have been identified
(Zhang et al. 2009,2013;Yangetal.2010; Kim et al. 2011;
Xie et al. 2011). While the targets of potato miRNAs are
relatively easy to ascertain through sequence homology, the
effect that miRNA expression has on potato metabolism and
development is only beginning to be explored. MicroRNAs
require perfect or near-perfect complementarity to target
genes, and are therefore quite target specific. This presents
an opportunity in the future to use certain miRNAs, such as
those involved in tuber development or biotic stress responses,
to modify important traits, such as increased yield or disease
resistance.
Application of genome editing technology, such as that
available through CRISPR/Cas and TALENs, and manipula-
tion of gene expression through miRNA targeting would be a
paradigm for potato breeding and improvement efforts. Not
only would social, regulatory, and market issues be addressed
through the use of these advanced technologies (Simon 2003),
but more consistent gene expression of target genes may also
Am. J. Potato Res.

be achieved, thereby reducing the effort required to identify
high-performing biotech lines (Duan et al. 2014).
Furthermore, the use of transient expression methods to deliv-
er genome editing reagents allows modification of established
varieties without the need for further breeding and potentially
forgoes the need for regulatory clearance before commercial
release. This opens the door for the development of new po-
tato varieties developed using CRISPR/Cas or TALENs that
could be ready for field testing within the next few years,
followed by marketability within the next 8–10 years.
Agronomic Effects of Biotech Potato
Following the creation of new biotech potato cultivars, two
possible agronomic issues should be considered. The first is
the potential for pollen flow from the modified cultivars to
either weedy relatives or conventionally grown potato culti-
vars after their release into the field. Several Solanum relatives
of potato can be found as weeds in potato growing regions of
the U.S. and Canada. These include hairy nightshade
(S. physalifolium), bittersweet nightshade (S. dulcamara),
and black nightshade (S. nigrum). However, studies have
shown that these species are not sexually compatible with
cultivated potato (Eijlander and Stiekema 1994; McPartlan
and Dale 1994) and therefore the movement of biotech traits
from potato into related weeds is not likely to occur. The same
is true for the incompatibility between potato and other
Solanaceous crops, such as tomato, eggplant, and pepper.
Some wild species of potato are sexually compatible with
cultivated varieties, which could pose problems for biotech
potato grown in areas were wild species are prevalent
(Scurrah et al. 2008). In the U.S., populations of wild potato
existintheSouthwest(HijmansandSpooner2001) and have
been identified in potato growing regions, but the risk of suc-
cessful hybridization is very low (Love 1994), as there are no
reports of this happening even in intentional cross-pollination
experiments (J. Bamberg, pers. communication). Multiple re-
ports have demonstrated that movement of potato pollen over
20 m is very unlikely (Tynan et al. 1990;Dale1992;
McPartlan and Dale 1994; Conner and Dale 1996), which
suggests that the risk of pollen movement from a field con-
taining biotech potato to conventionally grown potatoes in an
adjacent field is minimal. Additionally, unlike many grain and
legume crops, the product of pollination in potato is not har-
vested and is not used for propagation of a new crop.
Volunteer potato plants, if present, are typically eliminated in
subsequent field plantings through the use of selective herbi-
cides. Consequently, with current farming practices it is highly
unlikely for introduced genes to be passed from biotech potato
cultivars to conventional ones.
A second possible consideration arises when biotech crops
contain modifications that alter the structure of the genome in
an unpredictable way. Some worry that these modifications
could have unforeseen consequences. However, if the gene
being introduced originates from a wild potato relative, then
the amount of genetic modification is actually no more than if
traditional breeding were used to introduce the gene. The bio-
tech plant will contain only the segment of DNA inserted
during transformation, while a plant developed by breeding
is expected to follow normal Mendelian genetics and contain
50 % exotic germplasm after the first cross, 25 % after the first
backcross, and so on. Finally, some biotech edited plants
would be created by knocking out the function of existing
genes, so they do not rely on the introduction of new genes.
All biotech traits are extensively tested infield and greenhouse
trials, reviewed by multiple government agencies (as
discussed above),, and demonstrated to be safe before entering
the market.
Grower and Consumer Perceptions of Biotech Potato
For a biotech potato to be a market success it mustbe accepted
by the government, producers, and consumers. The govern-
ment approval process for Simplot Innate
TM
1.0 took 2 years;
Amflora in Europe took 13 years. Many biotechnology scien-
tists and advocates claim that the regulatory process for all
biotech crops is overly burdensome and should be
streamlined.
Producer acceptance of biotechnology can be quite rapid if
the new product solves a production problem. NewLeaf
TM
potato plantings increased quickly in areas where CPB was a
problem. Even when biotech potatoes were not available, pro-
ducers were willing to use them again. In a 2010 survey of
people in the North American potato industry Toevs et al.
(2011a) found that 90 % of respondents agreed or strongly
agreed with the statement that potatoes with traits from potato
DNA will be accepted by potato growers. For transgenic po-
tatoes only 62 % agreed or strongly agreed.
BConsumer is King^is an economic principle that says
consumer preferences determine the production of goods
and services (Hutt 1937). Consumers in supermarkets, quick
service restaurants, and other places where potatoes are sold
will determine the success or failure of biotech potato prod-
ucts. Consumer research can provide insight into how the
consumers might respond to biotech potatoes entering the
market.
Hoban (1999) found that consumers in Japan and the U.S.
were optimistic about biotechnology. In both countries,
among six types of food safety risks, pesticide residues caused
the most concern and biotechnology the least. Those results
suggest a market opportunity for biotech potatoes that require
less pesticide. However, NewLeaf
TM
potatoes, though they
required less pesticide, were ultimately not accepted in the
marketplace, largely due to activist pressure on the brands of
Am. J. Potato Res.

major potato product retailers, leading to the belief that soci-
etal acceptance of new technology follows predictable pat-
terns and that more time was needed for acceptance of biotech
potatoes after their release (Guenthner 2002).
Following the market withdrawal of biotech potatoes, some
researchers included potato products in their consumer
biotech-acceptance studies. In one, 86 % of Canadian con-
sumers said that they would be willing to pay a price premium
for Bheart-healthy^biotech potato chips (West et al. 2002).
Others found that consumers would pay higher prices for po-
tato chips labeled as GM-free (VanWechel et al. 2003).
Consumers given more information, whether negative or pos-
itive about biotech, increased the price they would pay for
chips presumed to have been made with biotech potatoes.
Loureiro and Hine (2002) studied consumer willingness-
to-pay for three types of fresh potatoes: organic, local, and
GM-free. They were willing to pay the highest premium for
locally produced potatoes and the lowest premium for GM-
free potatoes. Huffman (2003) conducted experimental auc-
tions for three food products –vegetable oil, tortilla chips, and
fresh russet potatoes, and found that consumers were willing
to pay more for biotech-free products. Information from envi-
ronmental groups reduced the amount consumers would pay
for biotech potato, but those differences disappeared when
participants were given verifiable, third-party information that
disputed the environmental groups’claims (Huffman et al.
2004). Rousu et al. (2003) found that participants would pay
less for potatoes that contained some biotech content, but that
there was no difference in values between products with 1 and
5 % tolerance level for biotech content.
Lusk and Sullivan (2002) asked consumers about willing-
ness to eat a vegetable transformed with seven different types
of genes. At the low end, acceptance for using genes from a
virus, fungus, bacteria, or animal ranged from 14 to 23 %. At
the high end, 81 % would accept a product that used genes
from the same vegetable.
NewLeaf
TM
potatoes were prematurely cited as a success
story for effective biotech marketing (Phillips and Corkindale
2002). In 1999 Monsanto began a marketing campaign in
Prince Edward Island (PEI), where pesticides applied to potato
fields had leached into rivers and coastal waters, resulting in
fish kills. Focusing on the reduction of insecticide use for
NewLeaf
TM
potatoes, Monsanto proactively marketed their
biotech fresh potatoes as an environmentally friendly product.
