Genetic analyses of four closely-related plant-pathogenic Phytophthora species

In this research project, we aimed (i) to develop and characterize polymorphic microsatellite markers for analysing the genetic structure of the four Phytophthora species in the P. citricola complex, (ii) to analyse worldwide population structure and pathways of spread of P. multivora, P. plurivora, P. citricola I, and P. citricola ss. using the microsatellites newly devel-oped, and (iii) to investigate the demographic history of P. plurivora in Europe by using coalescent-based methods. Besides providing new genetic markers for additional studies on P. multivora, P. plurivora, P. citricola I, and P. citricola ss., results of this project shall help to better understand the worldwide population genetic structure and dynamics of closely-related Phytophthora species. In addition, the scientific Phytophthora community benefits from the developed microsatellites which shall offer the opportunity for additional population genetic studies.

This project was part of COST Action FP0801: Established and Emerging Phytophthora: Increasing Threats to Woodland and Forest Ecosystems in Europe; working group 1: Invasive potential and Ecology - Expertise and experiments with ecology & spread of Phytophthora.

Within the cosmopolitan plant pathogenic species Phytophthora citricola, high levels of morphological and molecular variation were previously observed. Recently, DNA analyses revealed that the P. citricola complex actually includes four species, namely P. multivora, P. plurivora, P. citricola I, and P. citricola sensu strictu, which show different geographic distributions and host ranges. Unfortunately, because of the lack of neutral, species-specific genetic markers, detailed knowledge on the population genetic structure and possible path-ways of spread of these four Phytophthora species is still missing.