Source: Radio New Zealand
Dr Falk Kalamorz and Rebecca Manners study a kiwivine plant within an outside level 1 containment area. Craig Robertson
Follow Our Changing World on Apple, Spotify, iHeartRadio or wherever you listen to your podcasts.
In 2010 the kiwifruit vine killing bacterial disease Psa-v was found in a Bay of Plenty orchard.
What followed was job, livelihood and monetary losses for many North Island kiwifruit growers as a variety of gold kiwifruit, Hort-16A, proved to be particularly susceptible to the disease.
Unfortunately, the disease spread to other kiwifruit growing regions in the North Island, including Northland, the Coromandel and the Waikato. But this aggressive version of the plant bacteria never made it to the South Island.
And so, a team of kiwifruit breeders and scientists devised a system to keep it that way.
North Island tissue culture
“The way we are doing it in New Zealand is more stringent than what we’re doing if we’re exporting material,” says the Bioeconomy Science Institute’s Dr Ed Morgan.
Based in Palmerston North, Ed leads a team of scientists responsible for doing a lot of plant tissue culture and moving plants around the world, and around New Zealand.
Following the Psa-v outbreak, the Bioeconomy Science Institute was approached by kiwifruit company Zespri about developing a plan to enable plants to safely move from the North to South Islands, without any risk of bringing the disease south.
This would allow South Island growers to purchase cultivars bred in the North Island and allow the Kiwifruit Breeding Centre (KBC – which is 50:50 Zespri and Bioeconomy Science Institute owned) to continue its work testing kiwifruit vines in different environments and different climates at its nursery in Motueka.
North Island cultivars to be moved are sprouted from budwood, and then four or five weeks later sent to the Palmerston North lab. From there, plant tissue cultures are established.
In this contained environment, the new plant tissue cultures go through several cycles of disease-checking in the lab, culminating in a PCR test by an external, independent lab which specifically looks for a piece of the Psa-v genome.
Only if they’ve been cleared through three or four checks, and the PCR test, will they be considered for sending south.
But that’s just the beginning.
Kiwivine plants are checked carefully for any signs of disease. Craig Robertson
South Island post entry quarantine
After they cross the Cook Strait, the tiny tissue culture plantlets, just 2-5 centimetres in size, with a few leaves and their first roots, will arrive in the Bioeconomy Science Institute in Lincoln, just Southwest of Christchurch.
Here they spend six months in a glasshouse where they are checked weekly for the tiny brown dots with yellow halos that are the tell-tale sign of Psa infection.
After that they are tested again by PCR. If they clear that stage, they then spend a further eight months across a new spring and summer growing season in pots in an enclosed outside area, again with weekly checks and a final PCR test.
Even then, there is one last step to go. If the plants are cleared, they will spend another year either at the onsite farm in Lincoln or in a nursery site outside of the South Island growing regions as an extra precaution.
While Zespri and the KBC are the customers, and the Bioeconomy Science Institute is providing this scientific service, it’s Kiwivine Health (KVH) who is the overseer of this pathway.
KVH was established in 2010 when the Psa outbreak occurred, with the mandate of managing the spread and impact to kiwifruit growers within the industry. The movement of kiwifruit plants falls under their pathway plan, a regulatory plan under the Biosecurity Act, and each year they audit the steps in the pathway.
Falk and Rebecca check the newly arrived kiwivine plants in the contained glasshouse. RNZ / Claire Concannon
While today growers use kiwifruit vine varieties that are less susceptible to Psa-v, it still has an impact on plants every year says KVH chief executive Leanne Stewart. “There needs to be active prevention programs in place every season, to make sure that it doesn’t become an issue and infections don’t run rampant on orchards.”
Currently the pathway can accommodate about 120 plants each year and so far they’ve not had any sign of Psa-v in any of the plants that have arrived in Lincoln. And Leanne is keen to keep it that way.
“In the South Island, we grow Heyward and Sun Gold and Ruby Red kiwifruit. If it was to get into the South Island, those varieties are susceptible to Psa. Not the same as Hort-16A, but there still needs to be active management of the bacteria. Because it’s a colder environment down there we could see a high level of infection, which we want to avoid.”
Sign up to the Our Changing World monthly newsletter for episode backstories, science analysis and more.
– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand