Welcome to a new monthly series called CABI Author Focus. Each month one of the many talented authors or editors of books published by CABI will be writing about an element of their research. This month Kurt Lamour, editor of Phytophthora: A Global Perspective, writes for us on his experiences of this plant-damagng pathogen. As well as Phytophthora, Kurt co-edited Oomycete Genetics and Genomics: Diversity, Interactions and Research Tool with Sophien Kamoun.
Potato famine! Starvation and emigration! For many folks the only Phytophthora they’ll ever hear of, albeit tangentially, is through tales of the infamous potato blight that occurred in mid-1800 Ireland. I’ve often used the famine as a reference point to help answer questions concerning what it is I do for a living; although I’ve learned this conversational strategy can be tricky.
Nonetheless, even if the blight organism (P. infestans) is not the famine-producing monster I once thought it to be, Phytophthora species do in fact cause tragic and spectacular losses of life (plants!) and livelihoods. As I’ve studied the vegetable pathogen P. capsici over the past 15 years, I’ve witnessed firsthand the havoc wreaked once it has been introduced to farms in Michigan and Tennessee. I vividly recall a Michigan farm where I walked with three generations of farmers (grandfather, dad, and son) to inspect acre after acre of pickling-style cucumbers that looked like they’d all been dipped in powdered sugar. Needless to say, this sugar was not sweet and meant the fruit were severely infected and covered in spores. The farm had successfully produced cucumbers since the 1950’s and the grandfather and father looked at the son while asking me “How did this happen?” For these guys, large-scale disease and being forced to default on their contracts reflected poor stewardship – something that had never happened on their watch.
I felt bad for the son who’d only been in charge of the farm for a few years. As I’d done many times before and since, I explained how this epidemic was not any of their faults. It may never be clear how the disease made it to their farm, but, P. capsici can be exceptionally pernicious and is a serious problem on a wide variety of vegetables worldwide. In most cases, there are no effective chemical controls and even worse, the pathogen makes thick-walled dormant spores (oospores) that survive in the soil for years (like weed seeds). If even a few oospores germinate and cause infection, the disease can multiply and spread very rapidly – often just when a field is ready for harvest. I once counted and estimated the number of viable spores on the surface of a single squash at around 340 million. I’d often bring a picture of the squash with the caption “340M propagule timebomb” to show farmers (see picture). Each of these spores can release 20 to 40 swimming zoospores in rain or irrigation water and not surprisingly, it had rained heavily a few days prior to my visit this cucumber field. No doubt this rain event launched a deadly flotilla from what may have been a very limited amount of infected plant material - reducing their crop to a complete loss.
Phytophthora capsici is representative for species in the genus as a whole; species which attack a huge range of important plants in the wild and managed settings. There’s a fairly large group of scientists worldwide who’ve dedicated their careers to studying these enigmatic and often intractable organisms. Over the past year I’ve had the profound honor of guiding a group of “Phytophthora-ologists” through the process of collating our collective knowledge in the form of a book (Phytophthora: A Global Perspective). This was a highly rewarding venture and since I’m not capable of adequately summarizing the contributions of 60+ authors in this short space, I can only encourage anyone with an interest in Phytophthora to check it out.