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An application has been made to test genetically-modified blight- resistant
potatoes in the UK. But is GM the only way forward? Teresa Rush reports,
BASF's announcement that is has applied to Defra to trial
genetically-modified blight resistant potatoes in the UK (see Arable Farming
September 4 issue) has inevitably re-focused attention on the question of
whether or not GM has a place in UK agriculture.
But, as next month's deadline for responses to the Government's GM co-
existence consultation approaches, opinion appears to be as divided as ever.
In a straw poll conducted by Arable Farming's weekly sister publication,
Farmers Guardian, responses to the question 'Should we grow GM potatoes in
the UK?' were split pretty much down the middle, with the 'no' respondents
including GM Freeze, the Soil Association and the Food Ethics Council and
the 'yes' respondents including growers and the biotechnology
industry-supported information initiative CropGen. However, not all of the
growers answering 'no' were organic producers.
In addition to the GM - yes or no question BASF?s application has also
brought into focus a number of issues relating to blight control in the UK:
Is it becoming more difficult and expensive? Is there blight resistance
available in conventionally-bred potato varieties? Are the BASF GM varieties
resistant to the A2 blight strain?
In a report prepared for the Pesticides Safety Directorate, published at the
beginning of this year, David Green of ADAS noted that data gathered for the
agrochemical industry showed a trend towards an increase in the numbers of
fungicides being applied to potato crops. The total value of blight
fungicides applied to crops in 2004 was estimated as ?19 million. The report
also highlighted an increasing trend towards starting spray programmes
earlier and maintaining intervals between applications cioser to routine
seven-day intervals. lronically it would seem that this trend is driven by
consumer demand for disease and blemish-free potatoes.
"There is ample anecdotal evidence that retailer quality demands are such
that growers will not take chances with late blight and the financial
penalties associated with tuber infection," the report concludes.
PSD's own pesticide usage data for 2004, the most recent available, shows
that ware potato crops received on average ten fungicides, accounting for
62% of the total pesticide-treated area of ware potatoes. The equivalent
figures for 2002 were nine fungicides and 61% and for 2000, eight fungicides
There is anecdotal evidence too, from growers and agronomists, that blight
control is requiring increased levels of fungicide inputs. TAG potato
specialist Denis Buckley believes that the evolution of the Phytophthora
infestans fungus is making the disease increasingly difficult to contain.
"Blight control is becoming increasingly difficult to achieve. Either the
market accepts newer, conventional varieties, we go down the GM route or we
use more fungicides," he says.
One of the key issues occupying the minds of blight control experts
currently is that of the spread of the A2 mating type of Phytophthora
infestans. First detected in the UK in 1981 it is believed by some
scientists to be more aggressive than the Al type, potentially requiring
more robust fungicide programmes to achieve control. Fungicides appear to
provide control of the A2 strains, although there is evidence of resistance
to the phenylamide metalaxyl.
In sampling last year A2 strains were detected at 38 out of 99 sample sites,
predominantly in the south west but also in Scotland and the eastern
counties. According to David Shaw of the Savari Research Trust, none of the
strains identified during 2005 were detected during sampling carried out
between 1995 and 1998, when most of the A2s were of a single strain.
lt's not yet clear whether BASF's GM potatoes are resistant to the A2 types.
GM project leader Andrew Beadle points out that one of the reasons that the
company is seeking to test its GM potatoes in the UK is to assess the
materials' resistance to the A2 blight strains. "Our assumption is that it
will be resistant. We are trying to produce a plant that has broad
resistance," he says.
BASF currently has "at least three" GM varieties in trials in Sweden,
Germany and Holland. When scored for blight resistance on the same scale as
conventional varieties the rating of the current GM material is
'significantly higher', says Mr Beadle.
According to plant pathologist Dr David Cooke of the Scottish Crop Research
Institute very few conventionally-bred varieties have full resistance to
blight but there is "pretty good" resistance already available in varieties
like the early maincrop Lady Balfour, bred by SCRI in 2001 and the Sarpo
varieties from Hungary.
While organic growers have taken up some of these varieties, most are not
widely grown commercially, he says. In some cases improved blight resistance
has come at the cost of other, less desirable, agronomic traits such as late
maturity, but there is also reluctance in the marketplace to adopt new
varieties - the UK potato acreage is dominated by fewer than 10 varieties.
Defra's Advisory Committee an Releases to the Environment (ACRE) will
consider BASF's application to trial GM potatoes in the UK at its meeting in
September. If approval is granted and the trials go ahead, they will be the
first GM field trials since the Farm Scale Evaluations in 2003.
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