Morpho-Molecular Identification and Race Detection of Xanthomonas campestris pv. campestris Causing Black Rot Disease of Cabbage in Bangladesh

Black rot disease, caused by the seed-borne bacterial pathogen Xanthomonas campestris pv. campestris (Xcc), reduces cabbage yield, featuring V-shaped chlorotic lesions along leaf margins. In December 2024, typical black rot symptoms were observed on cabbage plants in Churamonkathi Union, Jessore District, Bangladesh. Bacteria isolated from symptomatic leaf tissues on King’s medium B base agar were consistent with Xcc based on morphological and biochemical characteristics. Pathogenicity was confirmed by Koch’s postulates, with characteristic symptoms reproduced on healthy cabbage plants 7–14 days after inoculation (DAI). These pathogenic isolates were consolidated as Xcc by Xcc-specific primers (Xcc_53F/R). Subsequently, race determination using race-specific primers revealed that all pathogenic isolates belonged to race 1, as the primer pair Xcc_R2_89.2 F/R produced a 1523 bp amplicon. Partial 16S rRNA gene sequencing of one representative isolate and phylogenetic analysis confirmed its identity as Xcc. This study provides the morpho-molecular confirmation and race detection of Xcc race 1 causing black rot on cabbage in Bangladesh, where the pathogen was previously reported only from mustard seeds without detailed characterization. The findings will facilitate the development of effective disease management strategies for sustainable cabbage production in the country.