They made biotech fresh potatoes available in PEI grocery
stores and used advertising, publicity, point-of-sale informa-
tion, and a toll-free phone line as marketing tools. Even with
premium prices, the entire crop of biotech fresh potatoes
quickly sold out. The next year a major potato processor and
a buyer of PEI potatoes announced that they would stop buy-
ing biotech potatoes because of perceived consumer resis-
tance. Although biotech potatoes were successful in the fresh
market, the lack of support in the processing industry
contributed to the withdrawal of biotech potatoes from the
entire North American market.
Future market acceptance of biotech potato will be
influenced by the type of biotechnology used to develop
new products. Anti-GM activists often define GM as
transferring DNA from one species to another. Since
techniques like gene editing may not fit that definition,
non-government organizations that are outspoken oppo-
nents of transgenics may be open to support of other
types of biotech potatoes. Simplot’s Innate
TM
potatoes
with traits introduced from potato DNA will soon test
that hypothesis in the North American market. Perhaps
others may soon begin testing in Europe: the Dutch gov-
ernment recently made a commitment to provide 10 mil-
lion euros per year to a public/private research group for
tomato and potato breeding. That investment could have
come about only with some optimism that non-transgenic
biotechnology will be treated favorably in the EU regu-
latory system.
Gene-editing and biotechnology using traits from the same
species could alter the discussions regarding labeling of food
products derived from biotech crops. Debates about biotech
labeling typically include a focus on the breeding tool rather
than the product. If labeling of products derived from biotech
crops becomes mandatory, this could simply provide an op-
portunity to publicize the benefits of biotech potatoes. The
current US system of voluntary labeling that allows food man-
ufacturers to use GM-Free labels could also help bring price
premiums to labeled biotech potatoes that have traits popular
with consumers. One way to help that happen could be to use
different terminology on labels. Unfortunately, the terms GM
and GMO have become pejoratives in the popular press. For
consumer acceptance purposes, less disparaging terms, such
as ‘biotech’or ‘genetically enhanced’, could replace GM
while still conveying the intended meaning.
At the time of the writing of this review article, the
U.S. congress is in the process of discussing the Safe
and Accurate Food Labeling Act. This bill amends the
Federal Food, Drug, and Cosmetic Act to require the
Food and Drug Administration (FDA) to continue the
voluntary consultation process established under the
FDA to evaluate a scientific and regulatory assessment
provided by the biotech food developer.
The FDA may require a biotech food to have a label that
informs consumers of any material difference between the
biotech food and a comparable food. But, the use of biotech-
nology to develop food does not, by itself, constitute a mate-
rial difference, and biotech food developers may voluntarily
disclose how a product has been genetically engineered, but
they are not required to do so under the bill. The bill also will
preempt state and local restrictions on GMO food and labeling
requirements, which have appeared in several locations
throughout the U.S.
Am. J. Potato Res.

Benefits of Biotech Potato
NatureMark potatoes provided benefits to farmers, processors,
consumers, and the environment. Growers who planted
NewLeaf™potatoes reduced insecticide expenditures and in-
creased revenue due to higher yields and better quality.
According to Kaniewski and Thomas (2004), Idaho growers
saved $350 per hectare on their NewLeaf Plus
TM
plantings
and growers in the Columbia Basin saved $405 per hectare.
Processors benefitted from a higher quality raw product free of
net necrosis (internal discoloring). Consumers enjoyed higher
quality potato products at no increase in costs.
The environment benefitted because nearly two million
pounds of insecticides and 30,000 spray plane sorties were
not needed on the NewLeaf
TM
fields in the Pacific
Northwest (Kaniewski and Thomas 2004). For the whole
U.S. potato crop, the NewLeaf
TM
potatoes could significantly
reduce the 2.6 million pounds of pesticides applied each year
(Phipps and Park 2002; Brookes and Barfoot 2005). Other
researchers confirmed that biotech potatoes could decrease
pesticide use and increase grower profits (Marra et al. 2002;
Flannery et al. 2004).
Less pesticide use and reduced crop losses through biotech-
nology also appeal to potato growers in developing countries
(Curtis et al. 2004; Huesing and English 2004). Biotech pota-
toes developed at Michigan State University were field tested
in South Africa and Egypt and found to control Potato Tuber
Moth (PTM), a pest that can cause severe losses in yield and
quality. Researchers found the PTM-resistant potatoes could
increase food security, reduce food prices, increase farm prof-
itability, and protect the environment in those two countries
(Guenthner et al. 2004). Growers in South Africa could save
the costs of applying nine different insecticides that are typi-
cally used to control PTM. Resource-poor farmers who cannot
afford pesticides would benefit from better yields and quality.
Some of the economic and environmental benefits of
potatoes with late blight resistance, low acrylamide po-
tential, reduced black spot, and lowered reducing sugars
potatoes were estimated by Guenthner (unpublished
2015). In addition to these traits, benefits include re-
duced potato waste, better fresh pack-out and increased
grower profits. Estimates of the impacts of the black
spot bruise, blight, and storage traits are shown in
Tab le 1and discussed below.
Fresh Potato Black Spot Bruise We estimated impacts on
U.S. fresh potato growers, packers, retailers and foodservice if
all fresh potatoes (24 % of the U.S. crop) had the black spot
bruise resistant trait. Interviews with fresh potato experts pro-
vided estimates of the amount of waste due to black spot
bruise that would be reduced with this trait. Using 2013 crop
data, we estimated that 1.9 million metric tonnes (mmt) of
potatoes would not be lost. At the 2013 average potato yield,
that meant that 8,600 fewer hectares would need to be planted
to produce the same size crop. This translates to 145,000 hect-
ares of potato that would no longer require pesticide applica-
tions. Using metrics from Field to Market (2015), we estimat-
ed that 0.3 mmt pounds of CO
2
and 55 billion liters of water
would be saved.
Late Blight We also estimated potential impacts of late blight
resistance for the entire U.S. potato industry. Expert opinion
research provided data on potential fungicide reduction due to
the late blight resistance trait. Research by Guenthner et al.
(2001) provided estimates of reduced late blight yield loss
(5 %) and storage loss (1.7 %). We estimated that 6.4 mmt
of waste and yield loss would be reduced, the equivalent of 28,
900 hectares. Potato pesticide hectare-applications would be
reduced by 492,000. Using Field to Market metrics, we esti-
mated a savings of 1.0 mmt of CO
2
emissions and 186 billion
liters of water. Actual savings will depend on regulatory clear-
ance and adoption of late blight resistant varieties.
Processed Potato Storage We estimated impacts of cold stor-
age on the U.S. potato crop that goes into processing. USDA
data revealed that 89 % of the U.S. potato crop was harvested
in the fall. Using USDA monthly sales data we estimated that
81 % of the fall crop is stored. Research by Patterson (2013)
provided information on Chlorpropham (CIPC) application
timing and costs. Research by Sparks and Summers (1974)
was the source of data for cold storage savings in potato shrink
and loss for each month of storage. We estimated that 2.6 mmt
of potatoes would not be lost if all stored processed potatoes
had the cold storage trait. The reduced waste is the amount that
could be grown on 11,300 hectares. Pesticide application
would decline by 370,000 hectare-applications. CO
2
emis-
sions would decline by 0.4 mmt and water use would drop
by 76 billion liters. A large, but undetermined share of those
benefits would come from Russet Burbank, the dominant va-
riety in frozen processing.
Costs We estimated the economic impact of potato varieties
with late blight resistance, low acrylamide potential, reduced
black spot, and lowered reducing sugars, on production costs
for typical Eastern Idaho russet potato growers. Operating
costs per hectare, excluding any changes in seed potato costs,
could be expected to decline 12 %. Due to higher marketable
yields and less waste, operating costs per tonne would go
down 28 %.
Alternate Crops This analysis involved estimates of potato
hectares not planted. Due to reduced shrink, loss and waste,
reduced plantings could produce the same total quantity. The
above estimates do not account for the crops that growers
would plant instead of potatoes. Since small grains is a com-
mon rotation crop for many potatoes growers, it is likely that
Am. J. Potato Res.

