Endophytic Bacteria and Fungi Associated with Polygonum cuspidatum in the Russian Far East

<i>Polygonum cuspidatum</i>, alternatively known as <i>Fallopia japonica</i> or <i>Reynoutria japonica</i>, is a perennial herb belonging to the Polygonaceae family. Commonly called Japanese knotweed or Asian knotweed, this plant is native to East Asia, particularly in regions such as Korea, China, and Japan. It has successfully adapted to a wide range of habitats, resulting in it being listed as a pest and invasive species in several countries in North America and Europe. This study focuses on analysing the composition of the bacterial and fungal endophytic communities associated with Japanese knotweed growing in the Russian Far East, employing next-generation sequencing (NGS) and a cultivation-based method (microbiological sowing). The NGS analysis showed that the dominant classes of endophytic bacteria were Alphaproteobacteria (28%) and Gammaproteobacteria (28%), Actinobacteria (20%), Bacteroidia (15%), and Bacilli (4%), and fungal classes were Agaricomycetes (40%), Dothideomycetes (24%), Leotiomycetes (10%), Tremellomycetes (9%), Pezizomycetes (5%), Sordariomycetes (3%), and Exobasidiomycetes (3%). The most common genera of endophytic bacteria were <i>Burkholderia</i>-<i>Caballeronia</i>-<i>Parabukholderia</i>, <i>Sphingomonas</i>, <i>Hydrotalea</i>, <i>Methylobacterium</i>-<i>Metylorubrum</i>, <i>Cutibacterium</i>, and <i>Comamonadaceae</i>, and genera of fungal endophytes were <i>Marasmius</i>, <i>Tuber</i>, <i>Microcyclosporella</i>, <i>Schizothyrium</i>, <i>Alternaria</i>, <i>Parastagonospora</i>, <i>Vishniacozyma</i>, and <i>Cladosporium</i>. The present data showed that the roots, leaves, and stems of <i>P. cuspidatum</i> have a greater number and diversity of endophytic bacteria and fungi compared to the flowers and seeds. Thus, the biodiversity of endophytic bacteria and fungi of <i>P. cuspidatum</i> was described and analysed for the first time in this study.