Plant growth promoting activities of P solubilizing bacteria and their impact on disease resistance in groundnut, Arachis hypogaea L. against soil borne fungal pathogens

Abstract

Plant growth promoting (PGP) activities of soil bacteria directly help plants in taking up the nutrients, attuning the growth hormones and indirectly safeguard by inhibiting diverse groups of fungal pathogens. In this study, we explored the native P solubilizing bacteria (PSB) isolated from the acid soils (pH < 5.5) of Odisha for selection of efficient PGPR with antifungal potential. Five PSB strainswere checked for their P solubilization efficiencies with Ca3(PO4)2,AlPO4,FePO4 and Fe3(PO4)2. The bioconversion of P by all the five strains in the broth medium followed the order Ca-P > Fe(III)-P > Fe(II)-P >Al-P. The strains interestingly showed potential plant growthpromoting properties including indole acetic acid (IAA) andsiderophore production in in vitro tests. These five strains also exhibited antifungal activities against fungal pathogens(Pythium aphanidermatum, Fusarium oxysporum, Pythium debaryanum, Thanatephorus cucumeris and Aspergillus niger)of groundnut. A field study was carried out with two of the above PSB strains [identified as Bacillus amyloliquefaciens(KT633845) and Burkholderia cepacia (KT717633)] with groundnut. Both the stains significantly influenced the plantgrowth (plant height, nodule no. and nodule dry weight) and pod yield. However, these two strains inoculated along withdoses of inorganic phosphate (SSP, single super phosphate) resulted in significantly higher pod yield as well as residual soil P.Additionally; the prevalence of both seedling mortality and plant mortality due to collar rot and stem rot were found to bereduced significantly in the inoculated plots. The findings substantiate the growth promoting ability of the two P solubilizingstrains, and thus qualifies to be used as biofertilizers either alone or as components of INM practices