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PSA bacteria tracked to China, scientists say

Published: 12:33PM Thursday February 28, 2013 Source: Fairfax

Recent outbreaks of the virulent kiwifruit vine disease Psa originated in China, University of Otago scientists have confirmed.

As of last month, Psa-V had affected 69% of New Zealand kiwifruit orchards, cutting fruit yields and causing retail prices to rise by up to 20%.

Export volumes were expected to fall 10-13 million trays this season, with the most common variety of gold kiwifruit, Hort 16A, highly vulnerable to the bacterial disease.

Scientists said they have mapped the genome of the bacteria responsible for Psa, with final results published today in the journal PLOS ONE.

They analysed strains from China, Japan, Italy, New Zealand and Chile, finding evidence that recent outbreaks originated from China.

They also found distinct genetic encoding traits that may make the disease more aggressive.

These appear to have been transferred from bacterial strains attacking unrelated plants on at least three separate occasions, and may have triggered the virulent outbreaks.

Dr Matt Templeton, host-microbe interactions team leader in the Bioprotection Technologies Group of Plant & Food Research, said the paper indicated China was a likely source of Psa infection.

This had implications for managing the disease and in particular breeding for resistance.

"It also has important implications for our approach to both biosecurity and management, because we need to be sure we're looking out for the right things when protecting our borders and that we're taking the right steps to mitigate impacts post-border.

"The main conclusion of this paper would be strengthened by the analysis of more isolates from China."