VIEW ARTICLE

Response of Backcross Hybrids and Three-Species Combinations of Ulmus pumila, U. japonica, and U. rubra to Inoculation with Ceratocystis ulmi. D. T. Lester, Associate Professor of Forestry, University of Wisconsin, Madison 53706; E. B. Smalley, Professor of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 62:845-848. Accepted for publication 15 February 1972. DOI: 10.1094/Phyto-62-845.

Thirty-two elm progenies, including half-sibs and full-sibs from parental, F₂, and backcrosses were tested for response to artificial inoculation with Ceratocystis ulmi. Time of inoculation and species combination were the main sources of variation. Crosses among Ulmus pumila and a putative natural hybrid of U. pumila × japonica had low disease susceptibility. The introduction of germ plasm from U. rubra markedly increased disease susceptibility.