some plantings would shift from potatoes to grain. For each
hectare shifted to small grains by typical Eastern Idaho potato
growers, production costs go down an estimated $3,900, and
CO
2
emissions would decrease 56 %.
Directed Marketing Stewardship Although we did not
attempt to estimate its value, enhanced stewardship is
an additional benefit that with the introduction of bio-
tech into potato markets. One of the unrecognized needs
for NatureMark
TM
potatoes was a directed marketing
approach to guide the flow of biotech product into
intended markets and away from international market
channels. Simplot has developed a closed loop system
to reduce that risk, pending completion of international
approvals. Described as a risk-based system that directs
potatoes to intended markets, the program restricts han-
dling of Innate
TM
potatoes to licensed growers, packers,
processors, and distributors. Within the program is a list
of production practices, including such things as equip-
ment clean-out and cull disposal for the licensees in the
Innate
TM
supply chain. From an analysis of certified
seed potato variety purity, Guenthner et al. (2012)con-
cluded that if commercial growers used identity preser-
vation production practices employed by seed potato
growers, biotech potato content could be well within
Japan’s expected import tolerance of 5 % biotech to
trigger labeling requirements, once events are approved
in Japan.
Future Prospects
The mass selection breeding method used by many po-
tato breeders has changed little over the past century.
Despite this, the overall yield of potato crops in the
U.S. has steadily increased. The average yield of pota-
toes in 2014 was 426 cwt/acre compared to 66 cwt/acre
in 1930, an increase of 630 % (NASS 2015). The expan-
sion of genomic resources for potato and the application
of these resources towards the improvement of new va-
rieties and germplasm has been an area of intensive
study over the past 20 years. While increased yield re-
mains a primary focus for most breeders, the develop-
ment of potato that requires fewer inputs and possesses
wider environmental adaptability will allow the crop to
continue to grow as a significant and nutritional food
source worldwide. Biotechnology provides reliable and
rapid methods for the incorporation of traits (genes) that
are realized through the use of expanding genomic re-
sources. Potato was one of the first crops to be geneti-
cally modified, and it remains at the forefront of biotech-
nology research due in part to its rapid regeneration and
resilience after being subjected to tissue culture. As new
tools are developed for efficient and specific editing of
the potato genome, more complex challenges can be
approached, leading to continued crop improvement and
scientific achievements.
The apparent impacts that biotech potato could have
on enhanced nutrition, reduced pesticide applications,
and decreased food waste, have been perceived positive-
ly by consumers in the U.S. These perceptions can dif-
fer widely in other parts of the world, and have led to
the expansion of biotech potato development in some
areas and elimination in others. A continued focus on
improvements that directly benefit consumers will be
importanttotheviabilityofbiotechpotatointhemar-
ketplace. In addition to agronomic and nutrition benefits
described in this review, non-food applications of bio-
tech potato for industrial, pharmaceutical, and veterinary
purposes could also benefit consumers through de-
creased manufacturing costs and increased functionality
of therapeutic molecules (review by Rigano et al. 2013)
or starch-derived polymers (Neumann et al. 2005;
Hühns et al. 2009). As research continues to identify
and address challenges associated with potato produc-
tion, we predict a corresponding invention of products
that will advance the industry. With the help of biotech-
nology, we hope that science will continue to provide
increased value and quality of potato products without
changing consumer’s perceptions of the Bhumble spud^
that is so well recognized and welcomed at dinner ta-
bles throughout the world.
Tabl e 1 Estimated economic and
sustainability benefits of potatoes
with late blight resistance, low
acrylamide potential, reduced
black spot, and lowered reducing
sugars
Item Bruise Blight Storage Total
Market Fresh All Processed N/A
Potato waste reduced (million metric tonnes) 1.9 6.4 2.6 10.9
CO
2
emissions reduced (million metric tonnes) 0.3 1.0 0.4 1.6
Water use reduced (billion liters) 55 186 76 316
Pesticide applications reduced (hectares) 145,000 492,000 370,000 1,007,000
Potato plantings not needed (hectares) 8,600 28,900 11,300 48,800
Costs of production saved (million US$) $42 $141 $55 $238
Am. J. Potato Res.

Acknowledgments Salary funding for N. Butler was provided by
USDA Biotechnology Risk Assessment Grant number 2013-33522-
21090.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give appro-
priate credit to the original author(s) and the source, provide a link to the
Creative Commons license, and indicate if changes were made.
References
Bachem, C.W.B., G.-J. Speckmann, P.C.G. van der Linde, F.T.M.
Verheggen, M.D. Hunt, J.C. Steffens, and M. Zabeau. 1994.
Antisense expression of polyphenol oxidase genes inhibits enzymat-
ic browning in potato tubers. Nature Biotechnology 12: 1101–1105.
Ballvora, A., M.R. Ercolano, J. Weiss, K. Meksem, C.A. Bormann, P.
Oberhagemann, F. Salamini, and C. Gebhardt. 2002. The R1 gene
for potato resistance to late blight (Phytophthora infestans)belongs
to the leucine zipper/NBS/LRR class of plant resistance genes.Plant
Journal 30: 361–371.
BASF. 2013. BASF to expand its plant biotechnology research into fun-
gal resistance in corn.
Baum, J.A., T. Bogaert, W. Clinton, G.R. Heck, P. Feldmann, O. Ilagan,
S. Johnson,G. Plaetinck, T. Munyikwa, M. Pleau, T. Vaughn, and J.
Roberts. 2007. Control of coleopteran insect pests through RNA
interference. Nature Biotechnology 25: 1322–1326.
Becalski, A., B.P. Lau, D. Lewis, and S.W. Seaman. 2003. Acrylamide in
foods: occurrence, sources, and modeling. Journal of Agricultural
and Food Chemistry 51: 802–808.
Bendahmane, M., J.H. Fitchen, G.M. Zhang, and R.N. Beachy. 1997.
Studies of coat protein-mediated resistance to tobacco mosaic
tobamovirus: correlation between assembly of mutant coat proteins
and resistance. Journal of Virology 71: 7942–7950.
Bendahmane, A., M. Querci, K. Kanyuka, and D.C. Baulcombe. 2000.
Agrobacterium transient expression system as a tool for the isolation
of disease resistance genes: application to the Rx2 locus in potato.
Plant Journal 21: 73–81.
Benzing-Purdie, L.M., J.A. Ripmeester, and C.I. Ratcliffe. 1985. Effects
of temperature on Maillard reaction products. Journal of
Agricultural and Food Chemistry 33: 31–33.
Bhaskar, P.B., L. Wu, J.S. Busse, B.R. Whitty, A.J. Hamernik, S.H.
Jansky, C.R. Buell, P.C. Bethke, and J. Jiang. 2010. Suppression
of the vacuolar invertase gene prevents cold-induced sweetening
in potato. Plant Physiology 154: 939–948.
Bouwmeester, K., M. Han, R. Blanco-Portales, W. Song, R. Weide, L.-Y.
Guo, E.A.G. van der Vossen, and F. Govers. 2014. The Arabidopsis
lectin receptor kinase LecRK-I.9 enhances resistance to
Phytophthora infestans in Solanaceous plants. Plant
Biotechnology Journal 12: 10–16.
Brookes, G., and P. Barfoot. 2005. GM crops: the global socio-economic
and environmental impact –the first nine years 1996–2004.
Brown, C.R., C.G. Edwards, C.-P. Yang, and B.B. Dean. 1993. Orange
flesh trait in potato: Inheritance and carotenoid content. Journal of
the American Society for Horticultural Science 118: 145–150.
Bulley, S., M. Wright, C. Rommens, H. Yan, M. Rassam, K. Lin-Wang,
C. Andre, D. Brewster, S. Karunairetnam, A.C. Allan, and W.A.
Laing. 2012. Enhancing ascorbate in fruits and tubers through
over-expression of the L-galactose pathway gene GDP-L-galactose
phosphorylase. Plant Biotechnology Journal 10: 390–397.
