First report of citrus canker caused by Xanthomonas campestris pv. citri on Citrus sinensis in Bolivia

Xanthomonas campestris pv. citri Dye 1978 (X. axonopodis pv. citri (Hasse 1915) Vauterin, Hoste, Kersters & Swings 1995) is the causal agent of citrus canker. In South America the disease has been reported from Argentina, Brazil, Chile, Paraguay and Uruguay. During 1999-2000, lesions were observed on leaves, twigs and fruits on cultivated citrus in the Cochabamba and Santa Cruz Departments. Lesions were yellow/brown, raised and corky: these darkened and developed central depressions with age. The edges of the lesions remained raised and were frequently surrounded by a chlorotic halo. Gram negative bacteria producing yellow-pigmented, mucoid colonies on yeast dextrose agar were consistently isolated from the leaf lesions. Pathogenicity testing was conducted on potted Citrus x Citrofortunella mitis (calamondin) plants. Water-soaked lesions, 2-3 mm in diameter, developed at the inoculation sites after 10 days and the bacteria were consistently re-isolated from the affected tissues. Fatty acid profiles obtained from isolates were typical of the genus Xanthomonas (Saddler & Bradbury, 2001). Additional testing with taxon-specific polymerase chain reaction (PCR) primers (Miyoshi et al., 1998), repetitive sequence PCR fingerprinting (Rep-PCR), AFLP and carbon source utilisation patterns (Biolog, Hayward, CA) were conducted alongside known strains of X. campestris pv. citri. The results obtained from the Bolivian isolates using taxon-specific PCR and Biolog were consistent with membership of X. campestris pv. citri (Miyoshi et al., 1998; Verniere et al., 1993). These findings were further corroborated by the fingerprinting studies which highlighted close similarities between the isolates and named reference material. Isolates have been placed in the IMI culture collection, CABI Bioscience, UK (IMI 385155, IMI 185156 & IMI 385157). Although citrus canker has been suspected in Bolivia for a number of years, this is the first confirmed report.