Isolation, Molecular Characterization and Growth Promoting Activity of Free Living Diazotrophs Screened from Soils of Lesotho

Abstract

Thirty six free living diazotrophic isolates represented from different soil pH (5 to 7.22) of Lesotho were characterized. A nitrogen free medium was used to screen nitrogen fixing diazotrophs. Strains were classified into three groups as Azospirillum, Azotobacter and Bacillus spp based on their biochemical and molecular characteristics. All the diazotrophic groups showed some degree of nitrogenase activity when assayed using acetylene (C2H2) reduction assay and production of Indole Acetic Acid (IAA) when screened for PGPR traits. Despite the strain variability, significantly higher nitrogenase activity (190.20 nmol/mL-1h-1) was exhibited by strain NUL3-2 (Azospirillum spp), which in contrary exhibited lower amount of IAA production (0.032 mg ml-1) compared to strain MAF7-1 (0.448 mg ml-1) from the group of Azotobacter spp. Further evaluation of strains efficacy for plant growth promotion activity is commendable under greenhouse experimentation for potential use of these strains as biofertilizer.