Response of Butternut Selections to Inoculation with Sirococcus clavigignenti-juglandacearum.

Butternut trees (Juglans cinerea) clonally propagated via grafting from source trees with putative resistance to butternut canker were inoculated monthly with two isolates of Sirococcus clavigignenti-juglandacearum in a field planting in Minnesota. Significant differences in resulting canker length were found among (i) month of inoculation, (ii) accession, and (iii) isolate. Results support the suggestion that canker-free butternut occasionally found growing among butternut severely affected by butternut canker potentially have disease resistance and may have value for genetic conservation and restoration of the species. Developing an effective resistance screening technique will require additional information on the natural infection process and testing under various climatic conditions across the range of butternut.