PotatoPlus

At TSL, we operate on the principle that it is better to protect crops with biology rather than chemistry. Potato late blight, the biotic cause of the Irish Potato Famine in the 1840s, still causes major losses to potato production. Most commercial potato varieties can't detect the late blight pathogen, Phytophthora infestans, allowing infection to spread and destroy fields of crops within weeks. With such high risks,farmers rely on regular preventative fungicide sprays to protect their potato plants – up to 15 applications per growing season.

“If you have a potato that is inherently resistant to disease and shows reduced post-harvest losses, which will need less pesticides – to me, that’s obviously a good thing.” - Professor Jonathan Jones

Can R genes reduce the need for fungicides?

There are many reasons for preferring genes to chemicals to protect our crops. Although improvements in fungicide formulations and spray regimes are currently effective, these need to be continuously adapted as new pathogen strains evolve to become insensitive or resistant to the chemicals. Reduced spraying also means fewer tractor journeys are required, lowering carbon dioxide emissions and soil compaction. There is also less selection for pathogen genes linked to drug-resistant fungal diseases in humans, and less damage to beneficial fungi in the soil.

Discovering R genes in potato and its wild relatives

For the last 25 years, researchers at TSL have been looking for novel Resistance to Phytophthora infestans (Rpi) genes against late blight in wild relatives of potato and have found several. From knowledge of what they recognize in the pathogen, we can prioritise those immune receptors that detect the most conserved and widespread molecules found in every race of the pathogen.

Our project to improve potato disease resistance has a long history. We isolated Rpi-vnt1 from the potato relative Solanum venturii in 2009. More recently we isolated Rpi-amr3 and Rpi-amr1. With collaborators in Poland, we have also isolated Ry_sto, a potato gene that confers resistance to Potato virus Y (PVY). We have also isolated a potato gene called Rl _adg that confers resistance to potato leaf roll virus (PLRV). Potatoes that carry the three Rpi immune receptors are resistant to multiple races of the late blight pathogen, and this resistance is highly likely to be durable. Their resistance to PVY and PLRV will mean it will be much easier to produce seed potatoes in England, with fewer insecticides applied to restrict PVY and PLRV transmission by aphids.

R gene delivery via soil bacterium

Once we identify new R genes, how do we get them into our potato varieties?
We have a nature-based solution for adding genes to potato (and other plants). The soil bacterium Agrobacterium can be used to add useful genes (and no others) to any plant. This is particularly useful in potato, where genetic crosses always disrupt the combination of properties that makes the original variety desirable. Thus, we can add useful genes for disease resistance to the popular UK variety Maris Piper without changing any of its other properties.

Maris Piper + Resistance = PiperPlus

PiperPlus 1.0
Maris Piper potato with our three Rpi genes plus sequences that improved tuber quality, and with a tomato gene that enabled us to select for those plant cells that receive the specified DNA.

PiperPlus 2.0
When we realized PiperPlus 1.0 is susceptible to Potato Virus Y, we generated a successor line that also carried the Ry_sto gene, and designated that line PiperPlus 2.0.

Precision Breeding

The Precision Breeding (Genetic Technologies) Act 2023 enables plant varieties to be developed using modern biotechnology and marketed in England with a reduced regulatory burden relative to crops classified as GMO, provided that the properties of the variety could plausibly have arisen as an outcome of traditional breeding methods.

This includes small changes in the genetic sequence (e.g. gene editing) of a plant or adding genes from close plant relatives that could have been added with conventional breeding methods (e.g. cisgenics).

The Advisory Committee on Releases to the Environment (ACRE) reviewed whether PiperPlus 1.0 could be considered a “Qualifying Higher Plant”, a preceding term for “Precision Bred Organism (PBO)” used by Defra for research regulations while market regulations were being developed.

Based on their review, ACRE provided advice on which genes and genetic changes could have been feasibly introduced using traditional breeding methods. They were satisfied that the resistance genes from Solanum venturii could be introgressed based on published evidence that it already been done and proposed that the same would be feasible for S. americanum.

PiperPlus 3.0

Some of the sequences associated with tuber quality and selection markers in PiperPlus 1.0 were seen as less likely to be added via traditional methods as described by the Act. To develop a variety that would qualify as a Precision Bred Organism (PBO), the Jonathan Jones group excluded tuber quality traits in PiperPlus 3.0 and rebuilt the DNA construct, placing R genes in a new vector that can accommodate larger fragments of DNA. The construct also carries a potato selectable marker gene (StCS^R) instead of the previous tomato gene.

Get ready for PiperPlus & CharlottePlus

We are now introducing this set of genes into several UK-favoured potato varieties, beginning with Maris Piper and Charlotte. The new varieties, PiperPlus 3.0 and CharlottePlus, will be brought to market in England by our commercial partners BioPotatoes once we receive approval under the PBA.

These lines will have many advantages:

• They will be completely resistant to all the late blight races currently circulating in the UK, reducing the need to spray for late blight control (though some sprays may still be needed against early blight, a different disease).
• Their resistance to PVY and PLRV will mean it will be much easier to produce seed potatoes in England, with fewer insecticides applied to restrict PVY and PLRV transmission by aphids.
• These virus vectors are more prevalent in warmer climates; for this reason, the British seed potatoes are usually produced in Scotland. However, over half of the GB potatoes are grown in East Anglia and Yorkshire. PiperPlus 3.0 and future virus-resistant lines will enable seed potato production in England.
• Seed potato production in England will further reduce CO₂ emissions and costs from transportation of seed potatoes from Scotland to growing areas in England.

“We’ve been able to integrate so many excellent qualities within the Maris Piper that could greatly benefit our environment and our people.” says Dr Agnieszka Witek, who leads the PotatoPlus work in Jonathan's lab, “Developing an even better Maris Piper or Charlotte and potato for the UK is something we would love to to achieve.”

What is happening in 2025?

We produced many potential varietal lines of Maris Piper and Charlotte carrying the resistance genes and tested them in the field in Norwich in summer 2024. The best of these lines will be assessed for yield and other traits at NIAB in Cambridge in summer 2025.

We have produced in the last 12 months >100 additional lines of Maris Piper and Charlotte that will be evaluated in the field in Norwich this summer. We are confident that from this and last year’s field evaluation, we will identify “the line” for each variety that can be brought to market as PiperPlus or CharlottePlus.