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Susceptibility of Intra- and Inter-Specific Hybrid Poplars to Agrobacterium tumefaciens Strain C58. Don E. Riemenschneider, Research plant geneticist, U.S. Department of Agriculture Forest Service, North Central Forest Experiment Station, Forestry Sciences Laboratory, 5985 Highway K, Rhinelander, WI 54501; Phytopathology 80:1099-1102. Accepted for publication 11 April 1990. 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, 1990. DOI: 10.1094/Phyto-80-1099.

Susceptibility of seedlings from 95 intra- and inter-specific hybrid Populus families and 27 F2 families of Populus deltoides to Agrobacterium tumefaciens strain C58 was evaluated. Controlled crosses were made between P. deltoides (females) and P. maximowiczii, P. balsamifera, P. nigra, and P. deltoides (males). At least one family from each parental species combination formed crown galls after inoculation with strain C58. Control plants, inoculated with sterile bacterial medium only, did not form galls. Gall tissue proliferated new gall tissue in vitro in the absence of phytohormones and produced nopaline. A second experiment, using 112 seedlings from six families, indicated that familial differences in susceptibility to crown gall were attributable to the female parent. Results demonstrated that, although A. tumefaciens strain C58 infected 27 of 95 hybrid poplar families derived from several parent species, susceptibility within one subpopulation could be attenuated by maternally inherited host genotype. Thus, although strain C58 may be used as the basis of vector construction for the transformation of many poplars, testing of individual hybrids and use of alternative bacterial strains may be necessary. Hybrid families of contrasting susceptibility may be useful in the study of the biochemical control of Agrobacterium virulence genes by tree species.

Additional keywords: breeding, crown gall, host range, in vitro, nopaline.