The team, from the James Hutton Institute (JHI), the Sainsbury Laboratory and other partners, used DNA-based forensic analysis to map how these more virulent forms have rapidly displaced other genotypes in Europe. In Britain, the new lineage has grown to make up more than three-quarters of the disease population in less than three years, they found.
Lead researcher Dr David Cooke of the JHI said of the highly variable 13_A2 lineage: "It is more difficult to control due to a combination of increased aggressiveness, an ability to overcome some sources of cultivar resistance and its resistance to a key fungicide."
He added: "Growers must remain alert. In a very wet summer, any weakness in the control strategy is exploited by the pathogen, resulting in severe crop losses."