By Katie Pavid
Scientists believe that the arrival of just one more ash dieback spore could kill off Europe's remaining ash trees.
The dieback problem could have been caused by just one or two mushroom-like fruiting bodies of a fungal pathogen, according to a comprehensive genome sequence study published in Nature Ecology & Evolution.
Analysis suggests the spore came to Europe from Asia, where it grows on Asian ash trees without causing disease. But the pathogen has been devastating European varieties.
The study suggests that even the least susceptible ash trees could be at threat from the introduction of just one more spore from East Asia.
Dieback threatens 95% of all European ash trees and has already killed or severely damaged a quarter of the species in southern Sweden, and destroyed more than 80% of young ash trees in Norway.
A large team of scientists worked on the study, including senior author Matthew Clark, a research leader in plant interactions at the Museum.