The 2022 spike in aphid numbers has resulted in a significant impact on the production cycle for seed potatoes, despite populations decreasing since. CPM investigates the steps industry experts are taking to combat the most prevalent potato viruses.
“It’s about creating a robust system which avoids virus infection in the first place.”
By Janine Adamson and Rob Jones
New genetic material with resistance to some of the most prevalent potato viruses may soon be rolling out into commercial breeding programmes, thanks to development work being undertaken by James Hutton Limited (JHL).
As shared at this year’s Potatoes in Practice, held at Balruddery Farm in Dundee, delegates learned of pipeline developments from the commercial arm of the institute. Speaking ahead of the event in an exclusive preview interview for CPM, potato breeder Drummond Todd says the uplift in potato virus in recent years has meant breeding programmes have had to widen focus.
“In 2022 we experienced huge aphid pressure therefore many growers observed an increase in virus – most strikingly potato leafroll virus (PLRV) – in seed crops the following year. This is because the symptoms you see in the subsequent year are a ‘secondary’ result of the ‘primary’ infection.
“Although aphid numbers have been substantially lower in 2023 and 2024, due to the length of the production cycle for seed potatoes, that spike will have a significant impact for a number of years. Furthermore, virus pressure will continue to be high as a consequence of increased reservoirs of virus in crops and groundkeepers,” explains Drummond.
But, it’s not all doom and gloom, he adds. Research has been taking place to validate new genetic markers for resistance to potato viruses using molecular diagnostics, similar to the previous work undertaken for late blight and potato cyst nematode resistance at the institute.
In fact, the team at JHL and JHI (James Hutton Institute) are validating markers for two different sources of PVY resistance and are working on potential candidates for PLRV resistance. According to Drummond, populations have been produced and material is already in the field ready for testing.
“If successful, the markers will then be applied in commercial breeding programmes which is ultimately what JHL is about – commercialising the outputs from science. However, it’s important to stress that this work is about progression.
“We have to produce viable varieties so are seeking parental material with solid agronomic and sensory performance together with old and new resistance markers, rather than combat potato virus in isolation. By building and stacking in this way, we can maintain and increase the marketable yield of new varieties,” he says.
Drummond hopes JHL’s breeding work will help to increase confidence in the future of Scottish seed crops, after a challenging year of downgrades. “There’s a full awareness of the size of the problem among growers, we’re likely to be looking at continued restriction in seed potato availability in the coming season.”
Adding a practical, agronomic perspective to the presentations at Potatoes in Practice, Graham Tomalin from VCS Potatoes says when it comes to ware crops and potato virus, there doesn’t seem to be a clear pattern. In another exclusive preview interview with CPM, he explains the impact of potato virus varies depending on the specific variety, type/virus combinations, and time of infection.
“Virus and combinations of viruses can cause splitting and tuber deformities in some varieties. The same virus or virus combination can infect other varieties and exhibit no tuber symptoms. It’s very nuanced, meaning in-depth knowledge of the variety is very important.”.
Graham says he’s noticed an increase in PLRV in UK crops this season, whereas PVY levels remain similar to last year. “Although awareness is there, growers tend to revert to their agronomist where virus occurs. However, it’s about creating a robust system which avoids virus infection in the first place which all starts with seed sourcing. The yield impacts of virus infection in some varieties can’t be overlooked.”
With the promising developments coming through from Drummond and JHL, Graham hopes potato virus will eventually be managed through genetics and targeted breeding. Although he warns that such progress has to result in varieties that match or exceed current yields, plus deliver marketable traits such as skin finish and processing attributes.
In the meantime, he highlights the importance of purchasing input stock of the highest possible quality. “With shortages across the board this hasn’t been the easiest of late, but buying seed of the lowest generation and highest certification grade is the most effective way of minimising the risk of potato virus. A good long-term relationship with seed suppliers is important.
“Where I advise in East Anglia, aphid populations in most years are particularly high as is the prevalence of virus in volunteers. This makes quality seed sourcing imperative,” he stresses.
For seed growers he adds how location can add further complications, whether that be proximity to ware potato fields or the presence of volunteers in other crops being a virus source. “You also can’t risk growing near to allotments or residential veg patches. This means you’re often utilising land without irrigation which creates additional production challenges in a relatively dry area of the country,” explains Graham.
But again, even when deploying tried and tested cultural control mechanisms, it’s not always simple, he adds. “Earlier planting would be a way to reduce virus impact because plants gain a level of resistance to some viruses as they develop. But of course, we’re finding this is becoming more challenging to achieve with recent weather patterns and earlier aphid flights.
“In addition to all of the above, you also have to reduce the risk of virus spreading in seed crops by using chemical control options – whether that be oils or insecticides.”
Earlier this year an emergency approval was granted for paraffin oil product Olie-H in seed potato crops, for application from tuber initiation onwards. The product works by coating the crop’s leaves with a thin film which disrupts the acquisition and transmission of virus by the aphid’s stylet.
Used alongside translaminar insecticides such as Teppeki (flonicamid) and InSyst (acetamiprid), Olie-H forms part of an integrated approach but offers a completely different mode of action, says Graham. He adds that it should be noted the use of Teppeki is restricted in many ware markets.
Graham also believes more work can be done to maximise the cultural control methods which are becoming popular in other areas, such as companion cropping. Most famed for use in oilseed rape to combat cabbage stem flea beetle, he says trial work is taking place which looks at planting a spring cereal alongside seed potato crops.
“By shielding the young potato crop, it makes it more difficult for the winged aphid to locate the plants because they’re unable to differentiate the potato plant from the background cereal crop. This is similar to research that’s taken place in sugar beet and carrots.
“Work has also been undertaken, with promising results, looking at a similar concept with straw mulches. But I can’t see this taking off in East Anglia in the same way due to the volume of rented land and implications of resistant blackgrass seed spread.”
This article was taken from the latest issue of CPM. Read the article in full here.
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