Abstract
Spongospora subterranea f. sp. subterranea (Sss) causes two diseases on potato (Solanum tuberosum), lesions on tubers and galls on roots, which are economically important worldwide. Knowledge of global genetic diversity and population structure of pathogens is essential for disease management including resistance breeding. A combination of microsatellite and DNA sequence data was used to investigate the structure and invasion history of Sss. South American populations (four countries, 132 samples) were consistently more diverse than those from all other regions (15 countries, 566 samples), in agreement with the hypothesis that Sss originated in South America where potato was domesticated. A substantial genetic differenciation was found between root and tuber-derived samples from South America. Estimates of past and recent gene flow suggested that Sss was probably introduced from South America into Europe. Subsequently, Europe is likely to have been the recent source of migrants of the pathogen, acting as a “bridgehead” for further global dissemination. Quarantine measures must continue to be focussed on maintaining low global genetic diversity and avoiding exchange of genetic material between the native and introduced regions. Nevertheless, the current low global genetic diversity of Sss allows potato breeders to select for resistance, which is likely to be durable.
Highlights
There have been many deliberate or accidental anthropogenic introductions of organisms beyond their original geographical ranges [1]
Phylogeny We used the concatenated nucleotide data from the actin and internal transcribed spacer (ITS) region to reconstruct the phylogenetic relationship of subterranea f. sp. subterranea (Sss) and other Plasmodiophorids
CHap6 was found in all introduced regions and accounted for 96% of haplotypes found in these regions
Summary
There have been many deliberate or accidental anthropogenic introductions of organisms beyond their original geographical ranges [1]. Many important crops have been intentionally taken from their regions of origin and introduced to other suitable environments around the world, because of their value in food and fiber production [2,3,4] These introductions have often been accompanied by unintentional introduction of plant pathogens. Increasing global trade in plant products carries the danger of introduction of pathogens, providing recurrent opportunities for new invasions [5,6,7]. These pathogens have the potential to cause severe economic losses to crops, ornamental plants, or forests, and can lead to severe problems in human or livestock nutrition [8,9]. Once introduced in Europe, P. infestans was distributed worldwide via the international seed potato trade
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