New Records of Willow Rust Caused by Melampsora laricis-epitea in Alaska, U.S.A., and on Salix atrocinerea in Spain

Community observations in Utqiaġvik, AK, noted symptoms of rust disease on dwarf willow ( Salix spp.). Morphological characteristics and sequencing analysis of infected leaves collected in July 2020 identified the rust as Melampsora laricis-epitea. DNA sequencing of the 28S rDNA region confirmed 99.89% identity with M. laricis-epitea isolates from North America and Europe. Comparative morphology and sequence analysis of Spanish specimens hosted at Purdue University's Arthur Fungarium (PUR) on Salix atrocinerea also matched M. laricis-epitea, representing the first confirmed record of this rust on this host in Spain. Our work extends the known range of M. laricis-epitea into Alaska and highlights its potential broader establishment across North America. Given the ecological and cultural significance of willows in Arctic ecosystems as well as their use in biomass cultivation, improved taxonomic resolution and monitoring of Melampsora species are essential for understanding their impacts and managing potential disease risks.