From a European to a Global Database of Phytophthora infestans Genetic Diversity: Examining the Nature and Significance of Population Change

Understanding genetic diversity and the evolutionary forces that shape populations of Phytophthora infestans is of great scientific interest and has practical implications on the success of short and long-term strategies of disease management. Typically, populations of P. infestans have comprised localized sexual populations yielding oospore progeny from which limited numbers of highly successful clones have emerged. Such clonal lineages may dominate crops on a regional to global scale for decades until their eventual displacement by new clonal lineages. Gaining a detailed view of the mechanisms and processes behind such transitions has been challenging but these are exciting times in Phytophthora research and new insights are emerging on several fronts. The explosion in P. infestans sequence data culminating in the draft genome sequence has proved a valuable source of genetic markers to study populations. Neutral Simple Sequence Repeat (SSR) markers are proving powerful tools for understanding the population structure at scales from single plants to whole continents and examples of such studies will be discussed. Rapid progress in understanding key functional genes associated with pathogenicity or virulence is allowing us to examine their evolution on a population scale and the example of avr3a gene diversity in Great Britain (GB) is discussed. Such data will be crucial in successfully exploiting new sources of host resistance. In an increasingly global industry we share the practical problems in disease control; relying on the same options of managing primary inoculum and making the best use of host resistance and fungicides. The effectiveness of such control strategies will be influenced by changes in the pathogen population and it is thus important to understand population change on local and wider geographical scales. The EUCABLIGHT project was established to meet such a need and a comprehensive database of P. infestans diversity across Europe with data on almost 20 thousand isolates from 22 countries has been compiled. The background, mechanisms and advantages of this approach are presented in the context of contemporary changes in P. infestans lineages in some European populations. The database has recently been widened to include Central and South America and further expansion is planned.