Bushey, D.F., G.A. Bannon, B.F. Delaney, G. Graser, M. Hefford, X.
Jiang, T.C. Lee, K.M. Madduri, M. Pariza, L.S. Privalle, R.
Ranjan, G. Saab-Rincon, B.W. Schafer, J.J. Thelen, J.X. Zhang,
and M.S. Harper. 2014. Characteristics and safety assessment of
intractable proteins in genetically modified crops. Regulatory
Toxicology and Pharmacology 69: 154–170.
Cabello, R., F. De Mendiburu, M. Bonierbale, P. Monneveux, W. Roca,
and E. Chujoy. 2012. Large-scale evaluation of potato improved
varieties, genetic stocks and landraces for drought tolerance.
AmericanJournalofPotatoResearch89: 400–410.
Cavatorta, J., K.W. Perez, S.M. Gray, J. Van Eck, I. Yeam, and M. Jahn.
2011. Engineering virus resistance using a modified potato gene.
Plant Biotechnology Journal 9: 1014–1021.
Chakravarty, B., G. Wang-Pruski, B. Flinn, V. Gustafson, and S. Regan.
2007. Genetic transformation in potato: approaches and strategies.
AmericanJournalofPotatoResearch84: 301–311.
Chawla, R., R. Shakya, and C.M. Rommens. 2012. Tuber-specific silenc-
ing of asparagine synthetase-1 reduces the acrylamide-forming po-
tential of potatoes grown in the field without affecting tuber shape
and yield. Plant Biotechnology Journal 10: 913–924.
Chi, M., B. Bhagwat, W.D. Lane, G. Tang, Y. Su, R. Sun, B.D. Oomah,
P.A. Wiersma, and Y. Xiang. 2014. Reduced polyphenol oxidase
gene expression and enzymatic browning in potato (Solanum
tuberosum L.) with artificial microRNAs. BMC Plant Biology 14:
62.
Clasen, B.M., T.J. Stoddard, S. Luo, Z.L. Demorest, J. Li, F. Cedrone, R.
Tibebu, S. Davison, E.E. Ray, A. Daulhac, A. Coffman, A.
Yabandith, A. Retterath, W. Haun, N.J. Baltes, L. Mathis, D.F.
Voytas, and F. Zhang. 2015. Improving cold storage and processing
traits in potato through targeted gene knockout. Plant Biotechnology
Journal.doi:10.1111/pbi.12370.
Coetzer, C., D. Corsini, S. Love, J. Pavek, and N. Tumer. 2001. Control of
enzymatic browning in potato (Solanum tuberosum L.) by sense and
antisense RNA from tomato polyphenol oxidase. Journal of
Agricultural and Food Chemistry 49: 652–657.
Conner, A.J., and P.J. Dale. 1996. Reconsideration of pollen dispersal
data from field trials of transgenic potatoes. Theoretical and
Applied Genetics 92: 505–508.
Curtis, K., J. McCluskey, and T. Wahl. 2004. Consumer acceptance of
genetically modified food products in the developing world.
AgBioforum 7: 70–75.
Dale, P.J. 1992. Spread of engineered genes to wild relatives. Plant
Physiology 100: 13–15.
Du, J., E. Verzaux, A. Chaparro-Garcia, G. Bijsterbosch, L.C.P. Keizer, J.
Zhou, T.W.H. Liebrand, C. Xie, F. Govers,S. Robatzek, E.A.G. van
der Vossen, E. Jacobsen, R.G.F. Visser, S. Kamoun and V.G.A.A.
Vleeshouwers. 2015. Elicitin recognition confers enhanced resis-
tance to Phytophthora infestans in potato. Nature Plants 1.
Duan, H., C. Richael, and C. Rommens. 2012. Overexpression of the
wild potato eIF4E-1variant Eva1 elicits Potato virus Y resistance
in plants silenced for native eIF4E-1. Transgenic Research 21: 929–
938.
Duan, H., A. Forsyth, T. Weeks and C. Richael. 2014. TAL-mediated
targeted DNA integration in potato plants. 98th Annual Meeting
of the Potato Association of America.
Eijlander, R., and W. Stiekema. 1994. Biological containment of potato
(Solanum tuberosum): outcrossing to the related wild species black
nightshade (Solanum nigrum) and bittersweet (Solanum
dulcamara). Sexual Plant Reproduction 7: 29–40.
Fairbairn, D.J., A.S. Cavallaro, M. Bernard, J. Mahalinga-Iyer, M.W.
Graham, and J.R. Botella. 2007. Host-delivered RNAi: an effective
strategy to silence genes in plant parasitic nematodes. Planta 226:
1525–1533.
FDA. 2015. http://www.accessdata.fda.gov/scripts/fdcc/?set=Biocon.
Accessed 15 May 2015.
Field to Market. 2015. Fieldprint calculator. https://www.fieldtomarket.org/.
Accessed 22 May 2015.
Am. J. Potato Res.

Flannery, M., F. Thorne, P. Kelley, and E. Mullins. 2004. An economic
cost-benefit analysis of GM crop cultivation: and Irish case study.
AgBioforum 7: 149–157.
Foster, S.J., T.-H. Park, M. Pel, G. Brigneti, J. Śliwka, L. Jagger, E. van
der Vossen, and J.D.G. Jones. 2009. Rpi-vnt1.1,aTm-22 homolog
from Solanum venturii, confers resistance to potato late blight.
Molecular Plant-Microbe Interactions 22: 589–600.
Fradin, E.F., Z. Zhang, J.C. Juarez Ayala, C.D.M. Castroverde, R.N.
Nazar, J. Robb, C.-M. Liu, and B.P.H.J. Thomma. 2009. Genetic
dissection of Verticillium wilt resistance mediated by tomato Ve1 .
Plant Physiology 150: 320–332.
Gao, Z., E. Johansen, S. Eyers, C.L. Thomas, T.H. Noel Ellis, and A.J.
Maule. 2004. The potyvirus recessive resistance gene, sbm1, iden-
tifies a novel role for translation initiation factor eIF4E in cell-to-cell
trafficking. The Plant Journal 40: 376–385.
Ghag, S.B., U.K. Shekhawat, and T.R. Ganapathi. 2014. Host-induced
post-transcriptional hairpin RNA-mediated gene silencing of vital
fungal genes confers efficient resistance against Fusarium wilt in
banana. Plant Biotechnology Journal 12: 541–553.
Goldbach, R., E. Bucher, and M. Prins. 2003. Resistance mechanisms to
plant viruses: an overview. Virus Research 92: 207–212.
Gonsalves, D. 1998. Control of papaya ringspot virus in papaya: a case
study. Annual Review of Phytopathology 36: 415–437.
Gonsalves, D., C. Gonsalves, S. Ferreira, K. Pitz, M. Fitch, R. Manshardt,
and J. Slightom. 2004. Transgenic virus resistant papaya: from hope
to reality for controlling Papaya ringspot virus in Hawaii. APSnet
Features.doi:10.1094/APSnetFeature-2004-0704.
Govindarajulu, M., L. Epstein, T. Wroblewski and R.W. Michelmore.
2014. Host-induced gene silencing inhibits the biotrophic pathogen
causing downy mildew of lettuce. Plant Biotechnology Journal.
Gregory, P., S.L. Sinden, S.F. Osman, W.M. Tingey, and D.A. Chessin.
1981. Glycoalkaloids of wild, tuber-bearing Solanum species.
Journal of Agricultural and Food Chemistry 29: 1212–1215.
Guenthner, J. 2001. The international potato industry. Woodhead
Publishing, Cambridge UK.
Guenthner, J. 2002. Consumer acceptance of genetically modified pota-
toes. AmericanJournalofPotatoResearch79: 309–315.
Guenthner, J., K. Michael, and P. Nolte. 2001. Potato late blight’simpact
on growers. Potato Research 44: 121–125.
