Characterization of cultural beneficial bacterial diversity for plant growth promoting attributes associated with rice rhizosphere

ABSTRACT

Aim: The study was undertaken to isolate, characterize and molecularly identify plant growth promoting rhizobacteria (PGPR) associated with rice rhizosphere occurring in Gangetic plains of the country. Methodology: One hundred forty three plant growth promoting rhizobacteria were isolated on various culture media and characterized culturally and morphologically through Scanning Electron Microscope. These rhizobacterial isolates were further screened for plant growth promoting activities like HCN production, siderophore production and phosphate solubilisation. The 16S rDNA sequencing was done to decipher phylogenetic relationship among 19 selected PGPRs. Besides, these were also tested for anti-oxidative enzyme production to mitigate deleterious effects of various stresses on plant growth and metabolism. Results: Nineteen potential plant growth promoting rhizobacteria were characterized for plant growth promoting attributes and were indentified at molecular level. Rice is well colonized by bacteria mainly Bacillus spp., Pseudomonas spp., Burkholderia sp., and Acinetobactor spp., Rice seeds treated with microbial consortium of MAU 143 + MRT 84 recorded in increased antioxidant production–SOD activity (0.02 U mg−1 f.w.t.), POX activity (0.16 U mg−1 f.w.t.), POP activity (0.06 U mg−1 f.w.t.) and TPC assay (1.17 µg gallic acid mg-1 extract) which might have stimulated the growth of radical (2.2 cm) and plumule (1.6 cm) over control. These three PGPRs viz., MAU 143, MRT 84 and MRT 92 strain showed great potential to improve antioxidant and total polyphenol production and seed vigour of rice seedlings. The identified rhizobacterial strains may be used for plant growth promotion and improvement in nutrients mobilization and oxidative stresses in rice production. Interpretation: The study suggested that plant growth promoting rhizobacteria isolated from rice rhizosphere have greater potential to improve soil nutrients status while provide resistance against infection of pathogenic microbes due to production of anti-oxidative enzymes and phenolic compounds in rice seedlings.