Multilocus phylogenetic analysis revealed a new cryptic lineage of Serpula himantioides in Japan

Serpula himantioides is a widely distributed saprotrophic fungus that causes root and butt rot in various tree species. In Japan, butt rot associated with S. himantioides is observed in Chamaecyparis pisifera and Abies sachalinensis. Previous studies have shown that S. himantioides includes five phylogenetically defined cryptic lineages, but the placement of Japanese isolates remains unclear. To clarify the phylogenetic relationship between Japanese S. himantioides and the five known lineages, we conducted a phylogenetic analysis using three newly collected Japanese isolates along with 74 S. himantioides isolates, based on the internal transcribed spacer (ITS) region, the 28 S large subunit (LSU) rDNA, the beta-tubulin (tub) gene, and the heat stress protein (hsp) gene. The concatenated phylogenetic tree showed that Japanese isolates composed a clade with a high bootstrap value distinct from the known lineages, indicating the Japanese isolates present a new cryptic lineage of S. himantioides.