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Authors Gorman

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Gorman, Christopher J.


Publications
2

CitationNamesAbstract
First report of ‘ Candidatus Phytoplasma trifolii’ and Spiroplasma citri in Cannabis sativa in Washington State, USA Wagstaff et al. (2026). Plant Disease Ca. Phytoplasma trifolii
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New Assays for Rapid Detection of Beet Leafhopper-Associated Plant Pathogens, ‘Candidatus Phytoplasma trifolii’, Beet Curly Top Virus, and Spiroplasma citri Swisher Grimm et al. (2023). Plant Disease 107 (12) Ca. Phytoplasma trifolii
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First report of ‘ Candidatus Phytoplasma trifolii’ and Spiroplasma citri in Cannabis sativa in Washington State, USA
In 2022 and 2024, field surveys were conducted in the Columbia Basin of Washington State, USA, for pathogens transmitted by the beet leafhopper, Circulifer tenellus, including beet curly top virus (BCTV), ‘Candidatus Phytoplasma trifolii’ (CPt), and Spiroplasma citri (S. citri). For these pathogens, an association of symptoms with a causal agent is often complicated by co-infections and the inability to culture CPt (Hu 2021; Rivedal et al. 2022, 2024; Schoener & Wang 2023). In 2022, 35 hemp (Cannabis sativa) plants were observed at the Washington State University (WSU) Research Station in Othello, WA, with typical symptoms of BCTV (a finding published by Jarugula et al. 2023) and we further tested these samples for C. tenellus-associated bacteria. In 2024, 23 and 15 hemp plants observed in Prosser, WA, from the WSU Irrigated Agriculture Research Center and WSU Roza Farm, respectively, with symptoms of CPt infection, including stem fasciation and purpling. Leaf tissue from each plant was ground in liquid nitrogen, DNA extracted using the DNeasy Plant Mini Kit (Qiagen, Inc.), and a multiplex real-time PCR protocol used to detect the C. tenellus-associated pathogens (Swisher Grimm et al. 2023). CPt was identified in 8.6% and 65.8% of plants in 2022 and 2024, respectively, while S. citri was not detected in 2022 but was found in 15.8% of plants in 2024. Co-infections were common. Nested PCR (primers P1/P7 and R16F2n/R16R2, Crosslin et al. 2006) and conventional PCR (primers Trif-SecY-163F, 5ʹ-AGCAGCTAAAAAAGTTAGAAAAAACCTC-3ʹ/Trif-SecY-1040R, 5ʹ-AAATCTAGCGAAAATGATTTTTTGTTTTCA-3ʹ) targeted the CPt 16S rRNA and secY genes, respectively. S. citri infection was confirmed by PCR targeting the spiralin gene (primers SpiralinF/R, Yokomi et al. 2008). All targets were amplified using PrimeSTAR HS DNA polymerase (Takara Bio Inc.). Thermal cycle conditions for CPt 16S rRNA and S. citri spiralin genes consisted of 30 or 40 cycles, respectively, at 98°C for 10 s, 55°C for 15 s, and 72°C for 10 s, followed by a final elongation at 72°C for 5 min. Conditions for CPt secY consisted of 35 cycles at 98°C for 15 s, 55°C for 30 s, and 72°C for 10 s, followed by a final elongation at 72°C for 5 min. Amplicons of size 1,250 bp, 877 bp, and 675 bp for the 16S rRNA, secY, and spiralin genes, respectively, were visualized on an agarose gel stained with GelRed (Sigma-Aldrich) or Ethidium Bromide. For CPt, sequencing of 16S rRNA from seven infected samples (2 from 2022, 5 from 2024) revealed identical sequences (GenBank Accession PV983691) with 100% identity to CPt in U.S. hemp (OQ597521), and sequencing of secY in one sample from 2022 and one from 2024 revealed identical sequences (PX725980), with 100% identity to CPt in U.S. periwinkle (GU004317). For S. citri, two sequenced samples had identical spiralin sequences (PV955037), matching 100% and 99.85% with S. citri found in Oregon cabbage (PV099668) and hemp (OQ969984), respectively. This is the first confirmed report of CPt and S. citri in C. sativa in Washington state. These findings highlight the need to evaluate effects of mollicutes on hemp and underscore the need to develop integrated pest management strategies to reduce vector transmission. In addition, these findings suggest that hemp could serve as a reservoir of the C. tenellus-transmitted pathogens, leading to higher pathogen prevalence across the region, and negatively impacting economically important vegetable and seed crops grown in Washington state that are susceptible to these pathogens.
New Assays for Rapid Detection of Beet Leafhopper-Associated Plant Pathogens, ‘Candidatus Phytoplasma trifolii’, Beet Curly Top Virus, and Spiroplasma citri
The beet leafhopper Circulifer tenellus is an important pest of agricultural crops in the United States, where it transmits beet curly top virus, beet leafhopper-transmitted virescence agent phytoplasma, and Spiroplasma citri to numerous crops, affecting yield and quality. Each of these pathogens have been linked to serious disease outbreaks within Washington State in the past century. To mitigate the risk of disease, growers target the beet leafhopper in their insect pest management programs. Knowledge of pathogen prevalence in beet leafhopper populations could help growers make better management decisions, but timely diagnostics is required. Four new assays were developed for the rapid detection of the beet leafhopper-associated pathogens. These include two assays that detect Beet leafhopper transmitted virescence agent (a PCR and a real-time PCR SYBR green assay), a duplex PCR assay that simultaneously detects beet curly top virus and Spiroplasma citri, and a multiplex real-time PCR assay for the simultaneous detection of all three pathogens. The screening of dilution series generated from plant total nucleic acid extracts with these new assays typically led to detection at levels 10- to 100-fold more sensitive than the conventional PCR assays currently used. These new tools will allow the rapid detection of beet leafhopper-associated pathogens in both plant and insect specimens and will have the potential to be used in diagnostic laboratories seeking to disseminate fast and accurate results to growers for implementation in their insect pest monitoring programs.
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