All commercially cultivated European grapevines (Vitis vinifera) are considered susceptible to Pierces disease (PD) caused by the xylem-limited bacterium Xylella fastidiosa (Wilcox et al. 2015). PD causes vine losses and is the primary limiting factor to grape production in Texas (Perry Cesbron et al. 2023) following manufacturer’s protocol. Both methods yielded similar results, finding positive tests for X. fastidiosa in 9 of the 12 samples. Isolation attempts were successful in 6 of 11 samples representing all tested cultivars. qPCR of pure cultures confirmed the isolates as X. fastidiosa (Shaad et al. 2002). To further characterize the pathogen, bacteria were isolated from fresh samples from positive AB, EN and PN plants. Isolates were cultured on PWG media and DNA extracted from single clones using the Monarch genomic DNA kit (NEB, Ipswich, MA). Sequencing and genome assembly was done following Vanhove et al. 2019. LINgroup (Tian et al. 2020) and MLST (Jolley et al. 2018) sequence comparisons placed all strains in the ST1 group of X. fastidiosa subsp. fastidiosa; strains clustered most closely to CCPM1, an X. fastidiosa subsp. fastidiosa genome from Georgia, USA (NCBI accession SAMN09941435). All sequences were deposited to NCBI bioproject PRJNA1278688 under accessions PDTx24C284: SAMN49192511 (PN), PDTx24C281: SAMN49192510 (EN), and PDTx24C279: SAMN49192509 (AB). PD symptomatology, positive identification of X. fastidiosa by RPA and qPCR, pathogen isolation and whole genome sequencing, warrant a report on these cultivars. We believe this is the first report of X. fastidiosa associated with these cultivars under field conditions in Texas. The consistent presence of X. fastidiosa, and PD symptoms at this site, raises significant concerns about the role these varieties may play, as pathogen reservoirs and the resulting impact on grapevine planting recommendations. The consequences of these observations to the spread and management of PD are not fully understood and continued investigation of their resistance traits is encouraged.
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