What does GM potatoes mean for future blight control?

If you asked consumers whether they would like to buy potatoes which hadn’t been sprayed eight to 10 times for potato blight, one would assume most would be in favour.

Of course, ask them if they wanted to eat genetically-modified spuds and the answer might be very different.

Commercially that’s what BASF will have to work hard to overcome in the next eight to 10 years – it is going to be that long before its blight-resistant GM potatoes are likely to be launched.

Proving the technical performance looks like it should be much more straightforward. Initial trials conducted in Sweden in the past two years, and in Germany and Holland last year, have shown a very high level of blight resistance, according to Andy Beadle, BASF project manager.

“In the trials I’ve seen we haven’t needed to spray the potatoes for blight after we’ve inoculated with the disease.”

Way ahead

That puts them way ahead of most commercial varieties for blight resistance. “We’ve been doing work with the breeders, who have a mechanism for scoring blight resistance when they are developing varieties, and most of our GM varieties have been scoring 8 or 9 for resistance.

“The breeders themselves have been very impressed. It looks like this could be a quantum leap forward.” Most commercial second early or maincrop varieties score 6 or below for blight resistance.

The genes BASF has been using to create the increased resistance to blight come from a wild potato relative, which probably developed its resistance because it co-evolved with the fungus in Mexico.

Scientists have known about the gene since the 1950s, but, according to BASF, it has proved impossible to cross it with cultivated potatoes. The only method to transfer the resistance has been through biotechnology.

Introducing the genes seems a bit of a scattergun affair. “When you insert the gene into the plant there are many events, ie it goes into the plant in many places,” Mr Beadle explains.

Positive effect 

The first two years of trials have been discovering which of these events have a positive effect. “We have a significant number of events we are pursuing – we started with over 500 – but expect to initially select just three to go forward with by 2008.”

The first generation product uses two genes from the wild relative to confer resistance. “The genes operate in completely different ways.”

The mechanism is a common plant defence reaction in nature. When the plant is infected with blight the gene causes the tissue around the infection to die off, stopping the spread of the disease.

But by having two different modes of action the firm believes it should help combat resistance development. “It means the beastie has to evolve to get round both resistance sources, and we have other resistance genes that we can use in future products to complement and enhance resistance.”

The next set of trials will begin to assess the wider management implications of using the technology. At the moment BASF is, perhaps understandably, being cautious about suggesting it will stop the need for blight sprays. “Our hypothesis is it will dramatically reduce blight sprays, but to get the most out of the technology we need to use an integrated management strategy,” Mr Beadle says. “At a minimum the trait should significantly increase spray intervals.”

It could go further – the evidence to date suggests the genes can give season-long control without the need for follow-up sprays. But that needs to be tested in UK conditions, and over a number of years to investigate reliability and durability. And even if blight is effectively controlled there could still be a need to spray fungicides for other diseases because the genes are specific for blight.

The planned field trials in Cambridgeshire and Derbyshire are only the start of a development programme to select the final variety, BASF says. “From that point eight to 10 years are needed before it can be introduced into the market.”

That might be just as well – the PR campaign for public support no doubt starts now.

*For industry reaction to the announcement of the trials go-ahead see News. More details can be found at www.defra.gov.uk/environment/gm/regulation/consents/index.htm

  • Two trials approved by DEFRA
  • Located in Cambridgeshire and Derbyshire
  • Test blight resistance in UK conditions
  • Two genes confer resistance
  • Found in wild potato relative


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