title: Biochemical and molecular tools reveal two diverse Xanthomonas groups in bananas.
abstract: Xanthomonas campestris pv. musacearum (Xcm) causing the banana Xanthomonas wilt (BXW) disease has been the main xanthomonad associated with bananas in East and Central Africa based on phenotypic and biochemical characteristics. However, biochemical methods cannot effectively distinguish between pathogenic and non-pathogenic xanthomonads. In this study, gram-negative and yellow-pigmented mucoid bacteria were isolated from BXW symptomatic and symptomless bananas collected from different parts of Uganda. Biolog, Xcm-specific (GspDm), Xanthomonas vasicola species-specific (NZ085) and Xanthomonas genus-specific (X1623) primers in PCR, and sequencing of ITS region were used to identify and characterize the isolates. Biolog tests revealed several isolates as xanthomonads. The GspDm and NZ085 primers accurately identified three isolates from diseased bananas as Xcm and these were pathogenic when re-inoculated into bananas. DNA from more isolates than those amplified by GspDm and NZ085 primers were amplified by the X1623 primers implying they are xanthomonads, these were however non-pathogenic on bananas. In the 16-23 ITS sequence based phylogeny, the pathogenic bacteria clustered together with the Xcm reference strain, while the non-pathogenic xanthomonads isolated from both BXW symptomatic and symptomless bananas clustered with group I xanthomonads. The findings reveal dynamic Xanthomonas populations in bananas, which can easily be misrepresented by only using phenotyping and biochemical tests. A combination of tools provides the most accurate identity and characterization of these plant associated bacteria. The interactions between the pathogenic and non-pathogenic xanthomonads in bananas may pave way to understanding effect of microbial interactions on BXW disease development and offer clues to biocontrol of Xcm.
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Hoejbakkegaard Allé 3, 2630 Taastrup, Denmark; National Agricultural Research Laboratories, P. O. Box 7065, Kampala, Uganda. Electronic address: adrikoj@yahoo.com.
authors.forename: J
authors.initials: J
authors.lastname: Adriko
authors.affiliation: International Center for Tropical Agriculture (CIAT), P. O. Box 6247, Kampala, Uganda.
authors.forename: V
authors.initials: V
authors.lastname: Aritua
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Hoejbakkegaard Allé 3, 2630 Taastrup, Denmark.
authors.forename: C N
authors.initials: CN
authors.lastname: Mortensen
authors.affiliation: National Agricultural Research Laboratories, P. O. Box 7065, Kampala, Uganda.
authors.forename: W K
authors.initials: WK
authors.lastname: Tushemereirwe
authors.affiliation: National Agricultural Research Laboratories, P. O. Box 7065, Kampala, Uganda.
authors.forename: A L
authors.initials: AL
authors.lastname: Mulondo
authors.affiliation: National Agricultural Research Laboratories, P. O. Box 7065, Kampala, Uganda.
authors.forename: J
authors.initials: J
authors.lastname: Kubiriba
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Hoejbakkegaard Allé 3, 2630 Taastrup, Denmark.
authors.forename: O S
authors.initials: OS
authors.lastname: Lund
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D044822:Biodiversity; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D054884:Host-Pathogen Interactions; D028521:Musa / Q000382:microbiology*; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods; D013045:Species Specificity; D014454:Uganda; D014974:Xanthomonas / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D004275:DNA, Ribosomal
keywords: Biolog; Characterization; ITS sequencing; Phylogeny; Polymerase chain reaction; Xanthomonads