Using DNA markers as a tracking mechanism, a Simon Fraser
University researcher has discovered that British Columbia's escalating
blight problem - unique in Canada because it affects both potatoes and tomatoes
- most likely originated with the importation of diseased tomatoes from
Dr. Zamir Punja, director of SFU's centre for pest management,
says he was surprised at the results of his DNA study which also highlights
the importance of home gardeners routinely getting rid of diseased tomato
Caused by fungus, blight appears as large, brown blotches
on leaves, stems and fruit causing them eventually to shrivel and die. It
spreads through the release of spores.
"Tomato plants with blight result in high spore
levels and spores can travel up to 20 kilometres to infect both potato and
tomato plants," he explains.
Punja, who has been studying blight for five years,
urges home gardeners to get rid of infected tomato and potato plants by
burying or bagging them.
"Home garden tomatoes are rarely treated for blight
and diseased plants are usually left unattended throughout the summer which
leads to high spore levels. Disposing of infected plants will help the potato
industry and other home gardeners as well," says Punja.
B.C.'s growing blight problem has developed in part
because of increasingly wet summers, as well as new aggressive strains of
the fungus, according to Punja. "Diseased tomatoes are important, as
shown by our study of the DNA markers, because they produce genetically
complex strains of blight through sexual recombination," he adds.
There are no blight-resistant tomato varieties, although
greenhouse tomatoes are unaffected because they are enclosed.
Punja says blight has become an increasingly costly
agricultural disease in
Contact: Ken Mennell
Simon Fraser University