Guenthner, J., A. Araji, and K. Maredia. 2004. Benefits of public invest-
ment in potato biotechnology for developing countries. Applied
Biotechnology, Food Science and Policy 1: 235–242.
Guenthner, J.F., A.J. Johnson, and C.S. McIntosh. 2012. Seed variety
mix: an indicator for GM potato identity preservation. American
Journal of Potato Research 89: 172–174.
Hamilton, C.M., A. Frary, C. Lewis, and S.D. Tanksley. 1996. Stable
transfer of intact high molecular weight DNA into plant chromo-
somes. Proceedings of the National Academy of Sciences 93: 9975–
9979.
Hamilton,J.P., C.N. Hansey, B.R. Whitty, K. Stoffel, A.N. Massa, A. Van
Deynze, W.S. De Jong, D.S. Douches, and C.R. Buell. 2011. Single
nucleotide polymorphism discovery in elite north american potato
germplasm. BMC Genomics 12: 302–313.
Hanneman Jr., R.E. 1989. The potato germplasm resource. The American
Potato Journal 66: 655–667.
Haun, W., A. Coffman, B.M. Clasen, Z.L. Demorest, A. Lowy, E. Ray, A.
Retterath, T. Stoddard, A. Juillerat, F. Cedrone, L. Mathis, D.F.
Voytas, and F. Zhang. 2014. Improved soybean oil quality by
targeted mutagenesis of the fatty acid desaturase 2 gene family.
Plant Biotechnology Journal 12: 934–940.
Hemavathi, C., N. Upadhyaya, K. Akula, S. Young, D. Kim Chun, and S.
Park. 2010. Enhanced ascorbic acid accumulation in transgenic po-
tato confers tolerance to various abiotic stresses. Biotechnology
Letters 32: 321–330.
Hijmans, R.J., and D.M. Spooner. 2001. Geographic distribution of wild
potato species. American Journal of Botany 88: 2101–2112.
Hirsch, C.N., C.D. Hirsch, K. Felcher, J. Coombs, D. Zarka, A. van
Deynze, W. de Jong, R. Veilleux, S. Jansky, P. Bethke, D.S.
Douches, and C.R. Buell. 2013. Retrospective view of North
American potato (Solanum tuberosum L.) breeding in the 20th and
21st centuries. G3: Genes, Genomes, Genetics 3:1003–1013.
Hoban, T. 1999. Consumer acceptance of biotechnology in the United
States and Japan. Food Technology 53: 50–54.
Huang, S., E.A.G. van der Vossen, H. Kuang, V.G.A.A. Vleeshouwers,
N. Zhang, T.J.A. Borm, H.J. van Eck, B. Baker, E. Jacobsen, and
R.G.F. Visser. 2005. Comparative genomics enabled the isolation of
the R3a late blight resistance gene in potato. The Plant Journal 42:
251–261.
Huang, G., R. Allen, E.L. Davis, T.J. Baum, and R.S. Hussey. 2006.
Engineering broad root-knot resistance in transgenic plants by
RNAi silencing of a conserved and essential root-knot nematode
parasitism gene. Proceedings of the National Academy of Sciences
oftheUnitedStatesofAmerica103: 14302–14306.
Huesing, J., and L. English. 2004. The impact of Bt crops on the devel-
oping world. AgBioforum 7: 84–95.
Huffman, W. 2003. Consumers’acceptance of (and resistance to) genet-
ically modified foods in high-income countries: effects of labels and
information in an uncertain environment. American Journal of
Agricultural Economics 85: 1112–1118.
Huffman, W., J. Shogren, M. Rousu, and A. Tegene. 2004. Consumer
willingness to pay for genetically modified food labels in a market
with diverse information: evidence from experimental auctions.
Journal of Agricultural and Resource Economics 28: 481–502.
Hühns, M., K. Neumann, T. Hausmann, F. Klemke, W. Lockau, U.
Kahmann, L. Kopertekh, D. Staiger, E.K. Pistorius, J. Reuther, E.
Waldvogel, W. Wohlleben, M. Effmert, H. Junghans, K. Neubauer,
U. Kragl, K. Schmidt, J. Schmidtke, and I. Broer. 2009. Tuber-
specific cphA expression to enhance cyanophycin production in po-
tatoes. Plant Biotechnology Journal 7: 883–898.
Hutt, W. 1937. Economists and the Public.
Huvenne, H., and G. Smagghe. 2010. Mechanisms of dsRNA uptake in
insects and potential of RNAi for pest control: a review. Journal of
Insect Physiology 56: 227–235.
Ibiza, V., J. Canizares, and F. Nuez. 2010. EcoTILLING in Capsicum
species: searching for new virus resistances. BMC Genomics 11:
631.
ISAAA. 2015. Potato (Solanum tuberosum L.) GM events. http://www.
isaaa.org/gmapprovaldatabase/crop/default.asp?CropID=
16&Crop=Potato. Accessed 22 May 2015.
Jahan, S.N., A.K. Asman, P. Corcoran, J. Fogelqvist, R.R. Vetukuri, and
C. Dixelius. 2015. Plant-mediated gene silencing restricts growth of
the potato late blight pathogen Phytophthora infestans. Journal of
Experimental Botany 66: 2785–2794.
James, C. 2014. Global status of commercialized biotech/GM crops.
ISAAA Brief No. 49–2014.
Jansky, S. 2000. Breeding for disease resistance in potato. Plant Breeding
Reviews 19: 69–155.
Jones, D.A., C.M. Thomas, K.E. Hammond-Kosack, P.J. Balint-Kurti,
and J.D. Jones. 1994. Isolation of the tomato Cf-9gene for resistance
to Cladosporium fulvum by transposon tagging. Science 266: 789–
793.
Jones, J., S.J. Foster, Z. Chu, T.-H. Park, V.D.V.E.A. G, M.A. Pel and
R.G.F. Visser. 2009. Late blight resistance genes and methods.
Kang, B.-C., I. Yeam, J.D. Frantz, J.F. Murphy, and M.M. Jahn. 2005.
The pvr1 locus in Capsicum encodes a translation initiation factor
eIF4E that interacts with tobacco etch virus VPg. The Plant Journal
42: 392–405.
Kang, B.C., I. Yeam, H.X. Li, K.W. Perez, and M.M. Jahn. 2007.Ectopic
expression of a recessive resistance gene generates dominant
potyvirus resistance in plants. Plant Biotechnology Journal 5:
526–536.
Am. J. Potato Res.

Kaniewski, W., and P. Thomas. 2004. The potato story. AgBioforum 7:
41–46.
Kanyuka, K., A. Druka, D.G. Caldwell, A. Tymon, N. McCallum, R.
Waugh, and M.J. Adams. 2005. Evidence that the recessive
bymovirus resistance locus rym4 in barley corresponds to the eu-
karyotic translation initiation factor 4E gene. Molecular Plant
Pathology 6: 449–458.
Kawchuk,L.M.,J.Hachey,D.R.Lynch,F.Kulcsar,G.van
Rooijen, D.R. Waterer, A. Robertson, E. Kokko, R. Byers,
R.J.Howard,R.Fischer,andD.Prufer.2001.TomatoVe
disease resistance genes encode cell surface-like receptors.
Proceedings of the National Academy of Sciences of the
United States of America 98: 6511–6515.
Kierzkowski,D.,M.Kmieciak,P.Piontek,P.Wojtaszek,Z.
Szweykowska-Kulinska, and A. Jarmolowski. 2009. The
Arabidopsis CBP20 targets the cap-binding complex to the nucleus,
and is stabilized by CBP80. The Plant Journal 59: 814–825.
Kim,H.J.,K.H.Baek,B.W.Lee,D.Choi,andC.G.Hur.2011.
In silico identification and characterization of microRNAs
and their putative target genes in Solanaceae plants.
Genome 54: 91–98.
Koch, A., N. Kumar, L. Weber, H. Keller, J. Imani, and K.H. Kogel.
