Study identifies bacteria that trigger frost damage to vines
[ The University of Melbourne Voice Vol. 2, No. 4
17 March - 14 April 2008 ] By Nerissa Hannink
A bacterial strain known overseas to trigger costly frost damage to grape vines has been identified in Australia for the first time by University of Melbourne scientists.
The discovery has been made by researchers at VitUM, the University’s Viticultural Research Group, in work at Dookie Campus.
Frost damage causes crop losses averaging more than $33 million a year in Victoria and South Australia.
The VitUM research team’s study has identified the ice nucleating strain of the bacterium Pseudomonas syringae – found on vines in the US and Europe.
VitUM scientists Dr Tom Hill and Ms Sonja Needs report the bacteria trigger the freezing of dew on leaves at much higher temperatures than occur on bacteria-free leaves, rapidly killing the entire plant shoot.
Their study adds to recent overseas reports that the same bact-eria are found in snowfall and hail around the world, where they may initiate ice crystals – essential for both snow and rain in temperate climates.
Dr Hill says existing frost counter-measures raise the temperature around the plants, which is expensive, inefficient and afforded by few, but a novel strategy would be to lower the temperature at which the plants freeze. This may be possible by inact- ivating the ice-nucleating bacteria. Without the bacteria the leaves do not freeze until below minus 50C).
The strategy could be to kill the ice-nucleating bacteria and displace them with ‘friendly’ naturally- occurring strains of the same species that do not carry the ice genes, or alternatively to inhibit production of the ice protein in the bacteria.
The research team is currently using DNA-based tools to develop novel anti-frost treatments that work in the vineyard.
Dr Hill describes the bacteria as microscopic predators living on the leaf and generating ice crystals which spread, penetrating like spears. “This destroys the cell structure enabling the bacteria to engulf the leaf. Next morning, when it thaws, they feast, killing the entire shoot,” he says.
“They are true Jekyll and Hyde bacteria. Their good side may be making rain, acting as organic cloud seeding particles. But their bad side is brutal: they may be responsible for causing millions of dollars of frost damage not only to vines but other horticultural crops as well.”
|
|
