Illumina 16S rRNA Gene Sequencing Dataset of Bacterial Communities of Soil Associated with Ironwood Trees ( Casuarina equisetifolia ) in Guam

Ironwood trees, which are of great importance for the economy and environment of tropical areas, were first discovered to suffer from a slow progressive dieback in Guam in 2002, later referred to as ironwood tree decline (IWTD). A variety of biotic factors have been shown to be associated with IWTD, including putative bacterial pathogens Ralstonia solanacearum and Klebsiella species ( K. variicola and K. oxytoca ), the fungus Ganoderma australe , and termites. Due to the soilborne nature of these pathogens, soil microbiomes have been suggested to be a significant factor influencing tree health. In this project, we sequenced the microbiome in the soil collected from the root region of healthy ironwood trees and those showing signs of IWTD to evaluate the association between the bacterial community in soil and IWTD. This dataset contains 4,782,728 raw sequencing reads present in soil samples collected from thirty-nine ironwood trees with varying scales of decline severity in Guam obtained via sequencing the V1–V3 region of the 16S rRNA gene on the Illumina NovaSeq (2 × 250 bp) platform. Sequences were taxonomically assigned in QIIME2 using the SILVA 132 database. Firmicutes and Actinobacteria were the most dominant phyla in soil. Differences in soil microbiomes were detected between limestone and sand soil parent materials. No putative plant pathogens of the genera Ralstonia or Klebsiella were found in the samples. Bacterial diversity was not linked to parameters of IWTD. The dataset has been made publicly available through NCBI GenBank under BioProject ID PRJNA883256. This dataset can be used to compare the bacterial taxa present in soil associated with ironwood trees in Guam to bacteria communities of other geographical locations to identify microbial signatures of IWTD. In addition, this dataset can also be used to investigate the relationship between soil microbiomes and the microbiomes of ironwood trees as well as those of the termites which attack ironwood trees.