Abstract
Phytophthora infestans is among the most destructive of plant diseases. Pathogen populations have varying degrees of host preference among potato and tomato, from no specificity to extreme specialisation. How host specificity impacts fitness among populations is unclear. Comparing the aggressiveness of both population types can shed light on the determinants of host specificity in P. infestans. A trade-off between generalism and quantitative aggressiveness can explain the variation among strains. I assessed the existence of such a trade-off by analysing the global cross-inoculation data on potato and tomato isolates, and tested whether specificity has changed over time. The synthesis included 44 and 34 data points for potato and tomato isolates respectively. Potato isolates overall did not prefer their original host significantly more than tomato isolates. However, tomato isolates became more generalist over the last few decades. High specificity was associated with significantly greater aggressiveness, and strains from potato can generally infect tomato with similar aggressiveness and specificity as in reverse. This synthesis reveals several novel insights on the evolutionary ecology of the blight pathogen, and provides a new way to map and track P. infestans populations. Many unresolved questions on host specificity and aggressiveness remain which are discussed.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Conflict of Interest: The sole author declares there is no conflict of interest.