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Understanding the spread of plant diseases to tackle some of Aotearoa's major ecological threats - Annual Report 2023
13 April, 2024
Ayelen Tayagui in her University of Canterbury lab
Throughout human history, we have grappled with the challenges of devastating diseases. However, often overlooked is the impact of plant epidemics in influencing food security, migration patterns, and even socio-political landscapes. Phytophthora, meaning "plant destroyer" is a genus of oomyetes, fungus-like microorganisms that can cause significant disease in many plant species. Today, there are 30 species of Phytophthora known to be present in New Zealand with significant impacts on agriculture, forests and natural ecosystems.
Dr Ayelen Tayagui is a MacDiarmid Institute postdoctoral research fellow based at Te Whare Wānanga o Waitaha University of Canterbury. Working with Professors Volker Nock and Geoff Willmott, and Associate Professor Jenny Malmström from the MacDiarmid Institute and Associate Professor Ashley Garrill from Te Whare Wānanga o Waitaha University of Canterbury, Ayelen is working to understand the biology and the mechanisms used by Phytophthora species to infect their host plants and how these mechanisms adapt in response to environmental stress.
This could shed light on why certain plant diseases are so challenging to tackle.
Dr Ayelen Tayagui MacDiarmid Institute postdoctoral research fellow
"Phytophthora species have caused significant upheaval throughout history and continue to do so today. It was responsible for the blight that ravaged potato crops and contributed to the Irish Famine in the 1800s," says Ayelen.
Tackling the causes of kauri dieback
"Currently in New Zealand, Phytophthora agathidicida is receiving widespread media coverage for causing kauri dieback disease in kauri trees. Given that kauri trees are ancient and significant to the natural landscape of Aotearoa, their health is crucial for the country's native forests.
"Other prominent species include Phytophthora cinnamomi, known as the "biological bulldozer", which has the potential to affect 5,000 different plant species including avocado, chestnut, oak, peach, and pineapple."
Phytophthora have several means of spreading between plants including producing zoospores, reproductive cells that can swim independently using a flagellum to find a host.
Ayelen says the zoospores swim towards plant roots.
"Once within proximity of the new plant host, they shed their flagellum and form a thick-walled cyst, an encysted zoospore, that is ready to infect."
Advanced materials analysis
Ayelen and her colleagues are investigating how encysted zoospores manage their internal pressure, a process known as turgor regulation, while undergoing environmental stress. They are measuring the biomechanical and biophysical properties of zoospores, possible largely though advanced materials analysis methods developed through the MacDiarmid Institute.
"Zoospores are extremely small," she says, "only 10-12 micrometres in diameter, therefore it is difficult to penetrate the cell wall directly. Instead, we are using a technique called microaspiration to expose the zoospore to varying concentrations of different solutions to measure how the cell membrane deforms.
"Our findings indicate that zoospores of Achlya bisexualis, a type of oomycete, regulate their internal hydrostatic pressure in response to environmental stress."
The team's important discovery was featured on the front cover of the April 2022 volume of the international journal Fungal Genetics and Biology.
"There's now evidence suggesting different species of Phytophthora, some which cause significant disease in New Zealand plants, have this ability too. This could shed light on why certain plant diseases are so challenging to tackle."
By continuing this research, Ayelen and her colleagues hope that it will provide insight into developing environmentally sustainable strategies to combat the spread of diseases caused by Phytophthora species, a goal that becomes increasingly pivotal as the spread of plant diseases is exacerbated by climate change.
"But as with any research you are not guaranteed any particular outcome. In the lab you never know how an experiment will perform so you must have patience."
Raised in Argentina as the youngest of four by a hardworking single mother, Ayelen credits the circumstances of her upbringing as the primary source of her resilience.
They lived modestly, sharing a single room among nine family members until a move southward when Ayelen was nine enabled her mother to train as a teacher. Their circumstances improved from there.
"That was the first time I experienced what it was like to have running water and a toilet in my house. Sometimes I can't believe the things my mom was able to do. I always thought if she can do all that, why couldn't I achieve something that was a fraction of that?"
Ayelen's interest in science blossomed in high school and led her to study genetics. After completing her degree and gaining lab experience, she embraced the challenge of moving to an English-speaking country and moved to Aotearoa New Zealand in 2011.
Despite the language barrier, she persevered and eventually pursued her PhD in Professor Garrill's lab, where she still works today. Ayelen describes some of the challenges she faced as an early career researcher in New Zealand.
"The initial stages of my PhD were challenging as I had to also work to support myself prior to obtaining scholarship funding. Also adapting to a new culture while still learning English, not just spoken but also written, scientific English," says Ayelen.
"Now as a more established researcher, finding funding in New Zealand is always a challenge and it can be so frustrating to see many great ideas and projects going unfunded.
"It is tough, but at the end of the day, if you're lucky enough to do something you really love, I feel you are always successful. I am proud of where I came from and where I am today."
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