First Report of leaf scorch of Poison ivy ( Toxicodendron radicans ) caused by Xylella fastidiosa in Virginia

Xylella fastidiosa (Xf) is a xylem-limited bacterial pathogen belonging to the Xanthomonadaceae family and is transmitted by xylem-feeding insects. It has been found in more than 720 plant species and is associated with major diseases including Pierce’s disease of grapevine and leaf scorch in several woody hosts whereby Xf. subsp. fastidiosa (Xff) and subsp. multiplex (Xfm) have both been found to cause Pierce's Disease in Virginia (Abdelrazek et al. 2024). Poison ivy (Toxicodendron radicans), a deciduous woody vine native to North America, occurs widely in agricultural and natural landscapes. In September 2025, a poison ivy climbing an oak tree at the edge of a vineyard with confirmed Xff infection, exhibited leaf scorch symptoms characterized by marginal chlorosis and brown necrotic lesions, consistent with those associated with Xf infection in grapevine and oaks hosts. Three symptomatic leaves were collected, and petiole tissue (~1g) was subjected to DNA extraction using the Bioline Isolate II genomic DNA kit. Detection of X. fastidiosa was performed by real-time qPCR (Harper et al., 2010), yielding Cq values of 18.3 (undiluted) and 21.9 (10× dilution), well below the detection threshold (Cq ≈ 35), indicating a high bacterial load in symptomatic tissues. DNA was submitted to SeqCenter (Pittsburgh, PA, USA) for Illumina metagenomic sequencing (150 bp paired end reads) on a NovaSeq X Plus platform. A total of 25.9 million paired-end reads were generated. Taxonomic classification was performed using Kraken2 (Wood et al. 2019) with the PlusPF database (release 2026-02-26), which includes prokaryotes, viruses, fungi, and protozoa, revealed that Xf was the most abundant microbial taxon, with no other plant pathogens being detected. When using a custom Kraken2 database containing the Xff and Xfm subspecies, 0.96% of reads were assigned to Xfm and 0.33% to Xff, suggesting the presence of Xfm although co-infection with Xff could not be excluded. To independently confirm subspecies identity, raw reads were mapped to the Xfm Griffin-1 reference genome (GCF_000466025.1) using Bowtie2 (Langmead and Salzberg 2012), followed by assembly using SPAdes (Prjibelski et al. 2020). The resulting metagenome-assembled genome (MAG) had a length of 2.38 Mb, consisted of 126 contigs, showed 99.64% completeness with 0% contamination based on CheckM (Parks et al. 2015) and was submitted to NCBI (GenBank: JBVOUK000000000). The MAG exhibited 99.39% ANI to Xfm ATCC 35871 (GCF_000428665.1), originally isolated from hybrid plum in Georgia, using genomeRxiv (https://genomerxiv.cs.vt.edu/index.php), confirming its identity as Xfm. Finally, multilocus sequence typing was performed by querying the seven-gene scheme via the PubMLST online platform, which identified the MAG as sequence type (ST) 8, an ST that belongs to Xfm (Jolley et al. 2018). To our knowledge, this is the first report of Xf infecting poison ivy. The detection of a new host species next to a vineyard known to be infected with Xf highlights the potential role of native vegetation as reservoir contributing to sustained inoculum pressure on grapevines. While the Xf subspecies infecting the vineyard has not yet been fully characterized. these findings emphasize the importance of considering wild plant communities in Xf surveillance, vector management, and the design of buffer zones to reduce pathogen spillover risks in viticultural landscapes.