Exploration and Profiling of Potential Thermo-alkaliphilic Bacillus licheniformis and Burkholderia sp. from varied Soil of Delhi region, India and their Plant Growth-Promoting Traits

Soilless cultivation has emerged as a fundamental alternative for large-scale vegetable production because it generates high-quality yields and uses resources efficiently. While plant growth-promoting bacteria (PGPB) are known to enhance growth and physiological aspects in crops grown in soil, their application in soilless cultivation has been relatively less explored. This study aimed to isolate potential PGPBs from soil samples collected from five locations in and around the Delhi-National Capital Region (NCR), India, which were further screened for significant PGPB attributes. Among these, 51 isolated were selected for assessing the impact on Oryza sativa (rice) growth and yield grown on a hydroponic set. The results indicated that isolates AFSI16 and ACSI02 significantly improved the physiological parameters of the plants. For instance, treatment with AFSI16 showed a 23.27% increase in maximum fresh shoot mass, while ACSI02 resulted in a 46.8% increase in root fresh mass. Additionally, ACSI02 exhibited the highest shoot length (34.07%), whereas AFSI16 exhibited the longest root length (46.08%) in O.sativa. Treatment with AFSI16 also led to significant increases in total protein content (4.94%) and chlorophyll content (23.44%), while ACSI02 treatment showed a 13.48% increase in maximum carotenoid content in the leaves. The potential PGPBs were identified through 16S rRNA sequencing, as the two most effective strains, AFSI16 and ACSI02, belonged to thermo-alkaliphilic Bacillus licheniformis and Burkholderia sp., respectively. This study demonstrated the potential of these identified PGPB strains in enhancing crop performance, specifically in soilless cultivation systems.