Response of Siberian Elm to Inoculations with Sphaeropsis ulmicola. J. M. Krupinsky, Plant Pathologist, USDA, Agriculture Research Service, Northern Great Plains Research Laboratory, P.O. Box 459, Mandan, ND 58554-0459. R. A. Cunningham, Research Geneticist, USDA, Agriculture Research Service, Northern Great Plains Research Laboratory, P.O. Box 459, Mandan, ND 58554-0459. Plant Dis. 77:678-681. Accepted for publication 3 March 1993. 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, 1993. DOI: 10.1094/PD-77-0678.

Eighty-one clones of Siberian elm (Ulmus pumila) were screened for resistance to Sphaeropsis ulmicola (= Botryodiplodia hypodermia) to determine if different levels of disease reaction or canker development could be detected. In 1989, inoculations with S. ulmicola resulted in significant differences among clones for branch dieback and canker length. In 1990, three clones with some resistance (small cankers) and three susceptible clones (large cankers) were inoculated with six isolates of S. ulmicola. On the basis of branch dieback and canker length, these clones were significantly different and responded similarly to inoculations performed in 1989. No significant differences in canker development among the six isolates were detected, and the isolate × clone interactions were not significant. These studies indicate that branch inoculations of clones with S. ulmicola will be useful in ranking or grouping clones based on their relative susceptibility. The putative resistant clones can be identified and utilized in an elm breeding program.

Keyword(s): windbreaks.