ISIS Report 12/07/10
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While researchers are wasting taxpayers’ money to create hazardous GM blight-
resistant potatoes, non-GM highly blight-resistant varieties are already on the
market, with low carbon impact and all-round appeal to consumers Dr Eva Novotny
A new trial of genetically modified (GM) crops has begun in England [1]. The
Sainsbury Laboratory at the John Innes Centre in Norfolk is testing a GM version
of the popular Desiree potato to determine whether, as in the laboratory, the
field-grown GM potato will remain resistant to late-blight disease. The
challenge to develop such potatoes had already been taken up in 2007 by the
German chemical giant BASF, in its Plant Science GmbH division; but their trials
ended prematurely without a marketable result. In fact, all such efforts are
unnecessary, as blight-resistant non-GM potatoes already exist that are also
outstanding in other respects, and further such varieties are in the pipeline.
Late blight is a serious disease of potatoes
Late blight is “ the most devastating disease of potatoes and one of the most
devastating plant diseases of any crop [2, 3].” In the UK, farmers typically
spray potato crops with fungicide 10-15 times a year [4]. Much effort,
therefore, has been put into means of controlling the disease. As part of good
farming practice, it is clearly advantageous to plant blight resistant
varieties.
The disease can kill all the leaves of a plant within 10 days. It was the cause
of the great Potato Famine in Ireland and western Scotland in the 1840s and
1850s. The pathogen responsible is Phytophthera infestans, notionally a fungus
but actually more closely related to brown seaweeds. Warm, humid weather
favours the disease. Leaves and stems can be infected, as can the tubers when
spores are washed into the soil by heavy rain. The disease can be carried from
year to year by tubers that were infected in the previous season. Although soil
is not usually a source of the blight, it is possible for the disease to be
transmitted when both mating types of the blight pathogen (see [5] GM Potatoes
not Proven Safe for Release, SiS 47) are present in the soil. In gardens, it is
possible for the disease to be carried over on infected foliage in an
insufficiently hot compost heap.
Unfortunately, the pathogen is evolving. Until 1976, there was only the single
mating type A1, which had various strains, all reproducing asexually. Then
mating type A2 appeared in Europe, brought from Mexico (the probable origin of
the blight pathogens) on imported potatoes. The two types were able to mate and
produced new strains by sexual reproduction. Since 2005, a highly aggressive
strain A2-Blue13 has developed; causing blight in some potato varieties that
were previously resistant, and it has become the dominant strain in the UK.
There is always the danger that the pathogen will evolve into a new strain that
can overcome the resistance of potato varieties now free of the disease, and
development of new varieties needs to take place on a continuing basis.
New trial by the Sainsbury Laboratory
The Sainsbury Laboratory at the John Innes Centre in Norfolk, England has
received approval for field trials of GM blight-resistant potatoes, beginning in
2010. The Laboratory claims that existing non-GM blight-resistant potatoes
suffer from “other deficiencies”, but this claim cannot justly be applied to
Sárpo potatoes, described later.
Natural resistance to blight occurs in some wild, inedible potato species in
South America. Two genes isolated from these have been transferred to a potato
variety popular in Britain, Desiree [4, 5], and will undergo field trials for
three years.
Justifying the use of genetic engineering to produce the new potatoes, the
Laboratory claims that [4]: “Potato breeding is extremely slow and inefficient.
… Breeding is not an exact science and changes many genes that affect important
agronomic traits such as yield, quality and maturity time. By using GM we can
be sure that only the desired resistance gene is introduced into the resulting
variety, without changing other characteristics.” This disingenuous statement is
actually false: it is well known that the random insertion process of genetic
engineering leads to disruption and rearrangement in the host’s own genome,
causing ‘insertion mutagenesis’ in many genes with totally unpredictable effects
(see review in [6] The Case for A GM-Free Sustainable World, Independent Science
Panel, ISIS publication).
The GM potato also has an antibiotic resistance marker gene nptII that confers
resistance to kanamycin and neomycin [7]. The Laboratory claims erroneously
that the antibiotic is not used for medical treatment of either humans or
animals. The Advisory Committee on Releases to the Environment (ACRE) gave an
approving opinion for the trials, on grounds that [7]: “(a) the likelihood of
transfer of a functional gene from plant material tobacteria is extremely low;
(b) bacteria with resistance to these antibiotics arewidespread in the
environment; and (c) the acquisition of an intact gene isonly one of the
possible mechanisms by which bacteria may developresistance.” This is
essentially the same opinion delivered by the pro-GM European Food Safety
Authority (EFSA) when it examined the use of antibiotic resistance genes in food
crops. On that occasion, however, two senior scientists on the panel disagreed
and issued a minority opinion in an annex to the statement, saying it was not
possible to assess any adverse effects and that the probability that the gene
could transfer from the GM plants to environmental bacteria was between
‘unlikely’ and ‘high’ (see [8] GM DNA Does Jump Species, SiS 47).
The Norfolk trials are funded entirely by UK taxpayers, through the
Biotechnology and Biological Sciences Research Council (BBSRC) [4]. This is
unfortunate and a waste of taxpayers’ money, as even a Monsanto representative
acknowledged that “ultimately [non-GM] biotech offers the greatest potential”
for developing crops with such complex traits [9].
Another questionable aspect of the trials, and indeed of the whole project, is
that the parent variety Desiree is already widely planted. Thus, a newly
invading disease affecting the GM potato may wipe out a major portion of the
UK’s potato harvest, both GM and non-GM.
In fact, GM potatoes for late-blight resistance had already been trialled and
abandoned by another corporation. German chemical company BASF had produced GM
blight-resistant potatoes. Field trials were started in 2007, originally
planned for the Irish Republic but moved to England after the Irish authorities
placed very high requirements on the conduct of the trials, especially the
requirement for safety testing by feeding the potatoes to animals prior to
commencement of trials.
Read the rest of this report at the ISIS website:
http://www.i-sis.org.uk/GM_Blight-resistant_Potatoes.php
Or read other reports about genetic engineering in agriculture
http://www.i-sis.org.uk/GE-agriculture.php
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