APS Homepage

Poster: Diseases of Plants: New & Emerging Diseases


Bacterial black spot of mango, Mangifera indica, caused by Xanthomonas citri pv mangiferaeindicae, is confirmed in the Western Hemisphere
G. SANAHUJA (1), R. Ploetz (1), P. Lopez (1), J. Konkol (1), A. Palamateer (1) (1) University of Florida, U.S.A.

During the summer of 2015, symptoms of what appeared to be bacterial black spot (BBS) were observed on mature fruits of mango, Mangifera indica, in the vicinity of Boynton Beach, FL. Star-shaped lesions, up to 2 cm in diameter, erupted from the surface of ‘Keitt’ and other cultivars, and oozed a sticky, clear exudate. From lesions, a cream-colored bacterium was recovered on YPGA and characterized with housekeeping genes used by Bui Thi Ngoc et al. (2010) (efp and dnaK). Amplicons from a representative isolate were sequenced (KU746336 and KU746337) and were 100% homologous with strains of Xanthomonas citri pv mangiferaeindicae (Xcm) in GenBank. ML analysis (Tamura-Nei model) with MEGA 6.06 placed the isolate among other strains of Xcm. In incubator studies (30oC day, 26oC night, 12h light), the mesophyll of leaves on potted ‘Keitt’ and ‘Haden’ plants were injected with a hypodermic needle and 1 x 105 CFU mL-1 of the isolate. After 7 days, black lesions developed on inoculated leaves, but not on leaves injected with sterile deionized H2O. Diagnostic amplicons for Xcm were generated for isolates recovered from the lesions, and the experiment was conducted twice. BBS is widespread in the Eastern Hemisphere, but this is the first report of the disease in the Western Hemisphere. Environmental conditions in southern Florida appear to be ideal for an increased importance of BBS in the region.