Identification of Xanthomonas species associated with bacterial leaf spot of tomato, capsicum and chilli crops in eastern Australia

Several species of Xanthomonas cause bacterial leaf spot, a disease that affects solanaceous crops worldwide. The diversity of 64 Australian isolates of Xanthomonas spp. associated with bacterial leaf spot in tomato, capsicum and chilli crops in eastern Australia was determined using multi-locus sequence analysis of atpD, dnaK, efp and gyrB genes, species-specific PCR assays and biochemical analyses. At least five species of Xanthomonas associated with bacterial leaf spot were identified in Australian tomato, capsicum and chilli crops and their pathogenicity assessed. Phylogenetic and biochemical analyses identified X. euvesicatoria, X. perforans and X. vesicatoria as the most frequently recovered pathogenic species. Non-pathogenic and weakly pathogenic species were also identified. The suitability of the identification methods used and the implications of the detection of these species will be discussed.