When it comes to fungi, we usually think of mushrooms or baker’s yeast. But while these are useful, there’s a sinister side to the fungal kingdom. Fungal pathogens can severely impact agriculture and forestry, and global trade risks introducing new pathogens into native ecosystems.
In a new PLOS Biology study, Benjamin Sikes, now at the University of Kansas, and colleagues used 133 years of data to investigate how New Zealand’s biosecurity program has affected the invasion and spread of fungal plant pathogens. I interviewed Sikes via email to find out more about how such policies might tackle the pathogen problem.
What drew you to study microbial ecology?
Most people love discovery, and microbes give me an easy avenue to do just that. Microbial ecology allows us to look inside the tiny universe surrounding us (and within us) to understand how it works and provides the functions on which we all depend. Some of those functions feel like superpowers. In my pre-microbe days, I remember being amazed to learn in a paper that fungi in roots of certain plants allow their hosts to grow in hot springs at 60 degrees Celsius!
Could you introduce us to the fungal kingdom? Do you have a “favorite” fungus?
Fungi are among the most ubiquitous organisms on earth and are found in all biomes and most microhabitats. Fungi have some unique attributes, like the thread-like bodies of most species, and are excellent subjects for studying broad biological principles related to cell biology, biochemistry, molecular genetics, ecology, evolution and symbiosis. I saw some amazing fungi when I visited New Zealand, but my current favorite fungus is the cinnabar polypore (Pycnoporus cinnabarinus), a bright orange shelf fungus that is used industrially to break down lignin (it is a white-rot decomposer) and for coloring.
Pycnoporus cinnabarinus, the cinnabar polypore fungus
Could you tell us about beneficial and pathogenic fungi?
Pathogenic fungi cause some of the greatest economic losses of crops worldwide, but most of these crops also depend on beneficial partnerships with fungi for their nutrition. For example, rust and smut fungi commonly infect many of our food crops and require crop rotations and chemical treatments to combat them. In contrast, more than 85 percent of all plants, including most crops and trees, form essential symbioses with mycorrhizal fungi through their roots, allowing the plant to gain greater access to soil nutrients and water.
In your study, you analyzed the introduction and spread of pathogenic plant fungi in New Zealand. Why are these fungal pathogens a biosecurity concern, and what is New Zealand currently doing to tackle them?
Pathogenic fungi can have huge impacts for economies like New Zealand’s that depend on primary industries such as agriculture and forestry. As trade and imports have increased, there are more opportunities for new pathogens to arrive, so effective biosecurity is critical to shield primary industries and the broader economy. New Zealand is a global leader in biosecurity and has an interest in evaluating pathogen arrivals and whether their biosecurity measures are effective.
What did you find out about the spread of fungal pathogens in New Zealand since records began?
Since the late 1800s, the rate of arrivals of new pathogens targeting New Zealand’s economically important plants has risen. The rate in the first half of the 20th century matched the exponential increase in trade volume, but around 1980 the annual rate began to slow, even as import trade volume and international travel to New Zealand continued to grow exponentially. This overall pattern is actually a product of different rates among sectors: new pathogens in agricultural crops started to slow from the mid-20th century following specific biosecurity measures, but pathogens in forestry and in fruit trees have continued to increase.
What most surprised or interested you about your findings?
A slowing rate of arrivals of new pathogens was welcoming, but surprising. Many recent papers have highlighted the global spread of fungal pathogens, so seeing a slowdown in New Zealand was unexpected. The timing of slowdowns for particular sectors appears to follow implementation of specific biosecurity measures, which gives us hope that we can change the trajectory of invasions if we can effectively target their entry pathways.
What do you hope your findings might lead to, and what are the next steps for your research?
These analyses are only made possible by the accumulation of more than a century’s worth of meticulous observation by individuals in the field. These give us the power to assess long-term trends that are critical to protect economies and evaluate policy effectiveness. Our continued work is using this database to map how native and nonnative plants and fungi interact, and whether those interactions might help predict susceptible areas for new pathogen spread.
Research Article: Sikes BA, Bufford JL, Hulme PE, Cooper JA, Johnston PR, Duncan RP (2018) Import volumes and biosecurity interventions shape the arrival rate of fungal pathogens. PLoS Biol 16(5): e2006025. https://doi.org/10.1371/journal.pbio.2006025
Images Credits: Scot Nelson, Flickr CC0; Benjamin Sikes; Patrick Harvey at Mushroom Observer, Wikimedia Commons CC-BY; Benjamin Sikes