Exploring the role of beneficial soil microbiomes associated with mangroves of Kerala in India

Mangrove ecosystems are essential to coastal environments, providing a wide range of ecological functions. The current study intended to analyse diversity and distribution of beneficial microbial communities, including plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal (AM) fungi, associated with selected mangrove tree species in Kerala, India. Rhizosphere soil samples associated with the mangroves were found to be rich in AM fungal spores with the maximum of 420 spores/100 g of soil in Avicennia with the predominance of acaulospora species reflecting the influence of the acidic and nutrient-poor edaphic conditions. Additionally, the study characterized the isolated rhizosphere soil bacteria for biochemical characterization, primary screening for their antagonistic potentials against plant pathogens and secondary screening for PGPR characteristics. Biochemical characterization of the PGPR was carried out using various enzymatic and metabolic assays. The antagonistic potential of the PGPR was assessed against three plant pathogens, the isolate M. actin2 prominently inhibited 45% growth of F. oxysporium . The plant growth-promoting traits, such as IAA production, phosphate solubilization and nitrogen fixation, were recorded. The nursery experiment showed a maximum increment of 50% wet weight, 42% of dry weight, 72% of root length, 12% shoot length in treatment groups corresponding to control. The potential isolate M. actin2 was also identified using 16S rRNA gene sequencing and deposited in NCBI (MK660716). This study provides valuable insights into the diversity status of microbes in the mangrove soil of Kerala, emphasizing their potential significance in ecological processes and biotechnological applications.