14 July 2021

Dr Richard Winkworth, with one of the field-based assays in development.

Plant pathogens pose an ongoing risk to agriculture and the conservation estate in New Zealand. In the past decade the country has experienced devastating epidemics caused by Pseudomonas syringae pv. actinidiae (Psa) on kiwifruit and Phytophthora agathidicida on kauri.

In responding to these epidemics, research teams from Project 3 made significant contributions to:

  • Pathogen detection, including a field-based LAMP assay for P. agathidicida, and PCR-based assays for Psa. LAMP-based assays are a significant advance over plate-based baiting assays, as they are generally cheaper and more robust.
  • Epidemic origin, including the first paper postulating the timing of the origin of P. agathidicida in New Zealand, and a highly cited paper on evolution of Psa.
  • The molecular determinants of disease, making substantial progress in understanding how P. agathidicida and Psa cause disease.
  • Understanding the relationship between excision and Mobile Genetic Elements (MGEs), including Integrative and Conjugative Elements (ICEs). These are crucial entities in the evolution of prokaryotes, as they are the main source of laterally acquired genetic information. We made crucial advances in understanding the relationship between excision and transfer rate, resulting in several high-profile publications in internationally reviewed journals.

The P. agathidicida team particularly focused on engaging with Māori. We studied the expression of P. agathidicida genes in kauri tissue in partnership with Te Roroa and the Scion Healthy Trees Healthy Future programme. We developed the hybrid LAMP assay in partnership with Te Kawerau ā Maki and Te Roroa, and used it in partnership with iwi/hapu in Auckland, the Kaipara, and Northland, where it has been, or is being, used to inform decision-making.

One very important outcome of our research has been the high calibre of new researchers we have trained and supported. Drs Carl Mesarich and Jay Jayaraman now have permanent positions with Massey University and Plant & Food Research. The late Dr Pierre DuPont was employed by ESR. Several former students have also gone on to permanent research positions within New Zealand, ensuring bioprotection science is in good hands.