Figure 1.
Disease symptoms caused by, and life cycle stages of, Spongospora subterrane f.sp. subterranea.
Disease symptoms on potato: a) powdery scab lesions. b) root galls. and life cycle stages of the pathogen: c) Sporosorus containing resting spores. d) Single, biflagellate primary zoospore. Bars = 5 µm. Pictures a) and b) taken by R. Lamberts.
Table 1.
Number of Spongospora subterranea f.sp. subterranea samples collected, genotyped and sequenced, sorted by geographical region.
Figure 2.
Inferred phylogeny of Spongospora subterranea f.sp. subterranea and other Plasmodiophorids.
The evolutionary relationship of Spongospora subterranea f.sp. subterranea and other Plasmodiophorids was inferred using the Maximum Likelihood method on the concatenated ITS and actin sequences. The bootstrap consensus tree inferred from 500 replicates is taken to represent the evolutionary history of the taxa analyzed. Branches corresponding to partitions reproduced in less than 50% bootstrap replicates are collapsed. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The number of samples possessing a particular haplotype is given in parenthesis. The underlined haplotypes were detected in the introduced regions Europe (EU), Africa (AF), Asia (AS), Australasia (AU), and North America (NA). tu, haplotypes detected from tuber lesions; ga, haplotypes detected from root galls. GeneBank accession numbers are given for the outgroup species.
Table 2.
Genetic diversity parameters of Spongospora subterranea f.sp. subterranea within the sampled regions, determined using six microsatellite markers.
Figure 3.
Principle Component Analyses (PCA) of Spongospora subterranea f.sp. subterranea multilocus genotypes.
The analyses based on covariances of allele frequencies. (a) PCA performed on individuals resulted in axis 1 explaining 46% and axis 2 explaining 17% of the genetic variation. The dashed lines encircle the two clusters identified by K-means clustering. (b) PCA performed on regions resulted in axis 1 explaining 72% and axis 2 explaining 19% of the genetic variation. The dashed lines encircle regions that are not differentiated based on FST analysis.
Table 3.
Pairwise estimates of FST between sampled regions (above diagonal) and corresponding p-values (below diagonal).
Figure 4.
Global gene flow for Spongospora subterranea f.sp. subterranea and historic dissemination of the potato (Solanum tuberosum).
Estimates were determined among Europe (EU), Africa (AF), Asia (AS), Australasia (AU), North America (NA), and South America (SA). The white arrow indicates estimates of historic gene flow using MIGRATE given as migrants scaled by the mutation rate. Curved black arrows indicate significant recent gene flow between regions inferred by BAYESASS, given as percent of the receiving population. Confidence intervals (5%–95%) are given in parenthesis. Numbered straight arrows represent the historic dissemination steps of potato mediated by human activities; 1) The conquistadors brought the potato to Europe (1567–1593); 2). In the early 1600s, the potato was taken from Europe to Asia; 3) In 1613, the potato was taken from England to Bermuda and from there to Virginia (United States) in 1620; 4 and 5) Further dissemination of potato from England to Southern Africa (1880s), New Zealand (1769) and Australia (1787). Data extracted from historic documents, provided by International Potato Center (CIP), Peru.