EuroBlight – an organization that is continuously examining the ongoing evolution of the European population of the potato late blight pathogen – has unveiled its latest report on the 2018 results. Approximately 1,000 samples were genotyped from 22 countries during the study.

Since its arrival in the nineteenth century, Phytophthora infestans, the cause of potato late blight, has remained a serious threat to European potato production. Although we are now better equipped to control the disease than in the past, evolving pathogen populations continue to challenge integrated management practices. Rapid changes in P. infestans populations causing late blight in Europe, America and Asia, including the emergence of strains with increased aggressiveness or reduced fungicide sensitivity, have been observed.

Therefore, coordinated and continuous pathogen monitoring was proposed by the EuroBlight consortium at its meeting in 2013 and is now implemented as an EU-wide monitoring activity, including all stakeholders. The organization continues to monitor populations and characterize the invasive genotypes to help optimize IPM strategies, as required by EU Directive 2009/128/EC on the sustainable use of plant protection products.

According to EuroBlight, disease pressure in 2018 was relatively low due to the hot dry weather across much of the season. Nonetheless, 17 partner organizations collected 1074 samples from 24 European countries. Included also is data from partners in the IPMBlight2.0 project, which generates pathogen phenotype data to support IPM strategies. The genotype data from 2013-2018 now comprises over 8000 samples from 34 countries. Support of international groups also generated data for parts of Asia, South America, and North Africa.

Over the last six years, 60-79% of the sampled population comprised known clonal lineages that recur each season. The remaining samples were novel, genetically diverse genotypes found at a single location in one season and grouped in a category termed ‘Other’ (Figure 1).

Figure 1

In 2018, clone EU_13_A2 (blue-13) remained the most frequently sampled and widespread genotype with 25% of the samples from 10 countries. The distribution of this aggressive clone EU_13_A2 with its resistance to metalaxyl continues to affect management efficacy in Europe, parts of Asia and North Africa, reinforcing the need for pathogen data to support IPM best practices. The frequency of EU_6_A1 at 13% was the lowest it has been in six years and localized to France and the UK. Similarly, the frequency of EU_1_A1 further decreased from 2.2 to 1.6% of the population.  A progressive displacement of these three lineages is occurring (Figure 1).

Despite the warm dry weather, three newer clones (EU_36_A2, EU_37_A2, and EU_41_A2) increased in frequency in 2018. EU_36_A2 was first sampled at low frequencies in the starch potato areas in Germany and the Netherlands in 2014 and had spread across the Netherlands into Belgium, the UK, Denmark and Poland by 2017. In 2018 it was also sampled on crops in Spain, Hungary, and Serbia and made up 16% of the samples (up from 10% in 2017).  Genotype EU_37_A2 was first detected in Noordoostpolder in the Netherlands in 2013 and had become established in England, Belgium and northern France comprising 14% of the samples by 2017.

The EuroBlight model of pathogen tracking is a rapid, cost-effective and coordinated approach to understanding pathogen evolution on a European scale. Data on the dominant clones have been passed to growers, advisors, breeders and agrochemical companies to provide practical management advice and shape longer-term strategies. The data provide an early warning of the incidence and spread of novel clones that are enabling a timely response from the industry.

Among the companies and institutions that participated in the sampling are AHDB Potatoes, BASF SE, Bayer CropScience AG, Belchim Crop Protection, Dupont de Nemours, Emsland Group and many more.