Role of Nonhost Species as Alternate Inoculum Sources of Xanthomonas phaseoli. C. R. Cafati, Rockefeller Graduate Fellow, Department of Botany and Plant Pathology, U.S. Department of Agriculture, Michigan State University, East Lansing 48824. A. W. Saettler, Research Plant Pathologist, Edible Legumes, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Michigan State University, East Lansing 48824. Plant Dis. 64:194-196. Accepted for publication 10 October 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, 1980. DOI: 10.1094/PD-64-194.

Rifampin-resistant mutants R15-1 of Xanthomonas phaseoli (Xp, cause of bean common bacterial blight) and R17 of X. phaseoli var. fuscans (Xpf, cause of bean fuscous bacterial blight) were used in studies on the role of weeds and other nonhost species in Xp and Xpf epidemiology. Xp grew epiphytically on leaves of various nonhost crop and weed species, and viable populations were recovered up to 21 days after bacteria were placed on leaf surfaces. Reciprocal secondary spread between susceptible bean and lambsquarters (Chenopodium album) and pigweed (Amaranthus retroflexus) occurred within 12 days after inoculation.