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

Abstract

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.Keywords amylolytic . pectolytic . Solanaceae . disease management IntroductionBacterial leaf spot (BLS) is a disease of solanaceous crops that occurs worldwide, especially in warm and humid climates (Jones et al. 2014). Several species of Xanthomonas are reported to cause BLS of tomato (Solanum lycopersicum), capsicum and chilli (Capsicum annuum) . The symptoms of BLS are small, brown, angular, water-soaked lesions on leaves, stems and fruit, and result in defoliation and direct fruit damage. Severe infection may result in extensive damage to crops with significant yield losses (Pernezny et al. 2003). Species reported to cause BLS all produce similar symptoms on their hosts, making precise diagnosis difficult from visual symptoms alone. The impact of pathological convergence and importance of phylogenetic testing in the case of BLS are further highlighted by Hajri et al. (2009). The causal bacteria are spread by wind and water, and may survive in crop residues, weeds and volunteer plants (Jones et al. 1986). A link between field disease and seed contamination has Eur J Plant Pathol (2018) 150:595-608

Pathological, Biochemical and Molecular Characterization of the Seed-Borne Bacteria "Pantoea Spp., Xanthomonas Spp. And Pseudomonas Spp." From Solanaceous Plants in Egypt

“…Results of the pathological behaviors of the isolated tomato seedborne bacteria, their cultural, morphological and physiological characters, as well as molecular techniques (16S rRNA gene sequence) were indicated that Pantoea ananatis was associated with graywall symptoms (Stall et al, 1970), Pseudomonas syringae pv. tomato was the causal agent of bacterial speck disease and Xanthomonas vesicatoria was associated with bacterial spot disease (Abd-Alla and Bashandy, 2008;Milijasevic etal., 2009 andOpara andOdibo 2009;Kolomiets et al, 2017;Roach et al, 2018). Re-isolation of artificially infected tomato plants indicated that P.ananatis was an endophytic seed-borne bacteria, these results were consistent with findings of Rijavec et al, (2007), while previous results were in contrast with Cota et al,…”

“…Wind-driven rain can contribute to more severe disease as the pathogens are splashed and spread to healthy leaves and fruit. The species-specific PCR assays, biochemical and serological analyses were used to identify the Xanthomonas species associated with bacterial leaf spot of tomato as diagnostic protocols for this disease (Manjula et al, 2017;Roach et al, 2018;Vancheva et al, 2018).Therefore, the present study was conducted to achieve the following objectives: to isolate the seed-borne bacterial pathogens from solanaceous plants collected from different locations in Egypt, to identify and characterize the isolated bacteria through cultural, biochemical tests and fatty acid profiling ,as well as, molecular techniques through 16S rRNA gene sequences.…”

Genome‐resolved metagenomics to study co‐occurrence patterns and intraspecific heterogeneity among plant pathogen metapopulations

“…is not uncommon in Alabama fields. In addition to P. cichorii , three tomato fields sampled in Macon and Tuscaloosa counties harboured significant populations of X. arboricola (relative abundance ranging from 2% to 11%), which is regarded as an opportunistic pathogen of tomato and pepper due to the strong pectolytic activity displayed by certain strains of this bacterial species (Vauterin et al ., ; Roach et al ., ).…”

Xanthomonas vesicatoria virulence factors involved in early stages of bacterial spot development in tomato

“…It is caused by at least four species of Xanthomonas : X. euvesicatoria , X. gardneri , X. perforans and X . vesicatoria (Stall, ; Strayer et al ., ; Roach et al ., ). The disease is characterized by necrotic lesions on leaves, stems and fruits, resulting in a reduction of yield and fruit quality (Potnis et al ., ).…”