Predicting the risks and impacts of Xylella fastidiosa using sentinel plant network

This three-year project was completed in mid-2022.

Project Abstract

We used the sentinel plant network to improve New Zealand’s preparedness for an incursion of the devastating bacterial plant pathogen Xylella fastidiosa. This pathogen can cause severe disease and mortality in hundreds of plant species, including many economically important species, especially grapevines and olives. In 2012 we confirmed that New Zealand native species growing in California, where they are exposed to the pathogen and its insect vector, are also susceptible to the pathogen. We wanted to develop methods to detect the pathogen to sequence-type level directly from plant material (without culturing), as would be desirable in an incursion response. We intended to collect fresh material from the infected New Zealand native plants in California, but our travel plans derailed when the COVID-19 pandemic broke. We then tried to activate the plant sentinel network to collect the samples for us and send them to New Zealand. By the end of the project we received samples from one garden. We learned that at least half of the plants we sampled in 2012 have either died or have been removed from the live collections because they have lost aesthetic value. We can only speculate that Xylella was the cause of death or loss of aesthetics. Significantly, while we could not perform a cultural ceremony prior to sampling the plants as intended if we had gone in person, MPI kaihautū performed a whakatau (ceremony) to welcome the repatriated samples and remove tapu. This opened the way for the research into diagnostic tools to continue.

Biosecurity outcome

• The risk to some NZ indigenous/native plant species (incl. taonga) from Xylella fastidiosa will be better understood (incl. hosts, impact, strains)
• Molecular diagnostics protocols will be tested to improve resolution beyond the pathogen species level
• Methods for sequencing Xylella at subspecies and sequence type levels from plant tissue will be validated

Science outcome

• The sentinel/expatriate concept for risk assessment will be tested using NZ indigenous/native plants found within the distribution of Xylella in California
• A greater understanding on host/pathogen relationships will be established by establishing the host list for Xylella (California strain) for some NZ plants

Key end users/stakeholders

Implementation:  Effectiveness of sentinel (expatriate) concept is reported directly to MPI (Science & Risk – Plants & Pathways, Diagnostics & Surveillance Directorates (PHEL and SII), and Intelligence Planning and Coordination Directorate (Biosecurity Intelligence Team)) and International Plant Sentinel Network (Botanic Gardens Conservation International).  Generic learning is shared with other sentinel projects (i.e. B17.4, B19.3).  Specific information on biosecurity risk from Xylella will be shared with the MPI, DOC and the GIA Xylella Working Group.

For more information and publications from this and other projects, visit Zotero.

Zotero can be found on the B3 homepage under ‘Outputs.