Colorful symptoms of Cytospora canker (Cytospora sp.) on the trunk of an aspen tree (Populus tremuloides).
Image by William Jacobi, Colorado State University.
from Bugwood.org used under a Creative Commons Attribution 3.0 License..

Cytospora canker (Cytospora sp.) -- spore tendrils emerging from the trunk of a tree.
Image by William Jacobi, Colorado State University.
from Bugwood.org used under a Creative Commons Attribution 3.0 License..

Cytospora chrysosperma (Pers.:Fr.) Fr. is a fungus that causes a tree disease called Cytospora canker. It attacks several hardwoods, notably trees used for bioenergy such as cottonwood, trembling aspen, and willows. The pathogen invades the stems, branches, and twigs of the host trees and forms cankers. The fungus spreads by producing conidia (asexual spores) within fruiting bodies (pycnidia) on the cankers. The spores ooze out, forming long, orange-red, coiled "spore tendrils". Perithecia of the sexual stage (Valsa) are rare and appear under the bark. This pathogen can cause serious damage in forest nurseries, young plantations, and in horticultural settings.

Attacks by pathogens represent one of the most important threats to the sustainable growth of bioenergy trees in plantations. Outbreak prevention depends largely on a better understanding of how pathogens infect trees so that resistance can be developed and on early detection, spread of the disease can be reduced through monitoring and surveillance. Since pathogens of poplars and pines tend to track their hosts worldwide better detection and surveillance are essential. This can be challenging since pathogens can remain dormant or have endophytic stages in the host tissues. The genome sequencing of Cytospora chrysosperma is part of a larger effort, the Pathobiome Database for Bioenergy Trees Project, that aims at sequencing the genomes of pathogens that share the same host trees in order to identify common and unique genomic signatures. By sequencing and comparing the genomes of the most important pathogens of poplars and pines, we plan to create a database that will be used to develop tools for the detection, monitoring, surveillance and rapid response of pathogens in these economically and ecologically important trees.