Genetically Engineered (GE) Papaya – Unknown Fruit
Greenpeace Briefing Updated June 2005
Summary
Genetic engineering is a crude and old fashioned technology. The mechanism by which
genetically engineered (GE) papaya is resistant to Papaya Ringspot virus (PRSV) is not
known. The environmental risks of GE papaya are difficult to define because of the lack of
scientific understanding about ecological interactions and possibility of unexpected effects.
Possible environmental effects include the creation of new strains of viruses with unknown
consequences. GE papaya cannot be controlled. There is widespread contamination of
papaya, including organic papaya in Hawaii, the only place where GE papaya is grown
commercially. There has already been contamination from an experimental field trial in
Thailand, where an extensive operation is underway to contain the contamination.
Commercial growing in Thailand would lead to widespread contamination, such as that now
present in Hawaii, which is likely to result in loss of export markets. Advances are being
made to produce a non-GE papaya that is resistant to PRSV using a different approach, that
of marker assisted selection. GE papaya poses unpredictable and unexpected risks with
unknown consequences to the environment. The precautionary principle should be employed
and there should be no releases of GE papaya to the environment. Resources should be
redirected developing the alternatives to GE papaya.
Introduction
The Papaya Ringspot virus (PRSV) affects papaya plantations in Hawaii, Florida, South America,
Africa, Australia and SE Asia. Papaya has been genetically engineered (GE) to be resistant to the
PRSV. GE papaya has been grown in Hawaii in recent years and now it is suggested that Thailand
could grow GE papaya. But, GE is a crude and imprecise technology, subject to unexpected and
unpredictable effects. In addition, the GE papaya for Thailand has been developed in the laboratory
completely separately from the Hawaiian GE papaya, so any assurances on the safety of the GE
papaya in Hawaii do not apply to the Thai GE papaya.
This briefing examines the environmental risks of GE papaya in Thailand. It is based on a scientific
report1 written by the Institute for Applied Ecology, Germany, commissioned by Greenpeace. The
human health risks of GE papaya are described in a separate briefing2
Genetically Engineered Papaya – crude science
GE is a crude and old fashioned technology. Artificial genetic constructs are inserted randomly and
often forcibly into an organism. GE relies on a theory developed in the 1950s and assumes that
each gene has only one function. However, today it is known that genes are much more complex
than this3. Gene expression is controlled by complex regulatory networks in a manner that is far
from being fully understood. GE can never produce an organism that is acceptable to be released
into the environment and food chain because it cannot incorporate the complex regulatory networks
now known to exist in organisms such as plants.
No one knows how GE papaya is resistant to PRSV.
The GE papaya contains a gene from the PRSV but the exact mechanism of how GE papaya is
resistant to PRSV isn’t known. The theory of how it works has changed as more becomes known
about how DNA and viruses function4.
Gene gun
The GE papaya may work because of the crude methods of GE. The GE engineering technique
used for papaya is biolistics or particle bombardment. This technique often unintentionally
produces multiple copies of the inserted gene and additional, partial fragments of the gene. It has
been suggested that the resistance of GE papaya to the virus is due, in part, to these unintended
additional copies and fragments5.
GE papaya will not be resistant to all strains of PRSV
Hawaii is geographically isolated and so there are only a limited number of types of PRSV. Even
so, Hawaiian growers of the most widely grown GE PRSV resistant papaya (Rainbow) are
concerned that imports may bring additional types of PRSV into Hawaii that the GE papaya may
not be resistant to6. The situation in Thailand is very different from Hawaii: it is not so
geographically isolated and there are many different types of PRSV in SE Asia, both within
Thailand (for example, Kon Kaen, Chaing Mai and Ratchaburi strains) and neighbouring countries.
Any GE PRSV resistant papaya will only be resistant to one, or possibly a few, types of the virus.
Therefore, GE papaya will not provide any long-term resistance to PRSV because there are so many
strains in the region.
Environmental risks of GE papaya
The environmental risks of GE papaya cannot be predicted with any certainty. It is unknown how
this GE papaya will impact ecosystem or how it will interact with the many other organisms present
in the environment. There are almost no studies examining the interaction of GE papaya with other
organisms, or indeed other viruses. There are no other GE crops resistant to viruses grown
commercially in the world apart from GE papaya in the geographically isolated islands of Hawaii.
