Scientific evidence that the vine disease Psa-V originated in China may not be enough for growers to take a court case against the Ministry for Primary Industries.

New Zealand Kiwifruit Growers Inc. president Neil Trebilco says the research just released by the University of Otago is not enough to back a court case over a possible bio-security breach.

File photo.

'This is another important piece of evidence in understanding the disease but the report doesn't identify the vector,” he says.

NZKGI will re-evaluate, in light of the evidence, the possibility of taking the ministry to court, but Neil says it would be necessary to show how the disease arrived in New Zealand and that there was a failure of duty of care.

However, the work done by the University of Otago team in sequencing the genome of Psa-V was a vital piece of work in furthering the understanding of the disease.

'I want to thank the university of Otago team involved in the work and the post-harvest companies which helped finance it. This has provided yet another step in the long war against Psa.”

Neil says what is disturbing is the evidence that the bacteria has the ability to change its virility and mode of action and it is vital that no other altered strain of the disease enters the country.

Minister of Primary Industries Nathan Guy says it is not unexpected that Psa has potentially come from China.

What various studies, including this one, have shown is that it is inconclusive as to exactly how Psa entered New Zealand.

'The Ministry for Primary Industries are continuing to keep a watching brief on the issue of the pathway tracing and will follow up on any new information provided.

'The focus of the Government now is to support the kiwifruit industry the best we can. That is why in 2010 the Government provided $25million, matched by industry, to support the initial response and ongoing research and development.

'We are also working with Kiwifruit Vine Health to effectively implement the National Pest Management Plan.

'Government spending on biosecurity is now almost double what it was in 2000, and last year saw one of MPI's biggest border staff recruitment intakes ever.

'Following the Psa outbreak, MPI commissioned an independent review of import requirements and border processes for kiwifruit plant material. All recommendations from the Sapere report will be adopted, but at the same time the review found that any shortcomings at the border were not necessarily the reason Psa got into New Zealand.”

The Otago University study which shows Psa-V originated in China is published in the international science journal PloS One, and backs findings the university team made in May last year, when it linked the New Zealand Psa outbreak in 2010 to bacteria found in China, but said more data was needed to confirm the link.

Associate Professor Russell Poulter, Professor Iain Lamont and Dr Margi Butler, all from the University of Otago's Department of Biochemistry, have been working with the kiwifruit industry since the Psa (Pseudomonas syringae pv. actinidiae) bacterium was first detected in a Te Puke orchard in November 2010.

The arrival of new advanced genomics technology – through the government funded initiative, New Zealand Genomics Limited – allowed the Otago biochemists to show the New Zealand strain was significantly different from the Italian strain and, therefore, Italy could not have been the source.

Critically, it also put to bed any rumours that New Zealand may have been the source of historical Italian outbreaks.

The university says that through a process of elimination, Chinese pollen appears to be the likely source of New Zealand's outbreak.

The Otago biochemists have been able to source some Chinese Psa samples for sequencing and the results indicate that China is the original source of both the Italian and New Zealand outbreaks.

More recently, Psa has been confirmed in Chile and work has begun on sequencing these strains. Preliminary data suggests that the Chilean strain also originates from China.

"These findings paint a clear picture of an independent Chinese origin for both the Italian and the New Zealand outbreaks and suggest the Chilean strains also come from China," says Russell.

The researchers are now sequencing a further 20 strains, mostly from China but also Korean and Turkish strains.

"Some Psa may be inherently more virulent due to the particular ICE they carry. This has worrying implications as strains of kiwifruit that are resistant to one type of Psa might not be resistant to another," Dr Poulter said.

"This means strict border control by kiwifruit-producing countries is more important than ever."