Xanthomonas campestris pv. campestris race 1 is the main causal agent of black rot of Brassicas in Southern Mozambique

摘要

Severe outbreaks of bacterial black rot caused by?Xanthomonas campestris?pv.campestris?(Xcc) were observed in?Brassica?production fields of Southern Mozambique. The causal agent of the disease in the Mahotas and Chòkwé districts was identified and characterised.?In total, 83?Xanthomonas-like strains were isolated from seed samples and leaves of?cabbage and tronchuda cole?with typical symptoms of the disease.?Forty-six out of the 83 strains were found to be putative?Xcc?in at least one of the tests used: Classical?biochemical assays,?enzyme-linked immunosorbent assay (ELISA)?with monoclonal antibodies, Biolog identification system, polymerase chain reaction (PCR) with specific primers and pathogenicity tests.?The ELISA tests were positive for 43 strains. Biolog identified 43 strains as?Xanthomonas, but only 32 as?Xcc. PCR tests with primers targeting a fragment of the?hrpF?gene were positive for all 46 strains tested. Three strains were not pathogenic or weakly pathogenic and all other strains caused typical black rot symptoms in brassicas. Race type differentiation tests revealed the?Xcc?strains from Mozambique as members of race 1. The prevalence of this pathogenic race of the?Xcc?pathogen in Mozambique should be considered when black rot resistant cultivars are evaluated or introduced into the production regions of this country.