In Vitro Screening for Abiotic Stress Tolerance and Biocontrol Ability of Plant Growth Promoting Strains of Azotobacter and Azospirillum spp.

Abstract

The selection and deployment of microorganisms in stressed ecosystems with biocontrol ability is a major challenge. In this investigation, we sought to isolate and identify strains of Azotobacter and Azospirillum spp., which could withstand abiotic stresses and possess the potential to serve as biological control against five phytopathogenic fungi. Stress tolerance was evidently less obvious in Azospirillum strains than in Azotobacter strains, when bacterial strains were screened for high temperature (50 °C), salt (7% NaCl), and drought (1.2 MPa). Strains Asp30 and Asp 32 of Azospirillum and Azb 19, Azb20 and Azb27 of Azotobacter were found tolerant to temperature, drought and salinity stresses. Five strains of Azotobacter viz. Azb2, Azb6, Azb10, Azb16 and Azb18 and six strains of Azospirillum viz. Asp2, Asp10, Asp22, Asp30, Asp32 and Asp39 inhibited all the five fungal phytopathogens studied. Therefore, in vitro screening provided the basis for identification and selection of strains with abiotic stress tolerance and biocontrol ability.