VIEW ARTICLE

Dutch Elm Disease in Clones from White Elms Resistant and Susceptible to Ceratocystis ulmi. W. A. Sinclair, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; W. D. Brener, former Experimentalist, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; Present address of junior author: Wisconsin Department of Agriculture, Plant Industry Division, Madison 53705. Phytopathology 64:675-679. Accepted for publication 26 November 1973. DOI: 10.1094/Phyto-64-675.

Ramets of Ulmus americana and U. laevis 4 mo to 2 yr old, from ortets resistant and susceptible to Ceratocystis ulmi, were inoculated with cell suspensions of C. ulmi in greenhouse tests. Ramets from resistant ortets showed less severe foliar symptoms and less extensive internal spread of C. ulmi than those from susceptible ortets when inoculated in mainstems after the annual period of maximum susceptibility or if inoculum was placed in xylem of current-season shoots. When mainstems of ramets were inoculated 4-5 wk after budbreak, no clones displayed resistance.