Compartment-Specific Bacterial Communities in Turmeric and Their Association with Suppression of Ralstonia...

Bacterial wilt caused by Ralstonia pseudosolanacearum poses a significant threat to turmeric (Curcuma longa) production in many growing regions. Although plant-associated microbial communities may contribute to disease suppression, the ecological roles of rhizosphere and endosphere microbiomes in turmeric are still underexplored. Here, we characterized rhizosphere and endosphere bacterial communities using 16S rRNA gene amplicon sequencing and evaluated their antagonistic activity against the bacterial wilt pathogen of turmeric R. pseudosolanacearum strain RalsTur1. Microbiome profiling revealed compartment-specific patterns in turmeric-associated bacterial communities, with rhizosphere communities strongly structured by geographic location and endosphere communities comparatively stable across field sites. The endosphere core microbiome was dominated by bacterial members in the family Enterobacteriaceae, particularly Enterobacter, along with Pseudomonas, whereas rhizosphere communities included diverse taxa such as Bacillus and members of the Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium group. Interbacterial inhibition assays showed that several turmeric-associated isolates reduced RalsTur1 populations in vitro. However, in planta assays using tissue-cultured turmeric plants revealed that only the endosphere-derived bacterial community, including Chryseobacterium gleum (ED4), Pseudomonas laurentiana (ED4-21), and Pantoea sp. (WEH1), significantly reduced pathogen populations, resulting in a two-log reduction in pathogen abundance. These findings suggest that colonization within plant tissues may contribute to suppression of vascular pathogens and highlight endophytic bacteria as candidates for further investigation in microbiome-based management of bacterial wilt.