#Phytophthora tomato free#

The species is thought to originate from Toluca Valley, Mexico, where it infects wild relatives of potato, frequently undergoes sexual reproduction and co-occurs with the two closely related species P. In agricultural systems, sexual reproduction may trigger explosive population shifts that are driven by the emergence and migration of asexual lineages ( Fry et al., 1992, 2009 Cooke et al., 2012). Phytophthora infestans is an extraordinarily virulent and adaptable pathogen ( Fry, 2008 Haas et al., 2009). Late blight remains the most destructive disease of the third largest food crop, resulting in annual losses of potatoes that would be sufficient to feed anywhere from 80 to many hundreds of millions of people ( Fisher et al., 2012). infestans has continued to wreak havoc on potato fields throughout the world. infestans epidemic were due to the absence of chemical and genetic methods to combat it such means became available only several decades later.Įver since triggering the Irish famine, P. Even today, the Irish population remains less than three quarters of what it was at the beginning of the 1840s. The subsequent Great Famine killed around 1 million people, and an additional million were forced to leave the island ( Turner, 2005). The impact of the epidemic reached catastrophic levels in Ireland, where the population was more dependent on potato for their subsistence than in other parts of Europe ( Bourke, 1964 Reader, 2009). infestans finally reached Europe, spreading rapidly from Belgium to other countries of mainland Europe and then to Great Britain and Ireland. infestans, the causal agent of late blight.

#Phytophthora tomato free#

The Spanish introduced Europeans to the South American staple crop potato shortly after their conquest of the New World, but for three centuries Europe stayed free of P. Potato late blight's impact on humankind is rivaled by few other plant diseases. Why US-1 later replaced HERB-1 as the dominant strain in the world is an important question for future studies. now rule out both of these possibilities and show that the lineage that caused the great famine, which they call HERB-1, is clearly distinct from US-1, although they are closely related, and they conclude that both HERB-1 and US-1 might have dispersed from a common ancestor that existed outside of Mexico in the early 1800s. Previously it has been proposed that this lineage was the same as US-1, which was the dominant strain of potato blight in the world until the end of the 1970s, or that it was more closely related to modern strains than to US-1. found that the historical strains all belonged to a single lineage that shows very little genetic diversity.

By comparing the genomes of the historical and modern samples, Yoshida et al. The historical strains were extracted from the leaves of potato and tomato plants that were collected in North America and Europe, including Ireland and Great Britain, from 1845 onwards and stored in herbaria for future research. have used a technique call ‘shotgun’ sequencing to map the genomes of 11 historical strains of P. Phytophthora is thought to have originated in the Toluca valley of Mexico, where many different strains evolve alongside wild potato relatives, but the exact strain that caused the Great Famine, and how it is related to modern strains of the pathogen, has remained a mystery. This disease is caused by a filamentous microbe called Phytophthora infestans, which spread from North America to Europe in 1845, leading to the Great Famine in Ireland and to severe crop losses in the rest of Europe. Few crop failures have been as devastating as those caused by potato late blight in the 1840s.