Xylella fastidiosa Outbreak in Israel: Population Genetics, Host Range, and Temporal and Spatial Distribution...

Area of Science:

• Plant Pathology
• Bacteriology
• Genomics

Background:

• Xylella fastidiosa causes significant plant diseases globally, including almond leaf scorch (ALS).
• ALS was first reported in Israel in 2017, prompting investigation into its origins and spread.
• Previous outbreaks in the Americas and Europe highlight the economic impact of Xylella fastidiosa.

Purpose of the Study:

• To identify the causal agent of ALS in Israel.
• To determine the genetic diversity and host range of the pathogen.
• To analyze the temporal and spatial distribution of ALS in Israel.

Main Methods:

• Isolation and mechanical inoculation of Xylella fastidiosa from symptomatic almond trees.
• Genomic analysis of local Xylella fastidiosa isolates.
• Disease distribution mapping from 2017 to 2020.

Main Results:

• Xylella fastidiosa subsp. fastidiosa sequence type 1 was confirmed as the causal agent of ALS in Israel.
• The pathogen successfully infected almond and grapevine but not other tested fruit species.
• Genomic data suggests a single introduction of the pathogen, related to Californian grapevine strains.
• ALS spread was limited initially but showed expansion from 2020 onwards, with clustered and row-based patterns.

Conclusions:

• Xylella fastidiosa is definitively confirmed as the cause of ALS in Israel.
• The pathogen's host range is primarily almond and grapevine, posing a threat to these industries.
• Understanding the spread patterns is crucial for managing future outbreaks, despite vector identity remaining unclear.