Psa bacteria tracked to China

06:44, Feb 28 2013

New research confirming the Psa bacterium which caused havoc in the kiwifruit industry originated in China also raises fears that genes transferring between Psa bacteria could make some strains even more infectious.

Contrary to a statement by New Zealand First leader Winston Peters yesterday - ahead of today's release of the Otago University research - the research does not identify how the Psa got into this country.

An industry representative is doubtful the work provides enough new information to enable the industry to take legal action against the Ministry for Primary Industries.

The new research by Associate Professor Russell Poulter, Professor Iain Lamont and Dr Margi Butler from Otago's biochemistry department was published in the journal Plos One.

The team completely sequenced and compared the genomes of Psa strains from Japan, Chile, China, Italy and New Zealand.

The team found that the core genomes of the Chinese, Chilean, Italian and New Zealand strains were almost identical and likely shared a common ancestor in China around 10-15 years ago.

Research under way now sequencing a further 20 strains, mostly from China, is focusing on a type of mobile element called ICE - integrative conjugative elements. Those elements can transfer between cells of different bacteria strains and alter properties such as their infectiousness and resistance to antibiotics.

“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. This means strict border control by kiwifruit producing countries is more important than ever,” Dr Poulter said.

Dr Butler said the research had not looked into the issue of how the Psa came into New Zealand.

"We don't have any discussion in our paper about the mechanism, or the avenue that it came into the country," she said.

For now, she did not expect any strong leads for fighting Psa would come out of the research. More time was needed to look at what was in the genome.

"Having a whole genome sequence will make life a little bit more straightforward for people who are trying to find chinks in the armour."

The Psa  bacterium was first confirmed in a Te Puke orchard in November 2010.

NZ Kiwifruit Growers president Neil Trebilco said his personal view was that the new research did not provide enough new information for a court case over a possible biosecurity breach.

Identifying how Psa got into this country was one of the clear links he expected would be needed before legal action could be taken against the MPI.

"This still is a live issue for us as an organisation. We haven't ruled out taking legal action and we still may. It depends on whether enough evidence turns up."

Many growers suspected the Psa had come into the country with imports of kiwifruit pollen or parts of kiwifruit flowers called anthers.


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