P-329 - Investigating the Microbiome Shift in Ironwood Trees caused by Ralstonia Infection

Ralstonia solanacearum, the pathogen responsible for Ironwood Tree Decline (IWTD), has affected ironwood trees in Guam since 2002, causing ecological damage. Klebsiella and Pseudomonas are believed to contribute to IWTD, suggesting complex microbial interactions. This study investigates how R. pseudosolanacearum infection alters the microbial composition of ironwood trees. A total of 101 samples were collected from 40 ironwood trees across five diverse areas in Guam. Ralstonia was detected using Agdia Immunostrips, PCR, and qPCR. Sequencing of 16S rRNA and ITS regions was performed, and samples were analyzed using Illumina BaseSpace and QIIME2. Taxonomic analysis revealed a reduction in bacterial richness and diversity in Ralstonia-infected samples. The samples collected from shallow depth(0-7.62 cm) had a higher abundance of Ralstonia compared to those from deeper depth(10.16-17.78 cm). Beneficial microorganisms like Cellulomonas and Sporomusa were more common in uninfected trees. Principal Component Analysis showed distinct bacterial clusters driven by Ralstonia abundance. Fungal communities, dominated by Basidiomycota and Ascomycota, were influenced by Ganodermataceae abundance. These findings highlight how Ralstonia affects bacterial diversity, while fungal diversity is linked to specific fungal families. This provides insights into the microbial dynamics of IWTD, emphasizing the interaction between Ralstonia and microbial communities. This understanding could aid in developing targeted management strategies to control the pathogen by preserving the tree’s microbiome.