@article {4727, title = {First report of the NA2 clonal lineage of the sudden oak death pathogen, Phytophthora ramorum, infecting tanoak in Oregon forests}, journal = {Plant Disease}, year = {2022}, month = {Feb-02-2022}, abstract = {

Phytophthora ramorum Werres, de Cock \& Man in{\textquoteright}t Veld, causal agent of sudden oak death (SOD) and ramorum leaf blight, is comprised of four clonal lineages in its invasive ranges of North America and Europe (Gr{\"u}nwald et al. 2012, Van Poucke et al. 2012). Of these, three {\textendash} the NA1, NA2, and EU1 lineages {\textendash} are found in U.S. nurseries, but only two, the NA1 and EU1 lineages, have been found infecting trees in North American forests (Gr{\"u}nwald et al. 2012, 2016). In the spring of 2021, tanoak (Notholithocarpus densiflorus Manos, Cannon \& Oh) displaying symptoms consistent with SOD were detected north of Port Orford (Curry County, Oregon). Symptoms were canopy dieback and blackened petiole and stem lesions on tanoak sprouts. The pathogen isolated on PAR (CMA plus 200 ml/L ampicillin, 10 mg/L rifamycin, 66.7 mg/L PCNB) selective media was determined to be P. ramorum based on characteristic morphology of hyphae, sporangia, and chlamydospores (Werres et al. 2001). Positive identification as P. ramorum was obtained with a lineage-specific LAMP assay targeting an NA2 orphan gene, indicating the presence of the NA2 lineage. NA2 was confirmed by sequencing a portion of the cellulose binding elicitor lectin (CBEL) gene using CBEL5U and CBEL6L primers (Gagnon et al. 2014). Sequences (GenBank accessions MZ733981 and MZ733982) were aligned against reference sequences for all lineages (Gagnon et al. 2014) confirming the presence of NA2. Lineage determination as NA2 was further confirmed at eleven SSR loci (ILVOPrMS145, PrMS39, PrMS9C3, ILVOPrMS79, KI18, KI64, PrMS45, PrMS6, ILVOPrMS131, KI82ab, and PrMS43) using the methods of Kamvar et al. (2015). We completed Koch{\textquoteright}s postulates using potted tanoaks, wound-inoculated at the midpoint of 1-year old stems with either hyphal plugs or non-colonized agar (n=4 per treatment). Tanoaks were maintained in a growth chamber (20{\textdegree}C-day / 18{\textdegree}C-night temperatures) with regular watering and an 18-photoperiod using F32T8 fluorescent bulbs (Phillips, Eindhoven, The Netherlands). After 7 days, brown to black lesions 1.2 to 2.9 cm in length were observed on the inoculated stems, from which P. ramorum was subsequently re-isolated; no symptoms were observed on the controls, and no pathogens were recovered when plating the wound sites in PAR. This is the first detection of the NA2 lineage causing disease in forests worldwide. The outbreak was found on private and public lands in forests typical to the SOD outbreak in Oregon (mixed conifer and tanoak), and was 33 km north of the closest known P. ramorum infestation. Follow-up ground surveys on adjacent lands have identified over 100 P. ramorum-positive tanoak trees, from which additional NA2 isolates have been recovered from bole cankers. NA2 is thought to be more aggressive than the NA1 lineage (Elliott et al. 2011), which has been present in Curry County since the mid-1990s (Goheen et al. 2017). Eradication of the NA2 lineage is being pursued to slow its further spread and prevent overlap with existing NA1 and EU1 populations. The repeated introductions of novel lineages into the western United States native plant communities highlights the vulnerability of this region to Phytophthora establishment, justifying continued monitoring for P. ramorum in nurseries and forests. References {\textbullet} Elliott, M, et al. 2011. For. Path. 41:7. https://doi.org/10.1111/j.1439-0329.2009.00627.x {\textbullet} Gagnon, M.-C., et al. 2014. Can. J. Plant Pathol. 36:367. https://doi.org/10.1080/07060661.2014.924999 {\textbullet} Goheen, E.M., et al. 2017. For. Phytophthoras 7:45. https://doi: 10.5399/osu/fp.7.1.4030 {\textbullet} Gr{\"u}nwald, N. J., et al. 2012. Trends Microbiol. 20:131. https://doi.org/10.1016/j.tim.2011.12.006 {\textbullet} Gr{\"u}nwald, N. J., et al. 2016. Plant Dis. 100:1024. https://doi.org/10.1094/PDIS-10-15-1169-PDN {\textbullet} Kamvar, Z.N. et al. 2015. Phytopath. 105:982. https://doi.org/10.1094/PHYTO-12-14-0350-FI {\textbullet} Van Poucke, K., et al. 2012. Fungal Biol. 116:1178. https://doi.org/10.1016/j.funbio.2012.09.003 {\textbullet} Werres, S., et al. 2001. Mycol. Res. 105: 1155. https://doi.org/10.1016/S0953-7562(08)61986-3

}, issn = {0191-2917}, doi = {10.1094/PDIS-10-21-2152-PDN}, url = {https://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-10-21-2152-PDN}, author = {Peterson, Ebba K. and Sondreli, Kelsey Liann and Reeser, Paul and Navarro, Sarah M. and Nichols, Casara and Wiese, Randall and Fieland, Valerie and Gr{\"u}nwald, Niklaus J. and LeBoldus, Jared M.} } @article {4692, title = {Root Rot of Juniperus and Microbiota by Phytophthora lateralis in Oregon Horticultural Nurseries}, journal = {Plant Disease}, volume = {104}, year = {2020}, month = {Jan-05-2020}, pages = {1500 - 1506}, abstract = {

Widespread symptoms of root rot and mortality on Juniperus communis and Microbiota decussata were observed in two horticultural nurseries in Oregon, leading to the isolation of a Phytophthora sp. from diseased roots. Based on morphology and sequencing the internal transcribed spacer ITS1-5.8S-ITS2 region, isolates were identified as the invasive pathogen Phytophthora lateralis, causal agent of Port-Orford-cedar (POC; Chamaecyparis lawsoniana) root disease. Additional sequencing of the cytochrome c oxidase subunit 1 and 2 genes identified all isolates as belonging to the PNW lineage. Utilizing recovered isolates plus a POC-wildlands isolate and susceptible POC as controls, we completed Koch{\textquoteright}s postulates on potted Juniperus and Microbiota plants. Nursery isolates were more aggressive than the forest isolate, which was used in the POC resistance breeding program. Increased aggressiveness was confirmed using a branch stem dip assay with four POC clones that differed in resistance, although no isolate completely overcame major-gene resistance. Isolates were sensitive to mefenoxam, a fungicide commonly used to suppress Phytophthora spp. growth in commercial nurseries. Although POC resistance is durable against these more aggressive nursery isolates, the expanded host range of P. lateralis challenges POC conservation through the continued movement of P. lateralis by the nursery industry.

}, issn = {0191-2917}, doi = {10.1094/PDIS-04-19-0808-RE}, url = {https://apsjournals.apsnet.org/doi/10.1094/PDIS-04-19-0808-RE}, author = {Peterson, Ebba K. and Rupp, Franziska and Eberhart, Joyce and Parke, Jennifer L.} }