![]() infestans from a sexually reproducing population in Mexico (shown by black triangles). Since then there have been at least three major migrations of P. mirabilis (a pathogen that does not infect potatoes) are thought to have diverged from a common ancestor about 1200 years ago. Schematic representation of the time-line for the emergence of major lineages of Phytophthora infestans, the pathogen that causes late blight in potatoes, as proposed by Burbano and co-workers ( Yoshida et al., 2013). It will be interesting to figure out what happened between 1900 and the 1970s, when new populations began to displace US-1 in Europe ( Figure 1). Moreover, it should be possible to use the newly obtained DNA sequences to develop markers that allow 20 th century samples to be tested for the presence of HERB-1. infestans populations are still being observed today with, for example, the aggressive genotype 13_A2 displacing other genotypes across Europe over a period of less than three years ( Cooke et al., 2012), and the rapid emergence of genotype US-22 in the eastern USA in 2009 ( Fry et al., 2013). The new work also emphasises the threats associated with the movement of pathogens between continents, and highlights the occurrence of waves of pathogen migration and genotype displacement. propose that HERB-1 and US-1 emerged from a metapopulation that was established outside of Mexico in the early 19 th century and that US-1 displaced HERB-1 at some point in the 20 th century ( Figure 1). infestans diversity in the world, but Yoshida, Schuenemann et al. Analysis of both mitochondrial and nuclear DNA showed HERB-1 and US-1 to be sister groups in a clade distinct from contemporary genotypes. It has not been observed in modern times, but is clearly a close relative of US-1. infestans was responsible for the first global migration of the pathogen in the 1840s, and then persisted for at least 50 years. ![]() They found that the pathogen strains in all samples were representatives of a single lineage, which they have called HERB-1. infestans from 11 infected leaf samples that were gathered in Ireland, Great Britain, Germany and Canada between 18 ( Yoshida et al., 2013). Now, Burbano and co-workers-including Kentaro Yoshida of the Sainsbury Laboratory and Verena Schuenemann of the University of Tübingen as joint first authors, plus colleagues at other centres in Germany and the US-have sequenced the genome of P. However, this idea was challenged when researchers at North Carolina State University identified a different type of mitochondrial DNA in herbarium samples of potato late blight collected between 18 ( Ristaino et al., 2001). This lineage was defined by nuclear DNA markers and, crucially, a mitochondrial haplotype termed Ib, and the Cornell team proposed that it had emerged from Mexico in the 1840s to cause severe crop losses on a global scale ( Goodwin et al., 1994). infestans, dubbed US-1, which was identified in 13 countries on four continents. Work in the 1990s by researchers at Cornell University revealed a dominant lineage of P. Now, more than 160 years later, Hernán Burbano of the Max Planck Institute for Developmental Biology and co-workers have combined the power of next-generation sequencing technology with the availability of herbarium samples to peek through a 50-year window of history at the genome of the pathogen that contributed to so much human suffering ( Yoshida et al., 2013). As such, it has been credited with establishing the field of plant pathology, and is a major milestone in the foundation of epidemiology as a scientific discipline. The water mould Phytophthora infestans was first identified as the probable cause of late blight by Miles Joseph Berkeley in 1846, almost 20 years before Louis Pasteur formally proposed the germ theory of disease. ![]() Emerging in the mid-1840s, the disease rapidly became pandemic, precipitating the Great Famine, which led to almost a million deaths in Ireland and the emigration of many more, plus considerable loss of life and extreme political upheaval throughout mainland Europe ( Zadoks, 2008). There can be few diseases of plants that have had a more profound effect on human health, society and politics than potato late blight. infestans has spread around the world from Mexico since the 1840s The rise and fall of the Phytophthora Infestans lineage that triggered the Irish potato famine. Related research article Yoshida K, Schuenemann VJ, Cano LM, Pais M, Mishra B, Sharma R, Lanz C, Martin FN, Kamoun S, Krause J, Thines M, Weigel D, Burbano HA.
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