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Influence of Specific Combining Ability and Sex of Gametes on Transmission of Ceratocystis ulmi Resistance in Ulmus. Alden M. Townsend, Nursery Crops Research Laboratory, Science and Education Administration, U.S. Department of Agriculture, Delaware, OH 43015; Phytopathology 69:643-645. Accepted for publication 5 January 1979. 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, 1979. DOI: 10.1094/Phyto-69-643.

When used as male or female parents, single selections of Ulmus glabra, U. carpinifolia, U. pumila, U. rubra, U. parvifolia, U. japonica, and a Netherland’s selection, N248 (U. wallichiana × U. carpinifolia) varied in ability to transmit moderate resistance to Dutch elm disease and rapid growth rate to their progeny. Symptoms among progenies varied more 4 and 12 wk after inoculation than after 56. Significant interaction (specific combining ability) occurred between parents in giving slight to moderate resistance to offspring. As male parents, U. carpinifolia 61 transmitted significantly more resistance than did U. glabra 72, when U. glabra 19 served as a female parent. With U. pumila 8 as the female parent, however, U. glabra 72 was a significantly better pollen parent than U. carpinifolia 61. Ulmus pumila 8 gave much more resistance as a female parent than as a male parent when crossed with U. glabra 72. Clones of U. pumila and U. parvifolia were about equally effective as male parents in increasing resistance to Dutch elm disease in progenies from several female parents.