Multiple Resistance in Induced Amphiploids of Zinnia elegans and Z. angustifolia to Three Major Pathogens. Veronica M. Terry-Lewandowski, Graduate Student, Department of Horticulture, University of Maryland, College Park 20742. Dennis P. Stimart, Assistant Professor, Department of Horticulture, University of Maryland, College Park 20742. Plant Dis. 67:1387-1389. Accepted for publication 7 July 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1387.

Inoculations with Erysiphe cichoracearum, Alternaria zinniae, and Xanthomonas campestris pv. zinniae were performed on colchicine-induced amphiploids of Zinnia elegans and Z. angustifolia to determine whether the newly derived germ plasm was resistant to three major pathogens of the popular garden ornamental Z. elegans. Experimental results demonstrated that the amphiploids possess high levels of resistance to E. cichoracearum (causal agent of powdery mildew) and A. zinniae (causal agent of Alternaria blight) and moderate to high levels of resistance to X. campestris pv. zinniae (causal agent of bacterial leaf and flower spot). These amphiploids will be valuable intermediaries in the transfer of multiple genes for disease resistance from Z. angustifolia to Z. elegans.