Diversity of ectomycorrhizal fungal communities across six Picea species grown in common gardens.

Host plant identity is a primary determinant of ectomycorrhizal (ECM) fungal diversity and community composition, but the effect of host identity within congeneric species and whether this effect varies with environmental changes remain unclear. In this study, we used ITS rRNA amplicon sequencing to assess the diversity and community composition of ECM fungi in the roots of six phylogenetically distinct spruce (Picea) species grown in three common gardens with varying environmental conditions. Our results showed that, although ECM fungal richness and Shannon diversity were similar among spruce species at each site, their ECM fungal community composition differed. The differences in ECM fungal community composition between paired spruce species were not significant at the wettest site, but were significant at two dry sites, with the main difference observed between P. asperata and other spruce species (p < 0.05). The Mantel test indicated a weak positive correlation between ECM fungal community composition differences and the phylogenetic distance among host species. Preferred spruce/ECM fungal species varied across the three sites, with the lowest preference ratio observed at the wettest site. Additionally, Sebacina, Trichophaea, and Wilcoxina were the dominant genera in spruce roots. These results highlight the significant role of host identity within congeneric species in ECM fungal community assembly in relatively dry environment, enhancing our understanding of how congeneric plants influence ECM fungal diversity and community composition.