Screening of Plant Growth-Promoting Rhizobacteria from Maize (Zea Mays) and Wheat (Triticum Aestivum)
Plant growth-promoting rhizobacteria (PGPR) are free-living soil-borne bacteria that colonize the rhizosphere and have great importance in governing the functional property of terrestrial ecosystems. In this study, rhizospheric bacteria were isolated from maize and wheat and screened for their plant growth promoting activities. These isolates were identified as Pseudomonas, Bacillus, Azospirillum and Azotobacter species. All isolates were tested for their indole acetic acid (IAA) production ability. All isolates produce the varying amounts of IAA ranging from 0.6-2.7 μg/ml. The highest concentration of IAA was produced by bacterial strain Bacillus subtilis AK31. A series of growth pouch and pot experiments were conducted to study the effect of bacterial inoculants on the growth of maize and wheat. It was concluded that IAA plays a key role in the growth promotion of roots in maize and wheat in growth pouch study. In maize, isolate AK1, AK21, AK31 and AK8 showed high indole acetic acid (6.86, 7.11, 7.11 and 7.36 pmol/ml, respectively) and root elongation activity (4.10, 5.00, 5.00 and 3.80 cm, respectively) after 96h of growth. In wheat, bacterial strains AK31, AK2, AK14, AK32 and AK15 showed high IAA (6.59, 5.66, 5.35, 7.53 and 5.66 pmol/ml, respectively) and root elongation (6.07, 4.00, 5.20, 6.90 and 5.20 cm, respectively) activity after 96h of growth. In pot experiments, Bacillus sp. AK21, Bacillus subtilis AK31, Azotobacter diazotrophicus AK14, Microbacterium sp. AK19 and Pseudomonas fluorescens AK32 showed effective results in terms of increase in root and shoot dry weight in maize (123, 130, 121, 120, 124g and 116, 126, 116, 114, 120g/pot, respectively) and wheat (130, 135, 125, 118, 140g and 105, 106, 110, 102, 110g/pot, respectively), in comparison to controls of maize and wheat crops. Thus, it might be concluded that PGPR strains AK21, AK31, AK14, AK19 and AK32 could be used as crop-enhancer and bio-fertilizer for production of maize and wheat.