WELLINGTON, Feb. 28 (Xinhua) -- New Zealand scientists Thursday claimed they have genetic evidence that the Psa canker disease that has devastated the country's kiwifruit crops over the last three years originated in China.
The University of Otago biochemists said the strains of Psa ( Pseudomonas syringae pv. actinidiae) responsible for outbreaks in Italy in 2008 and Chile in 2010 also came directly from China.
The team used advanced genomics technology to sequence and compare the genomes of Psa strains from Japan, Chile, China, Italy and New Zealand to analyze the geographic origins.
The core genomes of the Chinese, Chilean, Italian and New Zealand strains were almost identical and likely shared a common ancestor around 10 to 15 years ago, Associate Professor Russell Poulter said in a statement.
"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," said Poulter.
The researchers were now sequencing another 20 strains, mostly from China, but also Korean and Turkish strains, focusing on an element of the bacteria that could move between cells of different strains and alter properties such as their infectiousness and resistance to antibiotics.
"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," said Poulter.
The results would help clarify the path by which Psa entered New Zealand, he said.
New Zealand Kiwifruit Growers president Neil Trebilco told the New Zealand Herald newspaper that the research highlighted the importance of border security.
"What we don't want, of course, is for another variant of Psa in New Zealand. Having the one we've got is bad enough, but having another variant would compound the problems for us."
At the end of November last year, 68 percent of New Zealand kiwifruit orchards were known to have the vine-killing Psa bacterium, up from 26 percent a year earlier.