Therefore, any risk assessment is guess work, as it is not even known how many and what kind of
environmental interactions (e.g. with other organisms) exist and need to be assessed. However,
risks include the possibility of the creation of new strains of viruses and irreversible spread of the
gene through the papaya population.
Creation of new virus strains
The interaction of GE papaya with other viruses that also infect the plant can produce new strains of
viruses. A virus infecting a GE papaya plant could be altered in a number of different ways.
1) the range of organisms that the virus can infect could change, e.g. a virus could start
infecting other types of plants which is did not previously;
2) the way the virus is carried could change, e.g. a virus not previously passed on by insects
could become carried by insects;
3) the strength (or virulence) of the virus could be altered
4) or recombination could produce a new virus.
The consequences of any of these happening are completely unknown.
Papaya Ring Spot Virus
How likely is the creation of new virus strains from GE papaya?
It isn’t known how likely interactions that may create new strains of viruses are. The research
simply has not been done – how new strains of viruses evolve isn’t well understood. However,
recent research with mosaic viruses has shown that recombination of viruses is much more common
than previously thought7. The possibility of creations of new virus strains could not be evaluated
during field trails, as it is the type of event whose frequency is relatively low, but would only need
to happen once to create a new strain.
The geographical isolation of Hawaii means that the GE papaya grown there isn’t exposed to so
many viruses. In areas such as South-East Asia there are a great many types of virus of the same
family (potyviruses), unlike Hawaii and indeed, a great variety of PRSV types, e.g. Chiang Mai
isolate. There are also many viruses that infect papaya plants at the same time as PRSV, again a
different situation to Hawaii. Therefore, there is a greater chance of interaction between GE papaya
and other viruses in areas such as South East Asia.
There are two other factors, related to the genetic engineering itself that increase the chance for
interaction between the GE papaya and incoming viruses. The genetic insert in GE papaya is
always “on”, i.e. it does not switch off and on and is therefore producing protein all the time in
every cell of the plant. Therefore, any virus infecting the plant will automatically be exposed to
protein, increasing the risk of interaction between the incoming virus and the GE papaya. In natural
conditions, two different viruses do not affect the same cell at the same time but this effectively
could happen with the GE papaya.
Hence, there are important differences between a virus infecting GE papaya and natural co-infection
of viruses. These differences may be important in producing new strains of viruses, but knowledge
of viruses and their evolution is so limited, that predictions simply cannot be made.
Contamination of non-GE papaya is happening
Recently, there have been cases of GE contamination from both Hawaii (where GE papaya is
commercially grown) and Thailand (where the contamination originated from a field trial.
Contamination in Hawaii
The extent to which GE contamination of non-GE papaya by cross-pollination is a problem in
Hawaii is illustrated by the widespread contamination and extra-ordinary efforts that growers of non
GE papaya growers have to take to ensure their papaya is non GE.
Testing of seed samples from Hawaii by an independent GE testing company has shown that
approximately 50 % of samples thought to be non-GE, mostly organic, papaya were contaminated
by GE papaya8. Thus, there is widespread contamination of GE papaya in Hawaii.
Concern over loss of markets, e.g. to Japan and the EU where GE papaya is not authorized for sale
has led to the Hawaii Department of Agriculture (HDOA) setting up a complex and rigorous
programme of identity preservation of non GE papaya9.
To get an HDOA certificate of being GE free, “every tree in the proposed field must be initially
tested for the transgenic reporter gene (1,3-β-glucoronidase) that is linked to the virus resistance
gene, and found negative; the trees (nontransgenic) must be separated by at least a 15-foot papayafree buffer zone; and new fields that are to be certified must be planted with papaya seeds that have
been produced in approved non-GMO fields. Tests for detecting transgenic papaya trees in the
fields are monitored by HDOA and conducted by the applicant who must submit detailed records to
HDOA. Before final approval of a field, HDOA will randomly test one fruit from 1% of papaya
trees in the field. If approved by HDOA, fruit from these fields can be harvested. Additionally, the
applicant must submit the detailed protocols that the applicant will follow to minimize the chance of
contamination of non-GMO papaya by GMO papaya. This includes a protocol by the applicant on
the random testing of papaya before they are packed for shipment.”10
Despite all these precautions, in 2004 GE papaya from Hawaii was found in the EU, discovered by
the German authorities11. The German authorities are now testing Hawaiian imports of papaya to
check they are not contaminated with GE papaya12.
