Targeted metagenome sequencing reveals the abundance of Planctomycetes and Bacteroidetes in the rhizosphere of pomegranate.

Abstract

Agricultural productivity of pomegranate can be enhanced by identifying the crop-associated microbial diversity in the rhizosphere region with respect to plant growth promoters and other beneficial organisms. Traditional culture methods have limitations in microbial screening as only 1-2% of these organisms can be cultured. In the present study, 16S rRNA amplicon-based metagenomics approach using MinION Oxford Nanopore platform was employed to explore the microbial diversity in the rhizosphere of pomegranate Bhagwa variety, across variable soil depths from 0 to 5 cms (R2), 5-10 cms (R4) and 10-15 cms (R6), using bulk soil as the control. Across all the three layers, significant variations in pH, nitrogen content and total fungal count were observed. 16S rRNA analysis showed the abundance of planctomycetes, Pirellula staleyi, followed by bacteroidetes, Flavisolibacter LC59 and Niastella koreensis across the various soil depths in the rhizospheric soil samples. Pathway prediction analysis indicated arginine and proline metabolism (gamma-glutamyl putrescine oxidase) and hydrogen sulfide biosynthesis as the most abundant pathway hits. Comparative abundance analysis across layers showed the R6 layer with the maximum microbial diversity in terms of highest dimension of variation (79.2%) followed by R4 and R2 layers (p < 0.01). Our analysis shows the significant influence of root zone in shaping microbial diversity. This study has reported the presence of Planctomycetes, Pirellula staleyi for the first time in the pomegranate field.