This summer saw the start of new Irish trials investigating potatoes containing the blight-resistant gene (Rpi-vnt 1) from a wild South American relative.

The four-year European-funded project is part of a large EU-wide study involving 22 institutions across 15 countries assessing the impact of GM plants on agro-ecosystems. It is focusing on two crops: Bt maize and blight-resistant potatoes.

The team at Teagasc are investigating the effect the GM potato line might have, over a number of seasons, on soil microbes, earthworms and nematodes – the barometers of soil health. This is an area that hasn’t been looked at for many GM crops, explains senior research officer Ewen Mullins.

“We also want to see how blight is going to respond when it is exposed to these R-genes coming from the wild potato species, such as the rate of genetic change in the pathogen, Phytopthora infestans.”

There are other aspects of the project including integrated pest management, which is really important if the durability of the lines is to be prolonged in the future, explains Dr Mullins. Growers need to adopt a more targeted approach to what, when and how much to spray, assuming they are required.

Cisgenic technology

The potatoes used in the trial have been engineered using cisgenic technology through the DuRPH project at Wageningen University, which Dr Mullins believes is critical because it removes the ethical issue for many people.

Cisgenic is where a natural gene coding for a trait from the plant itself or from a closely related donor plant, such as the wild South American potato, is used rather than a gene from a non-related species.

“According to an EU report in 2010, in Ireland acceptance for GM was 36% and this nearly doubled to 61% for cisgenic modification. Dr Mullins believes that three years-worth of field studies is required before conclusions can be drawn.

In contrast to the environmental work being carried out in Ireland, researchers at the Sainsbury Laboratory in Norwich are nearing the end of a three-year field release study granted by DEFRA to look at confirming how the resistance genes work in the open field.

“Without exposing the gene to a true natural population you can’t say for certain whether there might be blight strains that overcome the gene,” says Simon Foster, laboratory manager at the Sainsbury Laboratory.

Trial results have shown that the Rpi-vnt 1 gene works very well in the field and is effective against all the UK strains tested, including the A1-pink 6 and A2-blue 13 strains and Green-33, the strain in the Netherlands that shows reduced sensitivity to fluazinam.

Work will continue with the Rpi-vnt 1 gene with the ultimate aim of combining multiple resistance genes within a single cultivar to improve the spectrum of resistance, as well as make the resistance more durable, explains Dr Foster. Although Desiree is currently being trialed, other cultivars, such as Maris Piper, may be included.

“We know more about how the R-genes actually work, so we can use R-genes that we know phytopthora is going to have trouble overcoming.”

Some of these are being selected from South American solanum species. “There is a good supply out there, a huge diversity. The genes have to be effective against the strains of phytopthora known to be circulating in Europe and we have a handful of candidates that we are working on that are all potentials for stacking with other resistance genes.”

Dr Foster believes that the use of transgenics in potatoes will be part of a combined control strategy. The tools are available; it is the regulatory process that is prohibitively expensive and slows the development down. He expects that growers will have to wait at least five years before commercial varieties would be available, but stresses that it is ultimately dictated by the regulatory system.