Bacterial leaf spot (BLS) is a disease of tomato, chilli and capsicum caused by four species of Xanthomonas. BLS can cause severe crop damage and is a limiting factor of production across the world.

1. biosecurity built on science
Detection and identification of
Australian Xanthomonas species
causing bacterial leaf spot
Rebecca Roach
PhD student
Plant Biosecurity Cooperative Research Centre

2. biosecurity built on science
Background
Bacterial leaf spot
(BLS)
Four common species:
 X. vesicatoria
 X. euvesicatoria
 X. perforans
 X. gardneri
Which species
cause BLS in
Australia?

3. biosecurity built on science
Project aims
 Which bacterial species cause BLS in Australia?
 How are these species distributed?
→Characterise with MLSA and biochemical analyses
 How diverse are these pathogen populations?
 How does pathogenicity vary?
→Investigate with whole genome sequences
= Improved disease management

4. biosecurity built on science
Collection and characterisation
 Isolates sourced from
tomato, capsicum and
chilli crops
 Biochemical analyses:
oxidase, catalase, KOH
(gram reaction), starch,
pectin, YDC
 Specific PCR
 MLSA of 64 isolates –
gyrB, efp, dnaK, atpD

5. biosecurity built on science
Genomic analysis
44 genomes of collected Xanthomonas isolates
 Whole genome phylogeny
 Pan-genome analysis
 Average nucleotide identity
 Cazyme analysis
 Effector protein repertoires
 Plasmid diversity

6. biosecurity built on science
Race trials
 Differential lines in
capsicum contain
resistance genes
 Assign races to
collected Xanthomonas
isolates
 Results inform disease
management

7. biosecurity built on science
Impact of findings
 Diversity, pathogenicity and distribution
inform management strategies
 Project will result in framework for
detecting and understanding xanthomonas
pathogens
 This will be applicable to exotic species

8. biosecurity built on science
Thank you
Epic team:
Dr. Brendan Rodoni, Dr. Rachel
Mann, Dr. Cherie Gambley, Dr.
Roger Shivas, Dr. Toni Chapman
Agribio/ La Trobe University,
QDAF, PBCRC, HIA
For more information, please
email
roach.r@students.latrobe.edu.au