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How will pathogen communities change as climate warms?

Manaaki Whenua researchers, in collaboration with Dr Ian Dickie at the University of Canterbury, are using next-generation sequencing to try and understand what drives kānuka health.

Dr Kate Orwin, a senior researcher with Manaaki Whenua’s Land Use and Ecosystems team, says how a plant interacts with its neighbours, the soil underneath it, and the landscape that it is in can all influence plant health and how a plant resists pathogens.

The work is funded by the Bioprotection Aotearoa Centre of Research Excellence and has developed from an earlier project using molecular-based methods to quantify biodiversity across different land uses. As part of that project, researchers examined how land use influences which plant pathogen communities are found where.

“We are able to use the methods developed by former Bioprotection student Andreas Makiola in his PhD research on drivers of plant pathogen composition and richness, and take a similar approach to a different question,” says Kate.

Andreas’s research showed that in the face of future climate and land use changes, changes in plant pathogen community composition and richness at a plot-scale are likely to be driven primarily through changes in plant communities, rather than the direct effects of climate or soils. 

“What we are really trying to understand in this new project, is what drives health at an individual plant level, using kānuka as a model species,” says Kate. “In a broader sense, as the climate changes we potentially face more and different diseases, so understanding how to make systems more robust would be helpful.”

The first step is to study the characteristics of individual kānuka plants that have pathogens on their leaves or roots but no signs of disease. Using Banks Peninsula as an initial research area, postdoctoral researcher Dr John Ramana will be collecting samples from kānuka trees and stands across 30 sites with different rainfall, temperature, and soil properties.

Researchers will then test whether a core microbiome is shared among healthy plants, or if that microbiome is determined by environmental conditions. “It’s about taking a holistic approach and looking at a community of pathogens, rather than just a specific pathogen or the disease it causes,” says Kate.

“We are hoping to understand what makes a plant healthy – what is on its leaves, what is in the soil, what makes it able to resist disease? We want to test the hypothesis that healthy plants are not defined by the absence of pathogens, but rather by the absence of disease.”

Kānuka is ideal for this research as it is ecologically and culturally important, and grows in a range of habitats that should result in individual plants interacting with different microbes, soils, and neighbouring communities. 

The ultimate aim of the research will be to provide managers with guidance on how to manage their landscapes, for instance how to increase the health of kānuka plants to make them more resistant to disease in the face of climate change.

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