Genetic Improvement of Elms and Other Tree Genera

Abstract

An extensive selection and breeding program for disease resistant, stress tolerant elm clones is being carried out. Efforts have involved making controlled hybridizations for improvement of not only resistance to aggressive and nonaggressive forms of Ceratocystis ulmi but also variable growth rate, leaf size, and form. The many new selections include several American elms as well as horticulturally desirable hybrid clones from European and Asiatic crosses. These selections are currently being evaluated in nurseries and cities across the U.S. Research with red maples has demonstrated opportunity to select from among seed source progenies for superior growth rate, winter hardiness, stem straightness, and tolerance to Verticillium wilt, ozone, and drought. Seed source studies are also being conducted with the Chinese elm {Ulmus parvifolia Jacq.), blue spruce {Picea pungens Engelm.), and European black alder (Alnus glutinosa (L.) Gaertn).