Why the Irish Potato Famine was not caused by a fungus

During the long, wet summer of 2012 (perfect late blight weather!), I gave a short public talk about the potato and late blight as part of the Taste of West Cork Festival in Skibbereen, Co. Cork.

The panel of speakers also included the excellent and informative broadcaster Éanna ní Lamhna (of RTE radio fame) who spoke about the history of the potato as well as the history of the Irish potato famine.

Despite the argument that political and economic issues had a great role to play in the Irish potato famine, there is no doubt that the loss of the potato crop due to late blight was the trigger that started it all.

Late blight was, and is, caused by the plant-pathogenic organism Phytophthora infestans which, unfortunately, many people describe as a 'fungus'.

Éanna ní Lamhna described it as such during her talk and I, humorously and good-naturedly (I think!), pulled her up on it. As you can imagine, given that much of the audience had come to see and hear the delightful Ms. ní Lamhna and not some young upstart like me, I had to thread very carefully and there was much friendly banter.

Speakers at the 'Humble Spud' talk

You can't blame anyone for making the mistake - P. infestans is often described as a fungus by those who really should no better.

Browsing through the excellent Atlas of the Great Irish Famine (Cork University Press) recently, I noticed the disease-causing organism is described in several places therein as a 'fungus'.

In a news report in a January issue of the journal Nature, P. infestans was described as "an organism similar to, and often grouped with, fungi". If the author meant that it is often grouped or lumped-in with fungi on a casual (and incorrect!) basis, she's quite right, but as we now know, the organism is not grouped (i.e. classified) as a fungus by fungal taxonomists.

The minutiae of fungal taxonomy is not something we should get bogged down in here (although some would argue that that boat has sailed!), but P. infestans is classified as an oomycete and can be found in the same kingdom as the brown algae and diatoms. Although it may have started out in the Fungi kingdom, it is now firmly categorised as a 'fungal-like organism'.

Damage caused by late blight of potato (APSNET)

A letter in this week's issue of Nature, taking issue with the original news report, states: "It was Anton de Bary, the father of mycology, who coined the genus name Phytophthora ('plant-destroyer') and classed the pathogen as a fungus. But modern molecular sequencing indicates that his interpretation was incorrect"

"The organism is actually an oomycete, a pseudo-fungus that evolved from killer ancestors in the ancient oceans and not from wood-degrading fungi", concluded the author.

Within mycology (the study of fungi), there is some debate over the use of the term fungus. While none would argue against the weight of molecular evidence that clearly puts P. infestans outside the Kingdon, some would argue that, since they are of interest to mycologists and they share many of the common morphological features of fungi, a broader defintion of the term is required.

Money (1998) has argued that the term fungus should have two distinct meanings: (1) the strict taxonomic name used to describe organisms from the Kingdom Fungi and (2) a practical reference to organisms studied by mycologists that share similar characteristics to fungi.

Somehow, I think the taxonomists would disapprove, and so would I.

I'll have two killer whales and a bottle of milk please...

The idea of adding a barcode to a product in a shop for making the life of a checkout operator easier is one of those inventions which we now hardly think about but has revolutionised the way we shop.

Retailers no longer need to price every individual item but need only place one large display price for the consumer to refer to. It makes things easier for the consumer too, knowing that we will almost certainly not be overcharged at the till due to a human error.

Barcodes were originally developed for labelling railroad cars but only took off when supermarkets saw their advantages and began to use them widely. It was two Americans, Bernard Silver and Joseph Woodland who patented the technology in 1949 and described both the linear type of barcode which we are still familiar with, as well as a 'bullseye' circular design.

However the two men were ahead of the technology available to them at the time, with IBM reporting that while the idea was very interesting, the technology to process the information wasn't yet available in the early 1950's. It wasn't until the early 1980's that the technology began to be rolled out in supermarkets across the US. Unfortunately, Bernard Silver never got to see the success of his invention as he died in a car crash in 1963.

Nowadays, barcoding has become almost universal. Sitting at my desk, I can see that my computer is barcoded by the manufacturer and contains a unique product number. Internally, most of the components from the disk drive to the memory is all barcoded for ease of tracking.

If I decide to take a break later, I can drive to the supermarket in a car which is barcoded and pick up a barcoded lunch. I can pay for my barcoded sandwich and barcoded chocolate bar at the self service checkout, where I get to scan my own barcoded product, as well as my unique supermarket loyalty card. This allows the supermarket to record what I like to purchase and target marketing at me specifically.
Going back to the office, I could pop into the library where my unique membership card will be scanned along with the books I want to borrow. In short, my whole life is a series of barcoded events. From airline tickets to identity cards, the conspiracy theorist could have a field-day.

Some of the uses to which barcodes are now put would surely surprise the original inventors. Scientists currently meeting in Mexico City at the 3rd International Barcode of Life Conference are putting the finishing touches to an agreement which aims to give every organism on Earth a unique barcode based upon its genetic fingerprint.
Organisers at the Barcode of Life Initiative (BOLI) say that the technology will aid researchers in a host of areas which rely on accurate identification of species of plants and animals, as well as other organisms. This includes identifying and protecting endangered species, sustaining natural resources including fish stocks, understanding marine biodiversity, carrying out basic research in taxonomy (identifying and labelling distinct species), controlling agricultural pests, stopping vectors of human disease such as mosquitoes and monitoring environmental quality.

While not exactly barcoding in the sense that Silver and Woodland imagined it, the initiative aims to use a relatively minute stretch of DNA (about 648 DNA "base-pairs" compared to the billions of such base pairs which make up many organisms) called a barcode sequence.

This barcode sequence will be tracked in a range of organisms. Subtle differences within this 648 letter code will give the researchers a unique label for every species. This particular barcode sequence, while excellent for use with most animal, butterfly, bird and fish groups isn't suitable for use with plants. The meeting in Mexico this week aims to propose a plant barcode sequence so that the work can continue.

With the information now available online, researchers are hoping that the job of identifying species has now become a whole lot easier.