Wednesday, July 6, 2022

Living with Psa has become aim

Whether it’s regions dealing with a significant Psa-V outbreak or individual growers monitoring their property for signs of the disease; everyone wants answers.

APPROACH CHANGES: A Psa report says growers no longer ask how the disease arrived, but instead “how do we live with it”.

The questions no longer surround the ‘’how did it get here?” realm but have matured to “how do we live with this disease?”

The report “Status of Psa in New Zealand October 2012” was released to Kiwifruit Growers at their annual conference in Tauranga. It tells that tale of the $10 million that has been invested in Psa research. It shows the outcomes so far and the work still being undertaken; it is extensive and it is comprehensive.

Breeding Psa-tolerant cultivars is one of the main priorities. Plant and Food’s Psa Response Leader Stuart Kay notes that a breeding programme normally takes 10 years and this is trying to be condensed down to six.

“This year we have 100 different cultivars going into the initial clonal trials, the total number of plants that have gone into clonal trials in the entire history of the programme was, up until now, 30,” Kay said.

“We also have 60,000 plants going into field trials, this is up from 30,000. We used to molly coddle then through, now those that survive are the favoured child. The disease has turned the programme on its head.”

The recent news that Psa-V has been found in Hawke’s Bay has been somewhat of a shock to the industry. While it was expected, it was not expected this soon. The report emphasises how the research is being sped up, but Kay notes this has its dangers.

“If you can imagine you are only evaluating plants for two years instead of three to four, you are not as confident of the agronomic traits. You can get them into the market but as you shorten up your decision-making you increase your risk.”

The report makes it abundantly clear that the industry is in crisis mode and is throwing everything at this pathogen to understand and better work with it. The cover of the report proudly states that “more than 300 products have now been tested – in-vitro and/or in-vivo – for efficacy against Psa”.

Other areas of research include looking at different kiwifruit vine metabolisms, DNA sequencing, understanding the disease and product testing. All are vitally important in the fight against this disease. Much is still unknown and to a certain extent the industry is still finding out the very basics of the disease triangle – the interaction between the plant, the bacteria and the environment.

One step forward is the development of the Psa-V Risk Model. Noting that Psa-V is mostly spread by weather events there is now a model that forecasts the risk of Psa infection events based on the weather conditions. Growers can now plan the management processes on their orchard around the forecast risk of Psa-V infection.

No one is sure how long the industry has but this report shows it is working together to find a solution as quickly as possible.

Ian Warrington, former CEO of HortResearch, provided a telling foreword to the report. He notes “it will take time to develop the understanding (of this disease), to pull the pieces of the puzzle together and define the relative importance of each of them – but they are all being evaluated”.

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