Production of the alkaloid swainsonine by a fungal endophyte in the host Swainsona canescens.

Legumes belonging to the Astragalus, Oxytropis, and Swainsona genera have been noted by ranchers in the Americas, Asia, and Australia to cause a neurologic disease often referred to as locoism or peastruck. The toxin in these legumes is swainsonine, an α-mannosidase and mannosidase II inhibitor. Recent research has shown that in Astragalus and Oxytropis species swainsonine is produced by a fungal endophyte belonging to the Undifilum genus. Here Swainsona canescens is shown to harbor an endophyte that is closely related to Undifilum species previously cultured from locoweeds of North America and Asia. The endophyte produces swainsonine in vitro and was detected by PCR and culturing in S. canescens. The endophyte isolated from S. canescens was characterized as an Undifilum species using morphological and phylogenetic analyses.