Kiwifruit fungal pathogen workshop

A biosecurity incursion of a fungal pathogen such as Brazilian Wilt (Ceratocystis fimbriata), could severely impact our kiwifruit industry as it has to growers in Brazil where kiwifruit may no longer be an economically viable crop.

Kiwifruit has been identified as one of the most susceptible crops to this pathogen which is spreading around the world and a number of new epidemics have appeared in the last 10 years, including on Hawaii where it is wiping out their native ‘ōhi’a tree, a close relative to our pōhutakawa.

While KVH leads industry preparedness for biosecurity threats, Zespri provides a significant financial contribution to research initiatives and manages a biosecurity research portfolio on our behalf.

Last week, KVH held a science workshop to identify research priorities for our most significant fungal pathogens, to be undertaken within this biosecurity research portfolio. The workshop was attended by 25 representatives from KVH, Zespri, B3, Plant & Food Research, Landcare Research, Scion, NZ Avocados and the Ministry for Primary Industries.

Some of the key points from the day that will be of interest to growers include:

• Brazilian Wilt (Ceratocystis fimbriata) – the kiwifruit industry has already invested more than $200k into research to improve our preparedness for this pathogen, including pathogenicity screening of cultivars and the development of diagnostic tools, in addition to other work funded elsewhere. However, there are still many fundamental knowledge gaps, such as how long does it take from when a vine is infected to when symptoms are expressed? Could the pathogen already be in New Zealand but not yet expressing symptoms? Is kiwifruit susceptible to Ceratocystis strains in Hawaii as well as those in Brazil? And what about strains in Indonesia, Oman, China etc? From a long list of questions, the group workshopped a priority list that will be used to shape research projects for the next financial year.
  
  
• Verticillium Wilt – In Chile, certain kiwifruit cultivars seem susceptible to Verticillium Wilt. Several New Zealand scientists have visited the region to better understand the pathogen that causes this. The development of a diagnostic tool to firstly determine if it is already present in New Zealand (and if not, detect it should it arrive) was agreed as a research priority for this pathogen.
  
  
• Phytophthora – Rebecca Ganley, a Phytophthora expert from Scion, stated that Phytophthora around the world are evolving and we are constantly seeing new diseases from these pathogens. Just over 10 years ago there were no foliar Phytophthora on Radiata pine trees, now there are three, thought to have been a case of the pathogen evolving to infect new hosts.
  
  In New Zealand, Phytophthora typically affects only kiwifruit vines in poor growing environments or under stress, but observations from other industries suggest that new aggressive strains could affect vines even in good soil types. There are thought to be around 30 Phytophthora species in New Zealand, and several hundred offshore, potential many more that we don’t know of.

The group agreed that the workshop was an effective way of bringing the science community together to discuss research needs for the kiwifruit industry, and a similar approach will be taken for other groups of threats such as insects, viruses and bacteria.