Physiological and molecular approaches for identification of Hypoxylon mammatum from Populus tremuloides tissue

Aspen clones grown in tissue-culture were subjected to dark treatment and inoculation with Hypoxylon mammatum ascospores. Aspen plantlets responded to dark treatment with changes in peroxidase activity. The plantlets did not respond significantly to inoculation with H. mammatum ascospores. The peroxidase activity response to dark treatment may have overshadowed the response to inoculation.; Unwounded aspen clones grown in growth-chambers were inoculated with ascospores of H. mammatum. Peroxidase activity of the clones increased, decreased, or remained the same in response to inoculation depending upon the clone and replication.; Peroxidase activity of uninoculated growth-chamber grown clones was related to salicin concentrations of the same clones grown in tissue culture determined by Kruger and to a phenology dendrogram produced by Moguel-Esponda using RAPD analysis. Salicin concentration was previously reported to be an indicator of resistance in aspen. RAPD analysis was previously reported to be capable of characterizing clonal affinities but not resistance.; An oligonucleotide primer for H. mammatum was developed by sequencing from the V-3 variable region of the large subunit ribosomal DNA. The primer was specific for H. mammatum when compared to other fungi isolated from aspen stems. The primer successfully identified H. mammatum from infected field-grown aspen branches. Identification of H. mammatum in aspen tissue will facilitate further investigations on theorized relationships among aspen, insects, the environment, and the fungus.