Contamination in Thailand
In 2004, Greenpeace revealed13 contamination of papaya from GE PRSV resistant papaya grown
from an experimental field trial at a government research station in Khon Kaen. Since then, the
Thai government has ordered the destruction of the field trial at the research station in Khon Kaen
and started to control and destroy GE papaya in farmers’ fields. This contamination can only have
arisen from GE papaya being grown experimentally at the research station, because GE papaya is
not grown commercially in Thailand14. Exports of papaya to Europe have been hit because of fears
that contamination could have spread.
Testing of GE papaya in Thailand is problematic. There is no validated test because only those GE
crops that are commercialized can be tested. Therefore, only certain elements of the GE papaya
(the CMV35S promoter and NOS “stop”, which are common to most GE crops) can be detected by
independent GE testing companies15. This is hampering independent efforts to determine the source
and extent of the contamination.
Consequences of contamination
The consequences of GE contamination are not predictable because GE is such a crude technology.
There have been several examples of unexpected effects of commercial GE plants; some of these
only became obvious when the GE plant was under stress, such as drought or high temperatures.
For example, Monsanto’s Roundup Ready soya gave rise to unexpected crop losses in hot, dry
weather due to stem splitting caused, most probably, by increased lignin16. It has been reported that
the GE papaya grown on Hawaii is unexpectedly susceptible to black spot fungus and requires
additional spaying of fungicides17. Therefore, the spreading of a gene through the population of
papayas could have unintended consequences.
GE contamination of papaya plants could increase the likelihood of virus recombination, because of
the greater abundance of GE papaya plants. Importantly, GE contamination would restrict seed
production for non-GE papaya and could impact the export market for Thai papaya.
The escape of GE papaya from a experimental field trial is particularly worrying because no human
food safety, nor environmental studies have been completed. It is completely unknown whether it is
safe to eat.
These contamination cases show that GE papaya cannot be controlled. There
cannot be coexistence of GE and non-GE papaya.
Are there alternatives?
Non GE-papayas that are resistant to PRSV are being developed, e.g. by crosses with other types of
papaya18. Indeed, the search for papayas resistant to PRSV is a principal reason cited for
conservation of papayas in Southern Ecuador (a centre of diversity for papayas)19. Such crosses
have previously resulted in low pollen fertility, but efforts are currently underway to improve pollen
fertility20. These research efforts use marker assisted selection, a modern biotechnological approach
that does not result in a GE crop being released to the environment.
Conclusion
It is evident that GE papaya cannot be controlled. Commercial growing in Thailand would lead to
widespread contamination, such as that now present in Hawaii. There has already been
contamination from an experimental field trial in Thailand that is requiring an extensive operation
to prevent further damage.
GE papaya poses unpredictable and unexpected risks with unknown consequences to the
environment. The precautionary principle should be employed and there should be no releases of
GE papaya to the environment. Resources should be redirected developing the alternatives to GE
papaya.
1
Moch, K. & Tappeser, B. (2003) Ecological risks of virus resistant transgenic plants: a case study of virus resistant
transgenic papaya. Institute for Applied Ecology, Germany.
2
Hansen, M (2005) Problems with GM papaya Potential Human Health Effects of Genetically Engineered/Genetically
Modified (GE/GM) papaya. http://www.greenpeacesoutheastasia.org
3
Greenpeace (2003) 50 years since the double helix: genetic engineering is crude and old-fashioned (and references
therein). http://www.greenpeace.org
4
Bau, H.-J., Cheng, Y.-H., Yu, T.-A., Yang, J.-S. & Yeh, S.-D. (2003) Broad-spectrum resistance to different
geographic strains of Papaya ringspot virus in coat protein gene transgenic papaya. Phytopathology, 93, 112-120.
