VIEW ARTICLE

Resistance

Evaluation for Bacterial Blight Resistance in Beans. M. Zapata, Assistant phytopathologist, Crop Protection Department, University of Puerto Rico, Mayaguez 00708; G. F. Freytag(2), and R. E. Wilkinson(3). (2)Research geneticist, Agricultural Research Service, U. S. Department of Agriculture, Tropical Agriculture Research Station, Mayaguez, PR 00708; and (3)Associate professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14850. Phytopathology 75:1032-1039. Accepted for publication 14 February 1985. 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, 1985. DOI: 10.1094/Phyto-75-1032.

Strains of Xanthomonas isolated from Phaseolus vulgaris, P. coccineus, Vigna unguiculata, and Glycine max were differentiated according to pathogenicity and serological relationships. Each strain was inoculated on primary leaves of young plants, trifoliolate leaves on plants in the flowering stage, and on detached trifoliolate leaves and pods. Several inoculation methods were compared. Inoculations at the vegetative stage of plant development were less reliable than those at the reproductive stage. X. campestris pv. phaseoli (X.c. pv. phaseoli and X.c. pv. vignicola, but not X.c. pv. phaseoli (from P. coccineus) and X.c. pv. phaseoli (var. fuscans) induced symptoms during the reproductive stage only. Inoculation of detached leaves did not produce reliable results. Of various inoculation methods, the needle-scratch on pods gave the quickest and most uniform results. In early tests, field selection 235-1 from an interspecific cross (P. vulgaris x P. coccineus) and several breeding lines from Cornell showed significantly higher resistance to all pathogen strains compared to susceptible local cultivars La Vega and W-117. Subsequent tests with X.c. pv. phaseoli (var. fuscans) and X.c. pv. phaseoli (from P. coccineus), chosen for virulence in a wide range of hosts, confirmed this high level of resistance. These highly resistant lines also showed field resistance in Puerto Rico.