2013. Host-induced gene silencing of cytochrome P450 lanosterol
C14alpha-demethylase-encoding genes confers strong resistance to
Fusarium species. Proceedings of the National Academy of Sciences
oftheUnitedStatesofAmerica110: 19324–19329.
Lacombe, S., A. Rougon-Cardoso, E. Sherwood, N. Peeters, D.
Dahlbeck,H.P.vanEsse,M.Smoker,G.Rallapalli,B.P.H.J.
Thomma, B. Staskawicz, J.D.G. Jones, and C. Zipfel. 2010.
Interfamily transfer of a plant pattern-recognition receptor confers
broad-spectrum bacterial resistance. Nature Biotechnology 28: 365–
369.
Liu, Z., and D. Halterman. 2006. Identification and characterization of RB
orthologous genes from the late blight resistant wild potato species
Solanum verrucosum. Physiological and Molecular Plant
Pathology 69: 230–239.
Lokossou, A.A., T.-h. Park, G. van Arkel, M. Arens, C. Ruyter-Spira, J.
Morales, S.C. Whisson, P.R.J. Birch, R.G.F. Visser, E. Jacobsen, and
E.A.G. van der Vossen. 2009. Exploiting knowledge of R/Avr genes
to rapidly clone a new LZ-NBS-LRR family oflate blight resistance
genes from potato linkage group IV. Molecular Plant-Microbe
Interactions 22: 630–641.
Loureiro, M. and S. Hine. 2002. Discovering niche markets: a compari-
son of consumer willingness to pay for local, organic and GMO-free
products. Journal of Agricultural and Applied Economics 34.
Love, S. 1994. Ecological risk of growing transgenic potatoes in the
United States and Canada. American Potato Journal 71: 647–658.
Lusk, J., andP. Sullivan. 2002. Consumer acceptance of genetically mod-
ified foods. Food Technology 56: 32–37.
Mackerron, D.K.L., and R.A. Jefferies. 1988. The distributions of tuber
sizes in droughted and irrigated crops of potato. I. Observations on
the effect of water stress on graded yields from differing cultivars.
Potato Research 31: 269–278.
Marra, M., P. Pardey, and J. Alston. 2002. The payoffs to transgenic field
crops: an assessment of the evidence. AgBioforum 5: 43–50.
McCue, K.F., L.V.T. Shepherd, P.V. Allen, M.M. Maccree, D.R.
Rockhold, D.L. Corsini, H.V. Davies, and W.R. Belknap.
2005. Metabolic compensation of steroidal glycoalkaloid bio-
synthesis in transgenic potato tubers: using reverse genetics
to confirm the in vivo enzyme function of a steroidal alka-
loid galactosyltransferase. Plant Science 168: 267–273.
McDougall, P. 2011. The cost and time involved in the discovery, devel-
opment and authorisation of a new plant biotechnology derived trait.
A Consultancy Study for Crop Life International.
McKenzie, M.J., R.K. Chen, J.C. Harris, M.J. Ashworth, and D.A.
Brummell. 2013. Post-translational regulation of acid invertase
activity by vacuolar invertase inhibitor affects resistance to cold-
induced sweetening of potato tubers. Plant, Cell & Environment
36: 176–185.
McPartlan, H., and P. Dale. 1994. An assessment of gene transfer by
pollen from field-grown transgenic potatoes to non-transgenic pota-
toes and related species. Transgenic Research 3: 216–225.
Michelmore, R.W., and B.C. Meyers. 1998. Clusters of resistance genes
in plants evolve by divergent selection and a birth-and-death pro-
cess. Genome Research 8: 1113–1130.
Miller, J., and K. Bradford. 2010. The regulatory bottleneck for biotech
specialty crops. Nature Biotechnology 28: 1012–1014.
Monneveux, P., D.A. Ramirez, and M.T. Pino.2013. Drought tolerance in
potato (S. tuberosum L.): can we learn from drought tolerance re-
search in cereals? Plant Science 205–206: 76–86.
Naderpour, M., O.L.E.S. Lund, R. Larsen, and E. Johansen. 2010.
Potyviral resistance derived from cultivars of Phaseolus vulgaris
carrying bc-3is associated with the homozygotic presence of a mu-
tated eIF4E allele. Molecular Plant Pathology 11: 255–263.
NASS. 2015. National Agricultural Statistics Service. http://www.nass.usda.
gov/Statistics_by_Subject/index.php?sector=CROPS. Accessed 15
May 2015.
National Toxicology Program. 2011. Report on Carcinogens, Twelfth
Edition. http://ntp.niehs.nih.gov/ntp/roc/twelfth/profiles/
Acrylamide.pdf. Accessed 15 May 2015.
Neumann, K., D.P. Stephan, K. Ziegler, M. Huhns, I. Broer, W. Lockau,
and E.K. Pistorius. 2005. Production of cyanophycin, a suitable
source for the biodegradable polymer polyaspartate, in transgenic
plants. Plant Biotechnology Journal 3: 249–258.
Nicaise, V., S. German-Retana, R. Sanjuán,M.-P. Dubrana, M. Mazier, B.
Maisonneuve, T. Candresse, C. Caranta, and O. LeGall. 2003. The
eukaryotic translation initiation factor 4E controls lettuce suscepti-
bility to the potyvirus lettuce mosaic virus. Plant Physiology 132:
1272–1282.
Nieto, C., M. Morales, G. Orjeda, C. Clepet, A. Monfort, B. Sturbois, P.
Puigdomènech, M. Pitrat, M. Caboche, C. Dogimont, J. Garcia-
Mas, M.A. Aranda, and A. Bendahmane. 2006. An eIF4E allele
confers resistance to an uncapped and non-polyadenylated RNA
virus in melon. The Plant Journal 48: 452–462.
Nieto, C., F. Piron, M. Dalmais, C. Marco, E. Moriones, M.L. Gomez-
Guillamon, V. Truniger, P. Gomez, J. Garcia-Mas, M. Aranda, and
A. Bendahmane. 2007. EcoTILLING for the identification of allelic
variants of melon eIF4E, a factor that controls virus susceptibility.
BMC Plant Biology 7: 34.
Nowara, D., A. Gay, C. Lacomme, J. Shaw, C. Ridout, D. Douchkov, G.
Hensel, J. Kumlehn, and P. Schweizer. 2010. HIGS: host-induced
gene silencing in the obligate biotrophic fungal pathogen Blumeria
graminis. Plant Cell 22: 3130–3141.
NPC. 2014. National Potato Council. 2014 Potato Statistical Yearbook.
OECD. 1997. Organization for economic co-operation and development.
Consensus document on the biology of Solanum tuberosum subsp.
tuberosum (potato).
Office of Environmental Health Hazard Assessment. 2015. Acrylamide
Wor k plan .
Office of Science and Technology Policy. 1986. Coordinated framework
for regulation of biotechnology. Office of Science and Technology
Policy 51 FR 23302.
Paal, J., H. Henselewski, J. Muth, K. Meksem, C.M. Menendez, F.
Salamini, A. Ballvora, and C. Gebhardt. 2004. Molecular cloning
of the potato Gro1-4gene conferring resistance to pathotype Ro1 of
the root cyst nematode Globodera rostochiensis, based on a candi-
date gene approach. The Plant Journal 38: 285–297.
Pandey, P., M. Senthil-Kumar, and K. Mysore. 2015. Advances in plant
gene silencing methods. In Plant gene silencing, ed. K.S. Mysore
and M. Senthil-Kumar, 3–23. New York: Springer.
Panwar, V., B. McCallum, and G. Bakkeren. 2013. Host-induced gene
silencing of wheat leaf rust fungus Puccinia triticina pathogenicity
Am. J. Potato Res.

genes mediated by the Barley stripe mosaic virus. Plant Molecular
Biology 81: 595–608.
