Variability of host and pathogen in Hypoxylon canker of aspen

Abstract

Sapling-sized quaking aspen (Populits tremuloides) in five natural clones were inoculated with mass and single ascospore cultures of Hypoxylon mammatum. Fungus isolates varied in ability to produce cankers. 'Conidial-type' isolates generally produced few cankers, while 'mycelial-type' isolates produced cankers on 87.7% of inoculated branches. Isolates from a given ascus inoculated into a clone generally produced cankers of similar length after 2 months. However, some significant differences in canker length did occur. Clones varied in susceptibility to canker enlargement. No single isolate produced the largest cankers on all clones.