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Comparative Growth of Xanthomonas phaseoli and Xanthomonas vesicatoria and Development of Symptoms in Bean and Tomato Leaves. Shih -Tien Hsu, Graduate Student, Department of Plant Pathology, Cornell University, Ithaca, New York 14850, Present address of senior author: Department of Plant Pathology, National Chung Hsing University, Taichung, Taiwan, Republic of China; Robert S. Dickey, Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 62:329-332. Accepted for publication 18 October 1971. DOI: 10.1094/Phyto-62-329.

The growth patterns of Xanthomonas phaseoli and Xanthomonas vesicatoria in their natural hosts, bean and tomato, respectively, were similar. After inoculation by the injection-infiltration method, populations of the bacteria initially increased rapidly in the leaves, then gradually decreased. The maximal numbers of the pathogens in the leaves was attained more rapidly after inoculation with 108 cells/ml than with 106 cells/ml, and tissue necrosis appeared when the populations reached the maxima. The population trends of X. phaseoli and X. vesicatoria in their nonhosts, tomato and bean, respectively, were different. The population of X. phaseoli decreased rapidly in tomato leaves, whereas the population of X. vesicatoria increased in bean leaves. Both bacteria induced visible necrosis in leaves of their nonhost plants at an inoculum concentration of 108 cells/ml, but not at 106 cells/ml. Xanthomonas phaseoli caused a rapid development of necrosis in tomato leaves, whereas X. vesicatoria caused a slow development of necrosis in bean leaves.

Additional keywords: Phaseolus vulgaris, Lycopersicon esculentum.