Wild hosts in natural ecosystems also play a critical role in plant pathogen population structure and biology, in particular those with a wide host range and a cosmopolitan lifestyle, as they can harbour sources of pathogen inoculum with a different diversity of genotypes than found in agriculture. There is then potential for (two-way) gene flow across the agricultural / natural ecosystem interface which can have significant consequences for the occurrence of epidemics in both ecosystems, pathogen evolution, wild plant diversity and crop protection. Despite this, ecological and evolutionary studies involving plant pathogens in natural ecosystems and gene flow across the agricultural / natural ecosystem interface is largely neglected.
Recent research investigated populations of the cosmopolitan plant pathogen Sclerotinia sclerotiorum on wild and agricultural host plants. Many different S. sclerotiorum genotypes can be found in fields of carrot, lettuce and oilseed rape but one particular genotype is found at high frequency in all these crops and at different locations. In a ten-year-old meadow and in two consecutive years, the same common genotype was identified on R. acris as found on the crop plants. However, when the S. sclerotiorum population structure was examined in an isolated 'ancient' meadow, a completely different genotype was prevalent. This may suggest local or host specific adaptation by S. sclerotiorum to R. acris. This work has now been published in Plant Pathology 62, 309–324, April 2013.