Polyphasic characterization, pathogenicity and host range of Neocamarosporium betae causing quinoa stem rot in Saskatchewan, Canada

Abstract

Neocamarosporium betae is a seed-borne pathogen that persists in crop residues within Prairie agroecosystems, yet its impact on quinoa production remains poorly understood. This study used a polyphasic approach to clarify the taxonomic identity and epidemiological risks of isolates recovered from symptomatic quinoa stems in Saskatchewan, Canada. Thirty-eight isolates were obtained, all displaying morphology consistent with Neocamarosporium spp. Detailed characterization of six representative isolates showed conserved micromorphological traits, including conidial dimensions and pycnidial structure. Phylogenetic analyses based on ITS sequences, supported by a three‑locus MLSA of representative isolates, resolved all isolates within a robust monophyletic clade corresponding to N. betae. A subset of isolates (IMSS400, IMSS432, IMSS438, IMSS440, IMSS450, IMSS452) was used in pathogenicity and host-range assays. Pathogenicity assays revealed significant isolate-cultivar interactions; N. betae isolates IMSS450 and IMSS452 were the most aggressive, causing up to 62% disease incidence on cultivars NQWhite and NQRed, whereas NQBlack exhibited isolate-dependent resistance. Host-range assays demonstrated spillover potential into faba bean (40% incidence) and pea, while canola displayed strong non-host resistance. Seed-borne assays showed germination reductions from >91% in controls to 43%, primarily driven by isolates IMSS400 and IMSS450. IMSS400 exhibited pathogenicity restricted to early seedling development. These findings provide actionable insight for cultivar selection based on pathogenicity of isolates and underscore the need for seed‑health interventions to reduce early‑season losses caused by N. betae.