Virginia Tech, USA, and University of Tuscia, Italy
International research team to unravel origin of Psa
Since 2008, Pseudomonas syringae pv. actinidiae (Psa) has been threatening the world’s kiwifruit industry destroying orchards in Europe, South America and New Zealand putting the world kiwifruit industry in jeopardy. Psa causes a disease called “canker of kiwifruit”, which affects all parts of the kiwifruit plant, in particular, a red or white bacterial slime oozes out of stems and branches. In the worst case, the entire plant wilts and dies. In the four years since it was first reported in Italy, the bacterium has already caused hundreds of millions of dollars in economic losses. A similar disease broke out in the 1980s in China and Japan, but nobody knew if it was the same pathogen that is now wreaking havoc throughout the rest of the kiwifruit world.
The research led by Boris Vinatzer — associate professor in the Department of Plant Pathology, Physiology, and Weed Science in Virginia Tech’s College of Agriculture and Life Sciences and by Giorgio M. Balestra — senior researcher in the Department for Agriculture, Forestry, Nature and Energy, University of Tuscia, Viterbo, Italy, was published May 9 in the journal PLoS One and is the first study released in a scientific journal that traces the bacterium back to its likely origin of China.
“It was detective work,” said Vinatzer, “By sequencing the DNA, we were able to link all the bacteria back to a strain in China and determine where it probably all began.”
Vinatzer and Balestra were the lead authors of the paper. Angelo Mazzaglia of DAFNE, University of Tuscia in Italy and David Studholme of the University of Exeter in the United Kingdom were the first co-authors. Professor David Guttman, at the University of Toronto in Canada and Nalvo Almeida at the Federal University of Mato Grosso do Sul in Brazil also contributed their expertise to the team. Virginia Tech undergraduate student Tokia Goodman and graduate student Rongman Cai performed an important part of the experimental work and computer analysis in the Vinatzer laboratory.
Vinatzer and his team sequenced the entire DNA of Psa bacteria from kiwifruit trees in China, Italy, and Portugal. They also analyzed some bacteria from New Zealand, where kiwifruits are a nearly $1 billion industry. To find the root of the disease, the researchers examined how the bacteria may have evolved from the same ancestor by comparing the DNA from the different bacteria to each other. They found that the bacteria from China, Europe, and New Zealand were almost identical but one small difference in one region of the DNA linked the New Zealand outbreak to the Chinese bacteria. Vinatzer, Balestra, and colleagues think that the most likely scenario is that the bacterium was imported from China into Italy and from China into New Zealand independently.
“The first step in stopping the spread of aggressive bacteria like Psa is knowing where they come from and how they have spread,” Balestra said. “Now that we have sequenced the DNA and found its likely origin, we can start to figure out ways to stop it and similar bacteria from doing so much damage in the future.” When New Zealand reported the disease in 2010, the United State immediately banned all imports of kiwifruit plant material and pollen to keep it from infecting American crops and, so far, the bacteria have not been found in the U.S. However, if the disease were to break out in the USA, Vinatzer’s research will help slowing down its spread - or even eradicate the pathogen - through early and accurate diagnosis.
Besides having direct practical applications, the study will also lead to new insights into the adaptation of bacterial plant pathogens to crops and is as such an integral part of Vinatzer’s current research funded by the National Science Foundation and for research carried out by Balestra’s group on detection of bacterial pathogens, funded by the Italian Minister of Agriculture and Forestry Policy.
The full report can be found at on PLoS ONE: http://dx.plos.org/10.1371/journal.pone.0036518
More on Vinatzer’s research can be found here at http://www.ppws.vt.edu/~vinatzer/ and more on Balestra’s research can be found at http://www.agraria.unitus.it/interna.asp?idCat=244