Root rot and wilting complex of red raspberry in the Fraser Valley of British Columbia
Sapkota S. and Burlakoti R. R. 2021. Root rot and wilting complex of red raspberry in the Fraser Valley of British Columbia. British Columbia regional meeting, 2020/, Canadian Journal of Plant Pathology (Abstr.), 43:2, 337, DOI: 10.1080/07060661.2021.1889804.
Root rot and wilting complex (RRWC), primarily caused by Phytophthora spp., is the most important disease of red raspberry (Rubus idaeus) in British Columbia. However, very limited research has been conducted to understand the RRWC of red raspberry in the Fraser Valley of BC and causal agents associated with the disease complex. Therefore, we monitored several raspberry fields (n = 11) in 2018 and (n = 20) in 2019 in the Fraser Valley region from April to December to assess the disease complex. Diseased roots, canes and soil samples were collected multiple times each year and tested for the presence of Phytophthora using the Agdia immunostrip assay (Agdia Inc., Elkhart, IN, USA). Positive samples were further processed in the laboratory to isolate the causal agents using Phytophthora specific media and acidified potato dextrose agar. The isolates of suspected oomycetes were further characterized using pathogen morphology, species-specific PCR markers, ITS sequencing, and other sequence-based techniques. In both years, foliar symptoms, such as chlorosis, necrosis, leaf scorch, and wilting were observed in the majority of fields visited. Immunostrip assay showed that 55% and 75% of fields had Phytophthora positive samples in 2018 and 2019, respectively. Multiple species of Phytophthora including P. rubi, P. gonapodyides, and P. megasperma were detected from the infected samples. To confirm the pathogenicity, representative strains (n = 34) were inoculated on detached leaves of rhododendron. Preliminary results showed that 82% of isolates produced distinct lesions on rhododendron leaves. Detailed characterization of strains of Phytophthora is in progress.