Papp, I., L. Mur, A. Dalmadi, S. Dulai, and C. Koncz. 2004. A mutation
in the cap binding protein 20 gene confers drought tolerance to
Arabidopsis. Plant Molecular Biology 55: 679–686.
Patterson, P. 2013. Cost and returns estimate: Eastern Idaho russet bur-
bank potatoes. EBB4-Po6-13. Moscow: University of Idaho.
Pel, M.A., S.J. Foster, T.-H. Park, H. Rietman, G. van Arkel, J.D.G.
Jones, H.J. Van Eck, E. Jacobsen, R.G.F. Visser, and E.A.G. Van
der Vossen. 2009. Mapping and cloning of late blight resistance
genes from Solanum venturii using an interspecific candidate gene
approach. Molecular Plant-Microbe Interactions 22: 601–615.
Perlak, F.J., T.B. Stone, Y.M. Muskopf, L.J. Petersen, G.B. Parker, S.A.
McPherson, J. Wyman, S. Love, G. Reed, D. Biever, et al. 1993.
Genetically improved potatoes: protection from damage by
Colorado potato beetles. Plant Molecular Biology 22: 313–321.
Petersson, E.V., U. Arif, V. Schulzova, V. Krtkova, J. Hajslova, J. Meijer,
H.C. Andersson, L. Jonsson, and F. Sitbon. 2013. Glycoalkaloid and
calystegine levels in table potato cultivars subjected to wounding,
light, and heat treatments. Journal of Agricultural and Food
Chemistry 61: 5893–5902.
Phillips, P., and D. Corkindale. 2002. Marketing GM foods: the way
forward. AgBioforum 5: 113–121.
Phipps, R., and J. Park. 2002. Environmental benefits of genetically mod-
ified crops: global and European perspectives on their ability to
reduce pesticide use. Journal of Animal and Feed Sciences 11: 1–18.
Pieczynski, M., W. Marczewski, J. Hennig, J. Dolata, D. Bielewicz, P.
Piontek, A. Wyrzykowska, D. Krusiewicz, D. Strzelczyk-Zyta, D.
Konopka-Postupolska, M. Krzeslowska, A. Jarmolowski, and Z.
Szweykowska-Kulinska. 2013. Down-regulation of CBP80 gene
expression as a strategy to engineer a drought-tolerant potato.
Plant Biotechnology Journal 11: 459–469.
Piron, F., M. Nicolai, S. Minoia, E. Piednoir, A. Moretti, A. Salgues, D.
Zamir, C. Caranta, and A. Bendahmane. 2010. An induced mutation
in tomato eIF4E leadstoimmunitytotwopotyviruses.PLoS ONE 5:
e11313.
Pliego, C., D. Nowara, G. Bonciani, D.M. Gheorghe, R. Xu, P. Surana, E.
Whigham, D. Nettleton, A.J. Bogdanove, R.P. Wise, P. Schweizer,
L.V. Bindschedler, and P.D. Spanu. 2013. Host-induced gene silenc-
ing in barley powdery mildew reveals a class of ribonuclease-like
effectors. Molecular Plant-Microbe Interactions 26: 633–642.
Puchta, H., and F. Fauser. 2014. Synthetic nucleases for genome engi-
neering in plants: prospects for a bright future. Plant Journal 78:
727–741.
Puchta, H., B. Dujon, and B. Hohn. 1996. Two different but related
mechanisms are used in plants for the repair of genomic double-
strand breaks by homologous recombination. Proceedings of the
National Academy of Sciences of the United States of America 93:
5055–5060.
Rigano, M.M., G. De Guzman, A.M. Walmsley, L. Frusciante, and A.
Barone. 2013. Production of pharmaceutical proteins in solanaceae
food crops. International Journal of Molecular Sciences 14: 2753–
2773.
Ron, M., and A. Avni. 2004. The receptor for the fungal elicitor ethylene-
inducing xylanase is a member of a resistance-like gene family in
tomato. The Plant Cell 16: 1604–1615.
Rousu, M., W. Huffman, J. Shogren, and A. Tegene. 2003. Are United
States consumers tolerant of genetically modified foods? Review of
Agricultural Economics 26: 19–31.
Ruffel, S., M.-H. Dussault, A. Palloix, B. Moury, A. Bendahmane, C.
Robaglia, and C. Caranta. 2002. A natural recessive resistance gene
against potato virus Y in pepper corresponds to the eukaryotic initi-
ation factor 4E (eIF4E). The Plant Journal 32: 1067–1075.
Ruffel, S., J.L. Gallois, M.L. Lesage, and C. Caranta. 2005. The recessive
potyvirus resistance gene pot-1is the tomato orthologue of the
pepper pvr2-eIF4E gene. Molecular Genetics and Genomics 274:
346–353.
Ruiz-Ferrer, V., and O. Voinnet. 2009. Roles of plant small RNAs in biotic
stress responses. Annual Review of Plant Biology 60: 485–510.
Scurrah, M., C. Celis-Gamboa, S. Chumbiauca, A. Salas, and R.F. Visser.
2008. Hybridization between wild and cultivated potato species in
the Peruvian Andes and biosafety implications for deployment of
GM potatoes. Euphytica 164: 881–892.
Shukla, V.K., Y. Doyon, J.C. Miller, R.C. DeKelver, E.A. Moehle, S.E.
Worden, J.C. Mitchell, N.L. Arnold, S. Gopalan, X. Meng, V.M.
Choi, J.M. Rock, Y.Y. Wu, G.E. Katibah, G. Zhifang, D.
McCaskill, M.A. Simpson, B. Blakeslee, S.A. Greenwalt, H.J.
Butler,S.J.Hinkley,L.Zhang,E.J.Rebar,P.D.Gregory,andF.D.
Urnov. 2009. Precise genome modification in the crop species Zea
mays using zinc-finger nucleases. Nature 459: 437–441.
Simon, W. 2003. The agricultural advantages and consumer acceptance
or otherwise of genetically modified crops with particular emphasis
on potatoes. Nuffield Reports: Biotechnology Reports. Nuffield
Farming Scholarships Trust 28.
Simplot. 2013. Petition for determinationof nonregulated status for innate
potatoes with low acrylamide potential and reduced black spot
bruise: events E12 and E24 (Russet Burbank); F10 and F37
(Ranger Russet); J3, J55, and J78 (Atlantic); G11(G); H37 and
H50 (H). J.R. Simplot Company.
Sindhu, A.S., T.R. Maier, M.G. Mitchum, R.S. Hussey, E.L. Davis, and
T.J. Baum. 2009. Effective and specific in planta RNAi in cyst
nematodes: expression interference of four parasitism genes reduces
parasitic success. Journal of Experimental Botany 60: 315–324.
Smith, D.B., J.G. Roddick, and J.L. Jones. 1996. Potato glycoalkaloids:
some unanswered questions. Trends in Food Science & Technology
7: 126–131.
Song, J., J.M. Bradeen, S.K. Naess, J.A. Raasch, S.M. Wielgus, G.T.
Haberlach, J. Liu, H. Kuang, S. Austin-Phillips, C.R. Buell, J.P.
Helgeson, and J. Jiang. 2003. Gene RB cloned from Solanum
bulbocastanum confers broad spectrum resistance to potato late
blight. Proceedings of the National Academy of Sciences of the
United States of America 100: 9128–9133.
Sparks, W., and L. Summers. 1974. Potato weight losses, quality chang-
es, and cost relationships during storage. AES Bulletin 535.
Moscow: University of Idaho.
Stein, N., D. Perovic, J. Kumlehn, B. Pellio, S. Stracke, S. Streng, F.
Ordon, and A. Graner. 2005. The eukaryotic translation initiation
factor 4E confers multiallelic recessive Bymovirus resistance in
Hordeum vulgare (L.). The Plant Journal 42: 912–922.
Stevens, L.H., and E. Davelaar. 1997. Biochemical potential of potato
tubers to synthesize blackspot pigments in relation to their actual
blackspot susceptibility. Journal of Agricultural and Food
Chemistry 45: 4221–4226.
