Spatiotemporal analysis of Phytophthora infestans population diversity and disease risk in Great Britain

Phytophthora infestans (causal agent of potato late blight) populations are mainly clonal in Great Britain (GB), but sexual reproduction of the pathogen leads to the emergence of novel (non-clonal) genotypes that may have traits such as new virulence or fungicide insensitivity that can make them more challenging to control. In this study, spatiotemporal variation in diversity of P. infestans across GB was mapped and investigated using ArcGIS software. Analysis of >2000 late blight outbreaks during 2006-2018 revealed 169 non-clonal outbreaks in different postcode districts across GB. Statistically significant hot and cold spots of diversity were identified, as well as areas with an increasing trend in the occurrence of high diversity through time. These analyses provide the first quantitative evidence of space-time clustering of non-clonal outbreaks of late blight in GB. The results will be used to guide future efforts to identify the drivers associated with increased genetic diversity of the late blight pathogen and improve management programmes for late blight in GB.