First report of <i>Phytopythium vexans and Phytopythium litorale</i> associated with root rot symptoms on red raspberry (<i>Rubus idaeus</i>)

Twenty-two root samples from raspberry plants exhibiting symptoms consistent with Phytophthora infection, i.e. cane wilt, chlorotic leaves, and blackened roots, were collected two farms in Perthshire, Scotland, November 2021 (Fig. 1). Roots rinsed water, cut into 20 mm sections, transferred 70% (v/v) ethanol for 10 seconds dried on sterile filter paper. Five sections per sample aseptically to Petri dishes containing CMA-PARP medium (Stewart et al., 2014), sealed incubated the dark at 18°C. The hyphal tips of growing colonies onto fresh CMA-PARP. isolates obtained, distinct morphotypes: one produced sub-globose, non- semi-papillate sporangia, while second globose papillate sporangia 2). Root material (c. 1–2 g sample) was freeze-dried 2 mL microfuge tubes prior DNA extraction a PowerSoil Pro Kit (Qiagen, Germany) as manufacturer's instructions. PCR performed using genus-specific primer pair YPh1F/YPh2R (Schena 2008). species P. idaei, ilicis plurivora detected but no these obtained samples. To determine identity isolates, ITS region amplified sequenced ITS5 ITS4 primers (White 1990). BLAST analysis revealed isolate 99.49% Phytopythium vexans found China (GenBank Accession No. MW800643). A fragment 860 bp deposited GenBank (OQ170787). Four further had 99.54% sequence litorale Chile (KU961896.1). 662 (OQ449690). Metabarcoding Scibetta al. (2012) Pp. 81% 63% samples, respectively. detached assay, healthy year old cv. Tulameen, performed. water submerged minute, twice distilled water. placed paper 500 μL dishes, replicates isolate. basal section each suspended 1.5 tube plastic film prevent drying. apical portion wounded needle 5 1×104 zoospore/mL suspension pipetted wound. 20°C 14 days 3). Black lesions noted zone roots inoculated vexans, remained healthy. caused throughout entire root. Both re-isolated diseased method above. co-detection may suggest both genera are involved rot sites. have been reported strawberry Czech Republic by Pánek & Střížková (2021). This is first report pathogenicity red raspberry. authors acknowledge Katherine Stewart, Georgina Fagg Jennifer Kingsnorth their assistance. work carried out part Collaborative Training Partnership Fruit Crop Research (CTP-FCR) programme; code CTP-FCR-2020-9 funded AHDB BSPP.