Archives for posts with tag: Phytophthora infestans

We eat a lot of potatoes in our house.  Having a vegetarian and meat-eater in the house can make mealtimes stressful, but baked potatoes topped with broccoli for me and bacon for him makes us both happy.  I kid, but in early nineteenth century Ireland potatoes were no joke… they were the staple food for the lower class, the landless laborers.

Existing dependent on a single food source is risky and in 1845 a plant disease epidemic took out the potato in Ireland (in the field and in storage).  The disease would later be named late blight and is regarded as the disease that birthed the study of plant pathology.   The causal agent of late blight is a Phytophthora infestans (Latin for “plant destroyer”), fungal-like organism called an oomycete.  As a result of this microscopic killer, an estimated 1 million Irish starved and another 1.5 million emigrated from Ireland, dramatically changing not only Ireland but countries like the United States that received the displaced.  Late blight remains a significant threat to potato and tomato industries today (2009 epidemic in Northeast US); however, we now have management options such as fungicides and moderately resistant varieties to minimize losses.

Potato with late blight (foreground); Potato treated with fungicides (background)

Potato with late blight (foreground); Potato treated with fungicides (background)

(Image: Courtesy D. Inglis via

Last week, Yoshida et al. (2013) released a study identifying the specific strain (or genotype) of P. infestans responsible for the Irish Potato Famine. Researchers isolated samples of the pathogen from preserved potato leaves with late blight symptoms and compared them to modern strains with DNA analysis.  Genotype HERB-1 was consistently isolated from the historic Irish samples, suggesting it was the strain responsible for the late blight epidemic.  HERB-1 is different from modern genotypes and is likely extinct, having been replaced by US-1 by the 20th century, as the predominate genotype outside of P. infestans center of origin (Mexico).  Researchers also note that while US-1 and HERB-1 are related, US-1 is not a direct ancestor of HERB-1.

I think one of the most interesting parts of this study was the use of preserved herbarium samples to generate the dataset.  Just think of other pathogen populations and histories that could be elucidated using this approach!  Aside from the cool factor, understanding how these pathogens evolve is vital for developing new management strategies.

 PS – For more on late blight click here.


Happy Friday!  Here are the stories I’ve been reading this week…

1. Amphibian plague

The fungus Batrachochytrium dendrobatidis (Bd, the chytrid fungus) is the causal agent of chytridiomycosis, a fatal disease of frogs.  In the May 2013 issue of EcoHealth, Grower et al. report that Bd can also infect and kill a limb-less, snake-like group of amphibians called caecilians in the wild.  Unless you’re an avid caecilian enthusiast (they’re out there), you may be wondering ‘so what’.  Adding more species to the Bd-susceptible list is notable because some researchers are hypothesizing that this fungus may cause disease in ALL amphibians.  Imagine a pathogen with the ability to infect all mammals.  The chytrid fungus has already been blamed for the extinction of nearly 300 amphibian species.  Furthermore, knowing Bd infects the soil-dwelling caecilian suggests that the pathogen is adept in soil survival.  It was previously known that Bd survives and is spread via water, thanks to its swimming zoospore.

caecilian, Natural History Museum via Natural History Museum via

2. Cal State leaning toward virtual labs?

Officials at the California State University system are trying to solve the problem of “bottleneck courses”; those that difficult for students to get into, thus slowing their advancement or even causing them to drop out.  Some of these identified courses are required lab-based science courses for non-majors.  One solution may be to enroll students in virtual lab classes, involving simulations of experiments.  On one hand, this alleviates the bottleneck issue while still providing students with exposure to basic theories, problem-solving, scientific method, etc.  However, as Cal State professor Jeffery Bell cautions, the virtual lab may be too abstract for some students and give them a false appreciation of what scientists really do.  I have to agree and I’d hate to see lab sections for non-majors completely eliminated in favor of simulations.  There’s a “cool” factor to science (preparing a specimen and observing it under a real microscope, for example), that doesn’t quite translate to viewing something on a computer.

3. The Case of the Irish Potato Famine

I’m planning to write more about the Irish Potato Famine next week since it’s one of the great historical plant pathology stories (yes, we have those).  While the causes of the Irish Potato Famine are political as well as biological, it was announced this week that the particular strain of Phytophthora infestans, the pathogen responsible for destroying millions of potatoes in 1840’s Ireland, has been genetically identified.  This strain, known as HERB-1, was responsible not only for the deaths of an estimated 1 million people but also immigration of many Irish to the United States and other parts of Europe.  More next week…