Frequent recovery of Sydowia polyspora from brown spot needle blight-associated loblolly pine (Pinus taeda) needles in Alabama

Temitope Folorunso, Gabriel Silva, Rabiu Olatinwo, Lori Eckhardt, Hao Chen, Janna Willoughby 

Sydowia polyspora is a widespread conifer-associated fungus that can function as an endophyte, saprophyte, or opportunistic pathogen, but its occurrence in southeastern pine systems remains poorly characterized. During surveys of symptomatic loblolly pine (Pinus taeda) in Washington and Cullman counties, Alabama, fungal isolates morphologically consistent with Sydowia spp. were recovered from needles exhibiting foliar disease symptoms. Isolates were characterized using colony morphology, microscopy, ITS sequencing, translation elongation factor 1-alpha (EF1-α) sequencing, species-specific EF1-α primers, and maximum-likelihood phylogenetic analyses. Colonies exhibited morphological features consistent with Sydowia spp., including melanized septate hyphae, chlamydospore-like structures, and catenate conidia. ITS and EF1-α sequence analyses supported assignment of the isolates to S. polyspora, with phylogenetic analyses placing Alabama isolates within the broader S. polyspora lineage alongside reference sequences from North America, Europe, and Asia. Species-specific amplification using the EF1-α primers SpolEF4F and SpolEF3R provided additional support for species identification. In a broader 2019–2021 survey across nine counties in Alabama, S. polyspora was recovered from 60% of surveyed stands. To our knowledge, this study represents the first peer-reviewed documentation of S. polyspora in Alabama. These findings identify S. polyspora as a widespread and common component of fungal communities associated with symptomatic loblolly pine needles in Alabama.