How a pathogen outsmarted the potato

An intense game of genetic chess is taking place beneath our very eyes, in the soil where our beloved potato crops grow. This evolutionary battle between the humble potato plant and its mortal foe, Phytophthora infestans – the pathogen responsible for the devastating Irish potato famine in the 1840s – has puzzled scientists for years.

Now, research conducted at North Carolina State University is shedding new light on this “arms race” with an innovative study using fragments of historic potato leaves to examine both the plant’s resistance genes and the attacking pathogen’s effector genes simultaneously.

Breaking down walls: A revolutionary approach

The experts utilized small, 80 base-pair chunks of DNA, akin to magnets, to isolate similar pieces within the complex “soup” of DNA found on historic leaf samples.

Previously, researchers would focus on either the host (the potato) or the pathogen, but this dual enrichment strategy has opened a new front in understanding this host-pathogen relationship.

“It’s a first for looking at both potato and pathogen changes at the same time,” noted Jean Ristaino, William Neal Reynolds Distinguished Professor of Plant Pathology at North Carolina State University.

This radical method of investigation has only become possible recently, as the necessary genomics weren’t sequenced until around 15 years ago.

Pathogen evades potato defenses

Findings from the study indicate that the pathogen, Phytophthora infestans, is surprisingly skillful at dodging the potato’s defenses against late blight disease.

For instance, the FAM-1 strain of the pathogen was capable of overcoming the plant’s R1 resistance gene before it was even introduced into potato strains by plant breeders.

Such discovery suggests that the pathogen could have resisted the R1 gene even if it had been deployed much earlier, potentially owing to exposure to the wild potato variant harboring that resistance gene.

Battlefield for pathogens and potatoes

The study sheds light on how the pathogen’s effector genes have largely remained steady over time, with selective mutations enhancing its infectious capabilty.

This was particularly noticeable post-1937, when structured potato breeding programs began in the United States and elsewhere, in an effort to boost disease resistance.

Additionally, the researchers found that the pathogen managed to add a set of chromosomes to its arsenal between 1845 and 1954, the period during which the plant samples for the study were collected.

The promise of future studies

This research is immensely valuable, as it provides breeders with critical information about how the pathogen has transformed over time.

This knowledge could potentially be utilized to implement more stable resistance genes or to combine multiple resistance genes from different wild hosts.

“We now know what effectors have changed over time,” Ristaino stated. “Breeders may be able to use resistance genes that are more stable or pyramid multiple resistance genes from different wild hosts.”

And so, the game of genetic chess continues with new strategies and renewed hope of winning the game against the pathogen.

The importance of potatoes

Potatoes are not just a beloved comfort food; they are a vital staple crop that nourishes millions around the world.

Originating from the Andean region of South America, potatoes have transcended borders and cultures, becoming an essential part of diets in various countries.

Their versatility allows them to be prepared in countless ways, from mashed potatoes to fries, making them a culinary favorite across the globe.

Moreover, potatoes are packed with nutrients, including vitamins C and B6, potassium, and dietary fiber, making them a healthy choice for many.

As the global population continues to grow, ensuring the resilience of potato crops against diseases like late blight is crucial for food security.

The NC State research not only aids in understanding the complex interactions between potatoes and their pathogens but also plays a vital role in developing sustainable agricultural practices.

By improving potato resilience, we can help secure a reliable food source for future generations and support the livelihoods of millions of farmers who depend on this crop.

The study is published in the journal Nature Communications.

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