Their finding comes from assessing the spread and virulence of the pathogen responsible for potato late blight, Phytophthora infestans , the pathogen behind the Irish potato famine which became a serious threat again in the UK in 2011.

Rothamsted Research reports: “In the UK, potatoes are second only to wheat in national economic importance, and emergence of the pathogen’s increased virulence in 2011 prompted funding for the latest research, which is reported today in Proceedings of the Royal Society B.”

Fungicides and resistant cultivars were chosen as disease control methods as these are the most commonly and easily applied, explained Kevin Carolan, a pathogen evolution modeller at Rothamsted Research, which led the project with Fera Science, Scotland’s Rural College and ADAS.

“Pathogens such as blight evolve virulence, thwarting the resistance genes bred into the potato,” Kevin told the Rothamsted Research website. “We have shown that appropriate use of fungicides can slow this evolution, so the resistance genes are more durable, preventing loss of disease control.

“Some farmers already use more than one method to contain disease within their crops; they may use cultivars with one or more resistance genes but still apply fungicides for peace of mind,” he added. “Our research provides evidence for such an approach, and for similar approaches using a combination of other methods, and indicates how the timing and degree of dosing, for instance, will affect resistance to disease.

“We’ve shown that certain doses of fungicide will accelerate the evolution of virulence in the pathogen, making the problem worse, and other doses will slow the evolution of the pathogen protecting genetic resistance in the cultivars.”

Many growers apply a dose to control the pathogen for only that season, he explained. “Our finding will help agronomists and advisory boards to develop a toolkit for designing the best dose to apply to a given cultivar, such as Cara or King Edward, that will not only provide immediate containment of the pathogen but also slow its evolution, so controlling the disease for generations to come,” he added.

He stressed that the finding represents a general technique to maintain the effectiveness of cultivar resistance. Combining other methods of disease control could also reduce the growth rate of epidemics, says Rothamsted Research, including methods such as biological control organisms, changes to soil fertilisation levels or agronomic measures, such as planting date, planting density and intercropping.

For further information:

• Read the full story on the Rothamsted Research website here
• Read the abstract or the full paper (registration required) on the Proceedings of the Royal Society B website here