A fungus called Mycosphaerella populorum has been infecting poplar trees across North America. Exactly how the fungus is so effective at infecting trees so rapidly and causing extensive damage has puzzled scientists.
The resultant disease of polar trees is called septoria leaf spot. The fungus causes foliar lesions and the lesions appear as small, circular to angular, white, grayish, tan, brown, or purplish spots with a dark border.
By using advanced genetic sequencing microbiologists have found out that the fungus uses extra genes to produce a toxin that leads to fatal lesions on the leaves, stems and branches of poplar trees.
It is speculated that the fungus has developed additional genes through gene transfer, gaining an enhanced toxic ability of time through interaction with other microbes. The fungus was first detected 10 years ago in eastern North America. Since then it has spread rapidly among poplar trees. The most recent area to be affected is in British Columbia, where numbers of black cottonwoods have been infected.
It is hoped that this new discovery will allow scientists to develop more effective methods for detecting the fungus, so that infected trees can be isolated and treated. The discovery may also lead to new treatment methods for trees that are infected.
The research was performed at the University of British Columbia. The results have been reported to the journal Proceedings of the National Academy of Sciences, in a paper headed “Horizontal gene transfer and gene dosage drives adaptation to wood colonization in a tree pathogen.”
In related news, with a different tree associated fungus, scientists have located the environmental source of fungal infections that have been sickening HIV patients in Southern California. The discovery was based on the science project of a 13-year-old girl, who spent a recent summer vacation gathering soil and tree samples.
