Bhushan ShresthaChaudhari, Suraj2026-04-242026-04-242023https://hdl.handle.net/20.500.14540/26409Phosphorus (P) is a crucial growth-limiting plant nutrient that influences a variety of key metabolic processes in plants, including cell division and development, macromoleculabiosynthesis, photosynthesis, and respiration. It is typically advised to apply P fertilizer toincrease the soil's availability of P. Unfortunately, 75–90% of applied P fertilizers sooprecipitate as a result of Fe, Al, and Ca complexes present in the soil, making them unavailable to plants soon after application. An effective strategy for enhancing the soil's availability to plants is to employ PSB to release insoluble and fixed forms of P. This studwas undertaken to isolate effective phosphate solubilizing bacteria along with various plangrowth promoting traits. A total of 19 bacterial isolates were isolated from rhizosphere soof which 5 were selected for further study with the highest solubilization index. Studies oquantitative P solubilization of TCP and bone meal revealed increased solubilized concentration with days of incubation. At 15 days of incubation the highest solubilization oTCP was observed with isolate KP2 (73.59 µg/mL) followed by L2 (65.98 µg/mL).However case of bone meal solubilization maximum solubilization was observed with isolate L2 (4µg/mL) followed by KP2 (45 µg/mL) at 15 days of incubation. Reduction in pH of mediumduring both TCP and bonemeal solubilization was observed with increase in days oincubation. Upon 16s rRNA sequencing of most effective PSB isolate L2 was identified to bBurkholderia sp. Different PGP features were found with isolated PSBs. The most promisinisolate was L2, which possessed PGP characteristics such as zinc solubilization, nitrogenfixation, auxin synthesis, ammonia generation, and antifungal activity. Isolate SM1 displayePGP characteristics including nitrogen fixation, antifungal activity, ammonia generation, zinsolubilization, and cellulase synthesis. Different PGP characteristics were also present in thisolates KP2, KP3, and P1. The results of a greenhouse experiment using PSB isolate folettuce growth promotion showed that PSB had a beneficial effect on growth promotionThe most promising isolate was L2, which resulted in increased leaf area, root volume, andry biomass. Except for isolate SM1, other PSB isolates accelerated the growth of lettuce. Thus, we may recommend an efficient PSB isolate as a viable biofertilizer to be used toboost crop yields. Keywords: bio-control, IAA, nitrogen fixation, phosphate, phosphate solubilization, plan growth promotion, rhizobacteriaen-USBone phosphatePhosphate solubilizationThesis