Xanthomonas arboricola pathovar pruni - bacterial pathogen of plants
Background
Xanthomonas arboricola pv. pruni (XAP) is a bacterial pathogen that infects a range of Prunus species, including peaches, almonds and Japanese plums. As an EPPO A2 quarantine organism, it presents a significant threat to commercial fruit production. Infection can lead to:
unmarketable fruit - cracks and necrotic spots result in rejection during grading.
weakened trees - premature leaf drop reduces fruit size, weight, and quality, weakening affected orchards.
Spread of XAP across Europe
Originally confined to Italy and France, XAP has spread across Europe since 2014, with frequent outbreaks on Prunus laurocerasus. In the UK, outbreaks are often linked to nursery interceptions, with recurrent infections detected over a number of years.
Economic impact
XAP has caused substantial economic losses internationally.
Examples include:
Italy: Losses exceeding €10,000 per hectare, with between 25% to 75% of peach fruit becoming unmarketable during severe outbreaks.
Australia: Estimated annual losses of AUS $3.1 million
Spain: Almond production losses of 23 to 46% during major outbreaks
Genomic surveillance for disease management
Whole genome sequencing (WGS) can address critical management challenges:
determining If outbreaks in nurseries are persistent or due to new infections.
identifying epidemiological links between UK outbreaks to determine whether they are connected or because of separate introductions.
differentiating between pathogenic XAP and non-pathogenic X. arboricola strains, by reducing unnecessary regulatory actions.
confirming species identity and plasmid presence, crucial for identifying pathogenic strains.
The investigation was supported by FERA's collection of ~90 XAP isolates from the UK and Europe, along with other X. arboricola isolates. These tools can be applied to other bacterial plant pathogens, enhancing plant disease management strategies.