Rhizosphere microbial community structure and diversity in canker-symptomatic and asymptomatic poplars

Abstract Poplar canker threatens the health and productivity of poplar plantations, but its association with the rhizosphere microbiome remains poorly resolved. We profiled bacterial 16 S V3-V4 and fungal ITS1 communities in root-zone soils from asymptomatic and canker-symptomatic Populus talassica at Qitai, Nileke, and Dabancheng, with three independent composite samples per site-by-status group. Bray-Curtis PERMANOVA detected effects of sampling site, disease status, and their interaction on bacterial and fungal community dissimilarity. Location-based dispersion analyses further indicated that these differences were driven by changes in community composition rather than solely by shifts in group centroids. While no overall differences in Shannon alpha diversity were observed between asymptomatic and canker-symptomatic trees after Benjamini-Hochberg correction, site-level differences were detected. Pseudomonadota was less abundant in diseased samples at all three sites, whereas statistical support for changes in Actinomycetota, Ascomycota, and Basidiomycota was site dependent. The FUNGuild Plant Pathogen category had a higher mean abundance in diseased samples at all sites but was significant only at Nileke after correction. Genus-level co-occurrence patterns also varied among sites and represent statistical associations rather than direct interactions. Nine independently recovered fungal isolates were identified as Botryosphaeria dothidea , a major causal agent of poplar canker, and the representative isolate XJAU23 fulfilled Koch’s postulates. In dual culture, a Streptomyces treatment restricted pathogen colony expansion at later observation times. These findings define site-dependent microbial patterns associated with poplar canker and identify experimentally validated organisms for further disease-control research.