Potato Review

www.potatoreview.com POTATO REVIEW MARCH/APRIL 2022 55 BLIGHT T HE first case of the 41_A2 late blight genotype that emerged in Denmark in 2013 was detected in a crop of Maris Piper grown in Fife last August. The news was described as evidence of the value that genotype testing until now funded by AHDB Potatoes provides to growers. Speaking at the Scottish Agronomy potato conference held online on last month, Dr David Cooke, research lead in Cell and Molecular Sciences at the James Hutton Institute and co-ordinator for the EuroBlight potato late blight monitoring project, explained that the genotype was detected during routine sample analysis. There is no indication of its source, but human activity would be the likely cause given that regulations in Scotland mean only home-grown seed can be planted. “The alternative windborne route would involve about a 700-kilometre journey from mainland Europe against the prevailing airflow,” David said. Eric Anderson, Scottish Agronomy Senior Agronomist, agreed that the distance to Late blight discovery: New strain raises some questions and highlights the value of monitoring. known source of infection in Scandinavia or the Netherlands meant airborne spread was highly unlikely. “It’s almost certainly human interaction of some kind but we should not discount the possibility that it spread from a tomato plant to a potato crop,” Eric said. The 2021 season was another atypical year for late blight (Phytophthora infestans) with the cold spring delaying the first cases of disease. As a result outbreaks in Scotland were later than average and in south-east England, they appeared to be highly localised. “The first positive sample for Scotland was not until July 15th and was found in Angus while in England it was found in Kent on May 26th. In total, 210 outbreaks were reported, this is up significantly on the 94 confirmed in 2020,” David said. During the 2021 season the James Hutton Institute received 1,700 samples for testing with 1,170 successfully genotyped. Of the very broad 86 varieties involved, the three mostly commonly sampled were Maris Piper, King Edward and Melody. “The level of activity was up considerably on the previous year, and we are grateful to the 67 blight scouts who diligently and studiously submitted samples from across England, Scotland and Wales. Over the years this project has run, Blight Scouts have been central to furthering our knowledge and understanding of late blight dynamics in the UK and further afield,” David said. The emergence of 41_A2, which had spread to six other European countries by 2020, is likely to prompt many questions from growers, Eric said. The finding in Fife is unlikely to be the only incursion to Great Britain. Analyses by a consortium of EU researchers, suggests that it has a high level of aggressiveness towards susceptible potato cultivars and from Estonia we know that 41_A2 exhibited some insensitivity to fluazinam. Isolates from the Danish population in one season had a significantly shorter latent period, suggesting geographic adaptation. ➜ “In total, 210 outbreaks were reported, this is up significantly on the 94 confirmed in 2020.” Dr David Cooke, Researcher Dr David Cooke Eric Anderson