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Bacterial Blight of Beans Caused by Two Xanthomonas Pathogenic Types from Puerto Rico. Nader G. Vakili and Walter J. Kaiser, Plant Pathologists, Federal Experiment Station, Agricultural Research Service, U. S. Department of Agriculture, Mayaguez, Puerto Rico 00708; J. Enrique Pérez, Bacteriologist, and Amelia Cortés-Monllor, Assistant Bacteriologist, Agricultural Experiment Station, University of Puerto Rico, Rio Piedras 00928.  Phytopathology 65:401-403.

Field inoculations suggested that Xanthomonas bacteria pathogenic to southern pea (Vigna unguiculata) caused a bacterial blight of bean (Phaseolus vulgaris).  Isolation and cross-inoculation studies of bacteria from the two diseased host species suggest that two pathogenic types of Xanthomonas affect beans in Puerto Rico.  One type is pathogenic to bean only, while the other is pathogenic to both bean and southern pea.  In pathogenicity tests on bean and cowpea with 67 Puerto Rican Xanthomonas isolates from P. vulgaris and V. unguiculata, 56 were similar to X. vignicola (ATCC 11648), nine to X. phaseoli (ATCC 13464).  No differences in cultural, morphological, or physiological characters were apparent between isolates of the two pathogenic types.  It is suggested that Xanthomonas cultures that are pathogenic to both bean and southern pea should be regarded as X. vignicola, as originally suggested by Burkholder.

Additional key words: tropics, cowpea, strains.