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The Causal Organism of Bacterial Black Spot of Mangoes. P. L. Steyn, Department of Microbiology-Plant Pathology, Faculty of Agricultural Sciences, University of Pretoria, Pretoria, 0001, Republic of South Africa; N. M. Viljoen(2), and J. M. Kotzé(3). (2)Research Institute for Plant Pathology, Private Bag X134, Pretoria, 0001, Republic of South Africa; (3)Department of Microbiology-Plant Pathology, Faculty of Agricultural Sciences, University of Pretoria, Pretoria, 0001, Republic of South Africa. Phytopathology 64:1400-1404. Accepted for publication 3 June 1974. DOI: 10.1094/Phyto-64-1400.

The pathogen of bacterial black spot of mangoes (Mangifera indica) in South Africa was isolated and subjected to a series of pathogenicity and diagnostic tests together with two isolates of Pseudomonas mangiferaeindicae, one of Erwinia mangiferae and a yellow-pigmented bacterium isolated from old fruit lesions. The pathogen was identified as P. mangiferaeindicae and found to be identical to the two isolates included for comparison. The yellow-pigmented organism was found to be identical to E. mangiferae, but neither of the two isolates was pathogenic to mangoes. It was concluded that E. mangiferae had never been responsible for bacterial black spot of mangoes and that P. mangiferaeindicae was the causal agent for all outbreaks of this disease in South Africa, India, and Pakistan. It is suggested that the official description of P. mangiferaeindicae be amended and extended, and that this species be removed from the fluorescent group in the key for the identification of species of the genus Pseudomonas.