5
Lines, R.E., Persley, D., Dale, J.L., Drew, R. & Bateson, M.F. (2002) Genetically engineered immunity to Papaya
ringspot virus in Australia papaya cultivars. Molecular Breeding, 10, 119-129.
6
Tennant, P. F., Gonsalves, C., Ling, K-S., Fitch, M., Manshardt, R., Slightom, L. J, and Gonsalves, D. (1994)
Differential protection against papaya ringspot virus isolates in coat protein gene transgenic papaya and classically
cross-protected papaya. Phytopathology 84, 1359-1366.
Gonsalves, D., Gonsalves, C., Ferreira, S., Pitz, K., Fitch, M., Manshardt, R. & Slightom, J. (2004) Transgenic virus
resistant papaya: from hope to reality for controlling papaya ring spot virus in Hawaii. Online APSnet feature,
American Phytopathology Society. July-August http://www.apsnet.org/online/feature/ringspot/
7
Froissart, R., Roze, D., Uzest, M., Galibert, L., Blanc, S. & Michalakis, Y. (2005) Recombination every day: abundant
recombination in a virus during a single multi-cellular host infection. PLoS Biology, 3, e89.
Bonnet, J., Fraile, A., Sacristán, S., Malpicab, J.M., García-Arenala, F. (2005) Role of recombination in the evolution of
natural populations of Cucumber mosaic virus, a tripartite RNA plant virus. Virology, 332, 359-368.
8
GMO-free Hawaii. New research reveals widespread GMO contamination and threats to local agriculture from the
University of Hawaii’s GMO papaya http://www.higean.org/news.htm#papaya
9
Gonsalves, D., Gonsalves, C., Ferreira, S., Pitz, K., Fitch, M., Manshardt, R. & Slightom, J. (2004) Transgenic virus
resistant papaya: from hope to reality for controlling papaya ring spot virus in Hawaii. Online APSnet feature,
American Phytopathology Society. July-August http://www.apsnet.org/online/feature/ringspot/
10
Gonsalves et al. (2004) op. cit.
11
Busch, U., Pecoraro, S., Posthoff, K. & Estendorfer-Rinner, S. (2004) First time detection of a genetically modified
papaya in Europe - Official complaint of a non authorized genetically modified organism within the EU. Deutsche
Lebensmittel-Rundschau, 100, 377-380.
12
EC Standing Committee on the Food Chain and Animal Health. Section on Genetically Modified Food and Feed and
Environmental Risk. Summary record of the 4th meeting – 25 January 2005
http://europa.eu.int/comm/food/committees/regulatory/scfcah/modif_genet/summary04_en.pdf
13
http://www.greenpeace.org/international/news/ge-papaya-scandal-in-thailand
14
The Nation (Thailand) 1,000 GM papaya trees felled.
http://www.nationmultimedia.com/page.news.php3?clid=3&id=120934& usrsess=1
15
Letter to Greenpeace from Genescan, an independent GE testing company. 8th October 2005
16
Coghlan A (1999) Splitting headache. Monsanto’s modified soya beans are cracking up in the heat.New Scientist,
20th November, p. 25.
17
Hawaiian Island Journal. (2003) Plenty papaya problems. 16th April.
http://www.hawaiiislandjournal.com/stories/4a03a.html
18
Magdalita, P.M., Drew, R.A., Godwin, I.D. & Adkins, S.W. (1998) An efficient interspecific hybridisation protocol
for Carica papaya L. X C. cauliflora Jacq. Australian Journal of Experimental Agriculture, 38, 523-530.
19
Scheldeman, X. & Van Damme, P.V. (2002) Highland papayas in Southern Ecuador: need for conservation actions.
ISHS Acta Horticulturae 575: International Symposium on Tropical and Subtropical Fruits, 199-205.
20
Magdalita, P.M., Godwin, I.D. & Drew, R.A. (2002) Randomly amplified polymorphic DNA markers for a Carica
interspecific hybrid. . ISHS Acta Horticulturae 575: International Symposium on Tropical and Subtropical Fruits,
133-139.