Abstract

Plant growth-promoting rhizobacteria (PGPR) are very important in the improvement of plant productivity and soil health. In spite of the common application of these PGPR as bioinoculants, it has not been adequately described how they affect the indigenous population of the soil microbial community. This paper examines the impact of two strains of PGPR mostly used, Pseudomonas aeruginosa and Burkholderia spp., on the rhizosphere bacterial community of tomato (Solanum lycopersicum) in the greenhouse. An experiment of pot with controlled conditions was carried out by inoculation of PGPR strains in tomato seedlings. Pre- and post-inoculation of soil samples was taken and subjected to 16S rRNA gene-based amplicon sequencing on the Illumina MiSeq platform. The QIIME2 and the Microbiome Analyst tools were used to analyze both taxonomic profiling, diversity analysis and core microbiome identification. The outcome identified bacterial diversity and community composition alterations to be evident due to the application of PGPR inoculation. There was an increase in taxonomic richness in beneficial genus such as Pseudomonas, Burkholderia, Bacillus, and Paenibacillus. As shown in beta diversity analysis of principal coordinate analysis, there was clear separation of the treated soils as compared to the control. It was also demonstrated that core microbiome and Venn diagrams further supported the finding that there was recruitment of unique operational taxonomic units in the PGPR-treated groups, although Burkholderia-inoculated soil had the greatest number of unique taxa. Such results show that the use of PGPR not only improves the abundance of friendly microbial populations but also redesigns the indigenous microbial structure of the tomato rhizosphere. This study confirms the strategic application of PGPR as a crop health enhancer and toward sustainable agriculture.

Key words: Soil Metagenomics, Rhizosphere, Greenhouse pot trial, Bacterial Community, Functional Annotation.