Abstract:
Lecanosticta acicola is a pine needle pathogen causing brown spot needle blight that
results in premature needle shedding with considerable damage described in North
America, Europe, and Asia. Microsatellite and mating type markers were used to study
the population genetics, migration history, and reproduction mode of the pathogen, based on a collection of 650 isolates from 27 countries and 26 hosts across the range of
L. acicola. The presence of L. acicola in Georgia was confirmed in this study. Migration
analyses indicate there have been several introduction events from North America
into Europe. However, some of the source populations still appear to remain unknown.
The populations in Croatia and western Asia appear to originate from genetically similar
populations in North America. Intercontinental movement of the pathogen was
reflected in an identical haplotype occurring on two continents, in North America
(Canada) and Europe (Germany). Several shared haplotypes between European populations
further suggests more local pathogen movement between countries. Moreover,
migration analyses indicate that the populations in northern Europe originate from
more established populations in central Europe. Overall, the highest genetic diversity
was observed in south-eastern
USA. In Europe, the highest diversity was observed
in France, where the presence of both known pathogen lineages was recorded. Less
than half of the observed populations contained mating types in equal proportions.
Although there is evidence of some sexual reproduction taking place, the pathogen
spreads predominantly asexually and through anthropogenic activity.