Tinoco, M.L., B.B. Dias, R.C. Dall'Astta, J.A. Pamphile, and F.J. Aragao.
2010. In vivo trans-specific gene silencing in fungal cells by in
planta expression of a double-stranded RNA. BMC Biology 8: 27.
Toevs, E., J. Guenthner, A. Johnson, C. McIntosh, and M. Thornton.
2011a. Identity preservation systems for genetically modified pota-
toes. AmericanJournalofPotatoResearch88: 303–308.
Toevs, E., J. Guenthner, A. Johnson, C. McIntosh, and M. Thornton.
2011b. An industry perspective of all-native and transgenic potatoes.
AgBioforum 14: 14–19.
Tomilov, A.A., N.B. Tomilova, T. Wroblewski, R. Michelmore, and J.I.
Yoder. 2008. Trans-specific gene silencing between host and para-
sitic plants. Plant Journal 56: 389–397.
Townsend, J.A., D.A. Wright, R.J. Winfrey, F. Fu, M.L. Maeder, J.K.
Joung, and D.F. Voytas. 2009. High-frequency modification of plant
genes using engineered zinc-finger nucleases. Nature 459: 442–445.
Tynan, J., M. Williams, and A. Conner. 1990. Low frequency of pollen
dispersal from a field trial of transgenic potatoes. Journal of
Genetics and Breeding 44: 303–306.
Am. J. Potato Res.

USDA Nutrient Data Laboratory. 2015. National nutrient database for
standard reference release 27. http://ndb.nal.usda.gov. Accessed 15
May 2015.
USDA-APHIS. 2015. Petitions for determination of nonregulated
status. http://www.aphis.usda.gov/biotechnology/petitions_table_
pending.shtml. Accessed 31 August 2015.
van der Vossen, E., A. Sikkema, B. Hekkert, J. Gros, P. Stevens, M.
Muskens, D. Wouters, A. Pereira, W. Stiekema, and S. Allefs. 2003.
An ancient Rgene from the wild potato species Solanum
bulbocastanum confers broad-spectrum resistance to Phytophthora
infestans in cultivated potato and tomato. Plant Journal 36: 867–882.
van der Vossen, E.A., J. Gros, A. Sikkema, M. Muskens, D. Wouters, P.
Wolters, A. Pereira, and S. Allefs. 2005. The Rpi-blb2 gene from
Solanum bulbocastanum is an Mi-1gene homolog conferring broad-
spectrum late blight resistance in potato. Plant Journal 44: 208–222.
Van Eck, J., B. Conlin, D.F. Garvin, H. Mason, D.A. Navarre, and C.R.
Brown. 2007. Enhancing beta-carotene content in potato by RNAi-
mediated silencing of the beta-carotene hydroxylase gene. American
Journal of Potato Research 84: 331–342.
VanWechel, T., C. Wachenheim, E. Schuck, and D. Lambert. 2003.
Consumer valuation of genetically modified foods and the effect of
information bias. Agribusiness and Applied Economics Report No.
513. North Dakota State University.
Vega-Arreguin, J.C., A. Jalloh, J.I. Bos, and P. Moffett. 2014.
Recognition of an Avr3 a homologue plays a major role in mediating
nonhost resistance to Phytophthora capsici in Nicotiana species.
Molecular Plant-Microbe Interactions 27: 770–780.
Visser, R.G., I. Somhorst, G.J. Kuipers, N.J. Ruys, W.J. Feenstra, and E.
Jacobsen. 1991. Inhibition of the expression of the gene for granule-
bound starch synthase in potato by antisense constructs. Molecular
and General Genetics 225: 289–296.
Vleeshouwers, V.G., H. Rietman, P. Krenek, N. Champouret, C. Young,
S.K. Oh, M. Wang, K. Bouwmeester, B. Vosman, R.G. Visser, E.
Jacobsen, F. Govers, S. Kamoun, and E.A. Van der Vossen. 2008.
Effector genomics accelerates discovery and functional profiling of
potato disease resistance and Phytophthora infestans avirulence
genes. PLoS ONE 3: e2875.
Vossen, J., S. Dezhsetan, D. Esselink, M. Arens, M. Sanz, W. Verweij, E.
Verzaux, and C. van der Linden. 2013. Novel applications of motif-
directed profiling to identify disease resistance genes in plants. Plant
Methods 9: 37.
Waltz, E. 2012. Tiptoeing around transgenics. Nature Biotechnology
30: 215–217.
Weisz, R., J. Kaminski, and Z. Smilowitz. 1994. Water deficit effects on
potato leaf growth and transpiration: utilizing fraction extractable
soil water for comparison with other crops. American Potato
Journal 71: 829–840.
West, G., C. Gendron, B. Larue, and R. Lambert. 2002. Consumers’
valuation of functional properties of foods: results from a Canada-
wide survey. Canadian Journal of Agricultural Economics 50: 541–
588.
Wright, D.A., J.A. Townsend, R.J. Winfrey Jr., P.A. Irwin, J. Rajagopal,
P.M. Lonosky, B.D. Hall, M.D. Jondle, and D.F. Voytas. 2005.
High-frequency homologous recombination in plants mediated by
zinc-finger nucleases. Plant Journal 44: 693–705.
Xie, F., T.P. Frazier, and B. Zhang. 2011. Identification, characterization
and expression analysis of microRNAs and their targets in the potato
(Solanum tuberosum). Gene 473: 8–22.
Yadav, B.C., K. Veluthambi, and K. Subramaniam. 2006. Host-generated
double stranded RNA induces RNAi in plant-parasitic nematodes
and protects the host from infection. Molecular and Biochemical
Parasitology 148: 219–222.
Yang, W., X. Liu, J. Zhang, J. Feng, C. Li, and J. Chen. 2010. Prediction
and validation of conservative microRNAs of Solanum tuberosum
L. Molecular Biology Reports 37: 3081–3087.
Ye, J., R. Shakya, P. Shrestha, and C.M. Rommens. 2010. Tuber-specific
silencing of the acid invertase gene substantially lowers the
acrylamide-forming potential of potato. Journal of Agricultural
and Food Chemistry 58: 12162–12167.
Yin, C., J.E. Jurgenson, and S.H. Hulbert. 2011. Development of a host-
induced RNAi system in the wheat stripe rust fungus Puccinia
striiformis f. sp. tritici. Molecular Plant-Microbe Interactions 24:
554–561.
Yoshii, M., M. Nishikiori, K. Tomita, N. Yoshioka, R. Kozuka, S. Naito,
and M. Ishikawa. 2004. The Arabidopsis cucumovirus multiplica-
tion 1 and 2 loci encode translation initiation factors 4E and 4G.
Journal of Virology 78: 6102–6111.
Yuan, B.-Z., S. Nishiyama, and Y. Kang. 2003. Effects of different irri-
gation regimes on the growth and yield of drip-irrigated potato.
Agricultural Water Management 63: 153–167.
Zhang, B., X. Pan, Q. Wang, G.P. Cobb, and T.A. Anderson. 2006.
Computational identification of microRNAs and their targets.
Computational Biology and Chemistry 30: 395–407.
Zhang, W., Y. Luo, X. Gong, W. Zeng, and S. Li. 2009. Computational
identification of 48 potato microRNAs and their targets.
Computational Biology and Chemistry 33: 84–93.
Zhang, H., J.Guo, R.T. Voegele, J. Zhang, Y. Duan, H. Luo, and Z. Kang.
2012. Functional characterizationof calcineurin homologs PsCNA1/
PsCNB1 in Puccinia striiformis f. sp. tritici using a host-induced
RNAi system. PLoS ONE 7: e49262.
Zhang, R., D. Marshall, G.J. Bryan, and C. Hornyik. 2013. Identification
and characterization of miRNA transcriptome in potato by high-
throughput sequencing. PLoS ONE 8, e57233.
Zipfel, C. 2014. Plant pattern-recognition receptors. Trends in
Immunology 35: 345–351.
Am. J. Potato Res.