Differences in Conidial Morphology Among Isolates of Sphaeropsis sapinea. Wang Cheng- Guo, Visiting Scientist, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Robert A. Blanchette, Associate Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108; and William A Jackson, Technician, and Marguerita A. Palmer, Research Plant Pathologist, U.S. Department of Agriculture, North Central Forest Experiment Station, St. Paul, MN 55108. Plant Dis. 69:838-841. Accepted for publication 28 May 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1985. DOI: 10.1094/PD-69-838.

Thirty isolates of Sphaeropsis sapinea (=Diplodia pinea) from 10 countries were separated into two groups on the basis of conidial morphology. Scanning electron microscopy of mature spores demonstrated that type A isolates had smooth surfaces and type B isolates had pits distributed over the conidium surface. The separation of isolates into two groups may help to explain the variation in cultural characteristics and results of pathogenicity tests observed by researchers working with S. sapinea.