Biochemical and molecular characterization of DAPG-producing plant growth-promoting rhizobacteria (PGPR) of groundnut (Arachis hypogaea L.)

Abstract

Plant growth-promoting rhizobacteria (PGPR) thrive in the rhizosphere of plants and play a beneficial role in plant growth, and development along with biocontrol activities. The present study was undertaken with the aim of developing rhizobacterial inoculants for groundnut for enhancement of growth and yield and suppression of major soil-borne fungal diseases caused by Sclerotium rolfsii (stem rot) and Aspergillus niger (collar rot). Out of a total of 154 rhizobacterial isolates obtained from groundnut rhizosphere, 78 isolates were selected on the basis of in vitro antifungal activities against three major soil-borne fungal pathogens of groundnut, i.e. Aspergillus niger, Aspergillus flavus and Sclerotium rolfsii. The selected isolates were further screened for the production of 2,4-Diacetylphloroglucinol (2,4-DAPG) by the gene specific PCR amplification of phlD gene. A total of 11 rhizobacterial isolates were found to have DAPG-producing genes and selected for further studies. Gene specific primers were also used for characterization of the isolates for plant growth-promoting and biocontrol traits. The qualitative and quantitative estimation of the various attributes of the isolates were also carried out. Majority of the isolates showed production of IAA, siderophores and fluorescent pigments. The DAPG-producing rhizobacterial isolates have great potential as bio-inoculants for groundnut crop for suppressing soil-borne fungal pathogens and to enhance growth and yield.